Distribution Characteristics of Fluorine in the Soil of Brick Tea Plantations in Chibi and the Sources of Pollution

Distribution Characteristics of Fluorine in the Soil of Brick Tea Plantations in Chibi and the Sources of Pollution | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Distribution Characteristics of Fluorine in the Soil of Brick Tea Plantations in Chibi and the Sources of Pollution Quan Li, Yang Li, Li Liu, Zhigang Li, Yi Chen, Qian Wang, Guoping Xia This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4766502/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Tea plants are known hyperaccumulators of fluorine and accumulate quantities of fluorine proportional to the concentration of fluorine in the environment. The primary source of fluorine in tea is water-soluble fluorine compounds in the soil, which tea plants readily absorb and accumulate in the leaves. Analyses of soil samples indicate that the parent material of soil significantly influences the total fluorine content. The distribution of fluorine in the surface soil of different soil types within the tea gardens follows this order: brown red soil > young red soil > yellow red soil. Generally, fluorine content in the surface soil of the planting area displays a decreasing trend from north to south. Under acidic conditions, pH variations minimally impact the concentration of water-soluble fluorine in the soil. Exogenous sample analyses reveal that the primary sources of soil fluorine are geological formations and the prolonged and intensive use of foreign and Western compound fertilizers. Atmospheric deposition, along with water used for irrigation and pesticides in tea gardens, do not constitute significant sources of fluorine in the surface soil. To mitigate fluorine levels in brick tea, it is advisable for tea gardens to increase the use of organic and nitrogen-based fertilizers while decreasing reliance on compound fertilizers. Soil Brick Tea Fluorine Geological Strata Compound Fertilizer Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Highlights The distribution of fluoride content follows the sequence of red soils > young red soils > yellow-red soils. pH fluctuations have a minimal impact on the water-soluble fluoride content in the soil under acidic conditions. The geological stratum is a primary source of fluoride in the soil. Fertilizers significantly contributes to elevated fluoride content in the soil. 1. Introduction The average fluorine concentration in the surface soil of China stands at 453 mg/kg, ranging from 191–1012 mg/kg, significantly exceeding the average global soil fluorine concentration of 200 mg/kg(China National Environmental Monitoring Station.1990). Research reveals a distinct regional pattern in China's soil fluorine content, with higher concentrations in the north compared to the south, vastly surpassing the global norm. The arid, scant rainfall conditions in the northwest region lead to minimal weathering and leaching, causing fluorine to be less mobile and thus maintaining higher soil fluorine levels. Conversely, in the southeastern coastal provinces, strong leaching coupled with high soil acidity facilitates the mobilization and leaching of fluorine, resulting in lower concentrations. The average fluorine content in the red soils of the southern regions is 65.6 mg/kg, while in the yellow and grey soils of the North China region, it averages 430.46 mg/kg (Li Xiaoliang et al. 2010 ; Yi chunyao et al. 2013). Hubei Province's 2023 soil geochemical background data indicate an average fluorine content of 561 mg/kg in the surface soil of Chibi City(Xiang Jianqiao et al. 2023 ). The primary regions for brick tea production in China are Hubei, Hunan, Sichuan, Yunnan, and Shaanxi. Studies indicate that tea plants (871–2000 mg/kg) and camellias (1000–1400 mg/kg) naturally accumulate high quantities of fluorine(CAMARENA-RANGEL N et al. 2015; SHU W S et al. 2003). Tea plants, in particular, are hyperaccumulators, containing 10–100 times more fluorine than other plants in the same settings. The fluorine accumulation in tea plants is in direct proportion to environmental fluorine concentration(Ruan J et al. 2023), and the fluorine in tea predominantly originates from the soil. Factors such as soil pH, along with other cations and anions, influence fluorine absorption by plants. When the soil pH is between 5.5 and 6.5, plant uptake of soil fluorine is minimal(Weinstein L H et al. 2004). The bioavailability of fluorine in soil is determined by its chemical forms rather than its total content(Moirana R L et al. 2021). Fluorine exists in various forms in the soil, such as water-soluble, exchangeable, iron-manganese bound, organically bound, and residual(Gao H et al. 2012 ). The distribution of fluorine content in different soil layers typically follows the order: residual > exchangeable > water-soluble > organic > amorphous iron oxide(Gan C D et al. 2020). Residual fluorine, which makes up over 90% of the total fluorine content, is the predominant form found in the soils of tea gardens. Water-soluble fluorine represents only 0.03%-0.44% of the total fluorine content. Both water-soluble and total fluorine levels in tea garden soils tend to decrease with increasing depth(Wu Weihong et al. 2002 ). Additionally, water-soluble and exchangeable fluorine are readily available to plants, animals, microbes, and humans, being easily absorbed by crop roots and subsequently entering the food chain(Hong P et al. 1993 ; Xie Z M et al. 1999). The presence of water-soluble fluorine in soil is influenced by factors such as organic matter, parent material, soil texture, pH, and climatic conditions. Notably, groundwater pH significantly affects water-soluble fluorine levels; within a pH range of 6.0-8.5, each incremental increase of 0.5 in soil pH can raise the water-soluble fluorine content by 0.4–0.5 mg/kg(Xia Jingfen et al. 2009 ). There is a positive correlation between the exchangeable and water-soluble fluorine in the soul and the total amount of cation exchange and organic matter in the soil. Given the high fluorine content in Chibi brick tea and the lack of comprehensive research on the distribution and sources of fluorine in this region's soil, this project employs specialized methods such as 1:10,000 hydrogeological, ecological environment geological surveys, atmospheric deposition monitoring, soil geochemical measurements, and vertical soil profile analysis. Samples of typical surface soil, different types of soil, fertilizers, and water quality from the Chibi brick tea planting areas are collected and tested to explore the correlations between key indicators. This study aims to characterize the distribution and identify the pollution sources of fluorine in the typical brick tea planting soils of Chibi, as well as assess the risk to the environmental quality of the surface soil in these tea gardens. 2. Materials and Methods 2 .1 . Soil Sample Collection The layout and sampling methods for the project sites adhere to the "Specifications for Geochemical Evaluation of Land Quality" (DZ/T0295-2016). A total of 37 soil parent rock samples were collected, each weighing between 2.0-3.0 kg. The sampling density for surface soil samples was set at 50 points/km², resulting in 260 samples collected, each weighing between 1.0 kg and 1.5 kg, at a sampling depth of 0-20 cm. The sampling density for soil form samples was approximately 7 points/km², with 30 samples collected, each also weighing 1.0 kg-1.5 kg, at the same sampling depth. Soil vertical profiles were established based on different soil types, totaling 4 profiles. The profile depth ranged from 1.5-2.0 m, with 4 samples systematically collected from top to bottom at each profile location according to the distinct soil horizons, totaling 16 samples. For the 36km 2 survey area, water quality samples were sourced from ponds, reservoirs, and wells, with a sampling density of approximately 1 point/2km 2 , resulting in 20 samples, each with a volume of 3-5 L. The sampling density for atmospheric dry and wet deposition was set at 1 point/12km 2 , with 3 atmospheric deposition monitoring stations established, and samples collected semi-annually, including 6 samples each of atmospheric dust and precipitation. The sampling locations are depicted in Figures 1 and 2. 2.2. Experimental Instruments Instruments include a PXSL-216F type ion meter, Leici PHSJ-4A pH meter, a balance, soil nutrient tester, mortar, Muffle furnace, and a reciprocating horizontal oscillating bed. 2.3. Sample Analysis Methods Total fluorine content in the soil is determined according to GB/T 22104-2008 "Soil Quality - Determination of Fluoride with Ion-selective Electrodes". Soil pH is measured using a potentiometric method with a soil to water ratio of 2.5:1. Soil ammonium nitrogen, available potassium, available phosphorus, and organic matter are quantified using the Ruilong brand soil nutrient tester. Various forms of fluorine in the soil are extracted and quantified through the Tessier five-step sequential leaching method. The leaching toxicity of soil fluorine is assessed based on the "Solid Waste - Leaching Toxicity Sulphuric Acid & Nitric Acid Method." 2.4. Data Processing Data analysis is performed using Excel 2016, Origin2017 mapping software, and SPSS statistical software for correlation analysis. 3. Results and Discussion 3.1. Geochemical Characteristics of Soil Fluorine and Influencing Factors 3.1.1 Influence of Soil Parent Rock Material on Soil Fluorine Content The type of parent rock material plays a crucial role in determining the total fluorine content in soil. The parent rock, which is the original rock from which the soil is derived, influences the soil's chemical properties through its chemical and mineral compositions, thereby significantly affecting the fluorine content(Hong P et al. 1993 ). Survey results indicate that the fluorine content in the silty claystone of the Shipai Formation is substantially higher than in silty shale, likely due to differences in mineral composition. Clay minerals are known for their strong adsorption capacity, enabling them to bind fluoride ions in the soil. Additionally, the layered structure of these minerals provides numerous adsorption sites for fluoride ions, thereby increasing the soil's fluorine concentration. Conversely, dolomite and limestone, primarily composed of calcium carbonate and magnesium-containing minerals, respectively, exhibit weaker adsorption capacities for fluoride ions, which results in lower fluorine content in these soils. The fluorine content of the various rocks is detailed in Table 1 . According to the data in Table 2 , the average fluorine content in surface soils of different types in the region's tea gardens ranks as follows: brown red soil > young red soil > yellow red soil, as illustrated in Table 2 . The formation process of brown red soil involves organic matter accumulation, clayification, desilication, and alumination. Consequently, the brown red soil in Chibi tea gardens is rich in Al 3+ , which readily reacts with F - to form aluminum fluoride complexes. This reaction enhances the soil's capacity to adsorb fluorine, thereby increasing its fluorine content. Table 1 Soil Fluorine Content in Different Parent Rocks No. Sample ID Geological Background Rock Type F mg/kg No. Sample ID Geological Background Rock Type F mg/kg 1 CJK-1 Xintan Formation Siltstone 829 19 CJK-7 Shipai Formation Silty claystone 819 2 CJK-2 Xintan Formation Siltstone 694 20 CJK-10 Shipai Formation Silty claystone 816 3 CJK-3 Xintan Formation Siltstone 745 21 CJK-11 Shipai Formation Silty claystone 812 4 CJK-4 Xintan Formation Siltstone 742 22 CJK-12 Shipai Formation Silty claystone 900 5 CJK-5 Xintan Formation Siltstone 696 23 CJK-13 Shipai Formation Silty claystone 922 6 CJK-6 Xintan Formation Siltstone 736 24 CJK-14 Shipai Formation Silty claystone 742 7 CJK-8 Xintan Formation Siltstone 800 25 CJK-15 Shipai Formation Silty claystone 745 8 CJK-9 Xintan Formation Siltstone 879 26 CJK-18 Shipai Formation Siltstone 227 9 CJK-27 Xintan Formation Siltstone 628 27 CJK-19 Shipai Formation Siltstone 230 10 CJK-28 Xintan Formation Siltstone 611 28 CJK-20 Shipai Formation Siltstone 151 11 CJK-29 Xintan Formation Siltstone 664 29 CJK-21 Shipai Formation Siltstone 169 12 CJK-30 Xintan Formation Siltstone 708 30 CJK-22 Shipai Formation Siltstone 191 13 CJK-33 Xintan Formation Siltstone 733 31 CJK-23 Shipai Formation Siltstone 128 14 CJK-34 Xintan Formation Siltstone 713 32 CJK-24 Shipai Formation Siltstone 190 15 CJK-35 Xintan Formation Siltstone 763 33 CJK-25 Shipai Formation Siltstone 157 16 CJK-32 Baota Formation Limestone 500 34 CJK-26 Shipai Formation Siltstone 190 17 CJK-16 Loushanguan Formation Dolomite 236 35 CJK-31 Longmaxi Formation Silty claystone 787 18 CJK-17 Loushanguan Formation Dolomite 300 36 CJK-36 Longmaxi Formation Silty claystone 793 37 CJK-37 Longmaxi Formation Silty claystone 641 Table 2 Soil Fluorine Content in Different Parent Materials Soil Type Unit Brown Red Soil Yellow Red Soil Young Red Soil Sample Quantity pcs 113 75 12 Minimum Value mg/kg 408 349 502 Maximum Value mg/kg 946 742 718 Average Value mg/kg 574 529 566 Area mu 339226 225150 36024 Area Proportion % 56.5 37.5 6 3.1.2 Correlation Analysis of Soil Water-Soluble Fluorine Content and Total Fluorine Content In this study, 30 surface soil samples from 0–20 cm depth in tea gardens were analyzed for both water-soluble and total fluorine content. The soil fluorine content in the tea gardens ranged from 349–946 mg/kg, with an average of 552 mg/kg. The water-soluble fluorine content varied from 0.85 to 10.12 mg/kg, averaging 2.66 mg/kg, which represents 0.15–1.41% of the total fluorine content, as shown in Table 3 . A correlation analysis conducted using SPSS software yielded a correlation coefficient (r) of 0.41 and p < 0.05 with n = 30, indicating a modest positive correlation between the water-soluble and total fluorine content. Table 3 Soil Sample Test Results Sample ID Water-Soluble Fluorine (mg/kg) Total Fluorine (mg/kg) Water-Soluble Fluorine/Total Fluorine (%) pH Sample ID Water-Soluble Fluorine (mg/kg) Total Fluorine (mg/kg) Water-Soluble Fluorine/Total Fluorine (%) pH CBXT-01 2.20 494.90 0.44 4.20 CBXT-16 1.76 594.10 0.30 3.95 CBXT-02 3.93 795.60 0.49 4.56 CBXT-17 1.90 777.90 0.24 3.70 CBXT-03 2.04 553.20 0.37 4.11 CBXT-18 1.69 702.80 0.24 3.92 CBXT-04 1.78 501.20 0.35 4.22 CBXT-19 1.67 696.60 0.24 4.16 CBXT-05 1.90 551.10 0.35 4.45 CBXT-20 2.31 685.20 0.34 4.28 CBXT-06 1.82 535.10 0.34 5.60 CBXT-21 4.09 598.07 0.68 4.65 CBXT-07 1.72 544.60 0.32 4.17 CBXT-22 1.05 580.60 0.18 4.09 CBXT-08 2.56 581.50 0.44 4.02 CBXT-23 7.79 742.30 1.05 3.88 CBXT-09 2.53 565.20 0.45 3.90 CBXT-24 6.88 650.95 1.06 4.25 CBXT-10 2.35 590.60 0.40 4.03 CBXT-25 0.86 376.90 0.23 4.18 CBXT-11 1.99 573.60 0.35 4.16 CBXT-26 0.86 420.78 0.20 4.39 CBXT-12 10.12 718.00 1.41 4.53 CBXT-27 5.19 676.25 0.77 4.58 CBXT-13 1.72 587.20 0.29 3.91 CBXT-28 1.32 463.84 0.28 4.23 CBXT-14 1.69 652.50 0.26 4.23 CBXT-29 1.40 526.70 0.27 3.73 CBXT-15 1.75 945.70 0.19 3.92 CBXT-30 0.85 551.82 0.15 3.87 3.1.3 The Influence of Soil pH on the Forms of Water-Soluble Fluoride in Soil In this study, 30 samples of 0–20 cm surface soil from the tea gardens were collected. The soil pH ranged from 3.70 to 5.60, with an average value of 4.20. A correlation analysis between the water-soluble fluoride content and soil pH in these soils revealed that within the pH range of 3.70–3.95, no significant correlation was observed between water-soluble fluoride content and soil pH (r = 0.09, P > 0.05, n = 9). However, within the pH range of 4.02–5.60, a weak positive correlation was found (r = 0.20, P > 0.05, n = 21). This weak correlation may be due to competitive adsorption between hydroxide (OH-) and fluoride (F-) ions on clay minerals, which have similar ionic radii. As soil pH decreases, the release of OH- increases, thereby enhancing the soil’s ability to adsorb fluoride and reducing the content of water-soluble fluoride. 3.2 Distribution Patterns of Fluoride in the Soil of Tea Fields 3.2.1 Horizontal Distribution Patterns Utilizing software for the management and maintenance of geochemical survey data and land quality assessment, fluoride content values were assigned to each evaluation unit within the tea garden areas. Adhering to the "Geochemical Evaluation Standards for Land Quality" (DZ/T0295-2016), the soil fluoride levels in each evaluation unit were categorized as per the classifications detailed in Table 4 . The soil fluoride categorization results in the tea gardens are depicted in Table 5 . Regarding spatial distribution, there is a general trend of decreasing surface soil fluoride content from north to south, as illustrated in Figs. 3 and 4. Table 4 Soil Fluorine Classification Index Range >700 550–700 500–550 400–500 ≤ 400 Index Level First Level Second Level Third Level Fourth Level Fifth Level Abundance-Deficiency Level Extremely Abundant Abundant Moderate Marginal Lacking Note: The grading standards are based on the "Specifications for Geochemical Evaluation of Land Quality" (DZ/T0295-2016). Table 5 Fluoride Level Classification Results in Tea Garden Soil Number Index Range Index Level Abundance-Deficiency Level Exceedance Level Area (mu) Percentage (%) 1 >700 First Level Extremely abundant Not exceeding standard 37 0.62 2 550–700 Second Level Abundant Not exceeding standard 2290 38.13 3 500–550 Third Level Moderate Not exceeding standard 2027 33.76 4 400–500 Fourth Level Marginal Not exceeding standard 1571 26.17 5 ≤ 400 Fifth Level Lacking Not exceeding standard 79 1.32 Total 6004 100.00 3.2.2 Vertical Distribution Patterns Soil vertical profiles are organized according to different soil types, with a total of four profiles, labeled CBCP-01 to CBCP-4, with depths ranging from 1.5 to 2.0 meters. At each profile location, four soil samples are sequentially collected from the top downward, each representing a distinct soil horizon. As depicted in Fig. 5, the topsoil layer (0-20cm) and the deep subsoil layer (below 140cm) exhibit higher fluoride content. The intermediate soil layer (20-140cm) shows relatively lower fluoride content. This pattern can be attributed to several factors: the topsoil experiences secondary fluoride enrichment and receives additional fluoride from fertilizers, leading to elevated levels; fluoride migration from the deeper layers to the topsoil, combined with the long-term absorption of fluoride by tea tree roots, results in diminished fluoride levels in the intermediate layers; and the naturally high fluoride content in the parent material of the tea garden, which dissolves and migrates to the deeper soil layers during soil formation, contributes to the higher fluoride levels observed in these areas. 3.3 Analysis of the Material Sources of Soil Fluoride 3.3.1 Characteristics of Fluoride Changes from Atmospheric Deposition Fluoride in the atmosphere primarily exists as aerosols, which diffuse and mix thoroughly with various atmospheric components. Atmospheric fluoride then settles on the earth's surface or is washed down by rainfall, integrating into the soil. 3.3.1.1 Atmospheric Dry Deposition In the first evaluation area, Yiyang Bridge Tea Plantation and its surroundings, atmospheric dry and wet deposition monitoring stations were established on August 21, 2022 and March 17, 2023 (CBDQ-01, CBDQ-02), with biannual sampling resulting in four collections. In the second evaluation area, Bawang Temple Tea Plantation, a monitoring station (CBDQ-03) was set up on March 17, 2023, with biannual sampling amounting to two collections. The analysis of the elemental content in atmospheric dust is detailed in Table 6 , while the characteristics of these elements in the two evaluation areas are presented in Tables 7 and 8 . Table 6 Analysis of Element Content Characteristics in Atmospheric Dust at Monitoring Points #1 and #2 Element CBDQ-01(1#) CBDQ-02(2#) Maximum Minimum Average Soil Average K Maximum Minimum Average Soil Average K As 19.8 10 14.90 20.4 0.73 14.47 2.69 8.58 20.4 0.42 Hg 0.52 0.17 0.35 0.087 4.02 0.05 0.02 0.03 0.087 0.38 Cr 276 55.1 165.55 112.3 1.47 24.1 5.96 15.03 112.3 0.13 Cd 3.89 2.6 3.25 0.086 37.79 2.81 0.74 1.78 0.086 20.67 Pb 273 129 201.00 34.4 5.84 69.7 19.19 44.44 34.4 1.29 F 646 292 469.00 552 0.85 116 Not detected / 552 / Note: Content unit mg/kg, K = average value of atmospheric dust elements in the evaluation area/average value of soil elements in the evaluation area Table 7 Analysis of Element Content Characteristics in Atmospheric Dust in Evaluation Area One Element Maximum Minimum Average Soil Average K As 19.8 2.69 11.74 20.4 0.58 Hg 0.52 0.02 0.19 0.087 2.17 Cr 276 5.96 90.29 112.3 0.80 Cd 3.89 0.74 2.51 0.086 29.20 Pb 273 19.19 122.72 34.4 3.57 F 646 Not detected / 552 / Note: Content unit mg/kg, K = average value of atmospheric dust elements in the evaluation area/average value of soil elements in the evaluation area Table 8 Analysis of Element Content Characteristics in Atmospheric Dust in Evaluation Area Two Element Maximum Minimum Average Soil Average K As 10.48 4.51 7.49 20.4 0.37 Hg 0.097 0.01 0.05 0.087 0.62 Cr 26.7 6.87 16.78 112.3 0.15 Cd 2.8 0.56 1.68 0.086 19.53 Pb 62.3 15.60 38.95 34.4 1.13 F 152 Not detected / 552 / Note: Content unit mg/kg, K = average value of atmospheric dust elements in the evaluation area/average value of soil elements in the evaluation area 3.3.1.2 Atmospheric Wet Deposition Atmospheric precipitation samples are collected concurrently with atmospheric dust samples. Rainfall, a crucial aspect of atmospheric deposition, undergoes complex chemical reactions as it descends from the clouds to the ground. These reactions are influenced by both natural and anthropogenic chemicals in the atmosphere, altering the chemical composition of the rainwater and facilitating the migration and dispersion of heavy metals. Consequently, rainfall serves as a primary mediator of the geochemical cycle of materials. The analysis of heavy metal pollutants and pH values for 2021–2023 in the evaluation area is presented in Table 9 . Notably, at monitoring point CBDQ-01 (1#), the minimum pH recorded is 3.18, which falls below the standards set in the 'Environmental Technical Conditions for Tea Production Areas (NYT 853–2004)'. However, the levels of As, Hg, Cr, Cd, Pb, and F elements within the evaluation area comply with the NYT 853–2004 standards. This pH discrepancy is suspected to be caused by emissions from nearby tea processing factories, which release sulfur dioxide from coal combustion, subsequently dissolving into the rainwater and reducing its pH value. Table 9 Analysis of the Main Element Content in Atmospheric Precipitation at Each Monitoring Point in the Evaluation Area Element CBDQ-01(1#) CBDQ-01(2#) CBDQ-01(3#) Standard value Maximum Minimum Average Maximum Minimum Average Maximum Minimum Average As 1.4 0.5 0.95 0.61 0.48 0.54 7.88 0.86 4.37 100.00 Hg 0.06 Not detected / 0.06 Not detected / 0.09 Not detected / 1.00 Cr 0.55 0.37 0.46 1.32 1.24 1.28 2.45 1.13 1.79 100.00 Cd 0.36 0.23 0.30 0.08 Not detected / 0.06 Not detected / 5.00 Pb 1.01 0.15 0.58 1.13 0.17 0.65 0.46 Not detected / 100.00 F 0.243 0.04 0.14 0.127 0.078 0.103 0.159 0.071 0.115 2.00 pH 6.86 3.18 5.02 7.75 6.70 7.23 7.60 6.62 7.11 5.5–7.5 Note: As-Pb content unit is µg/L, F- content unit is mg/L, pH is dimensionless. Standard values refer to 'Environmental Technical Conditions for Tea Production Areas (NYT 853–2004)' 3.3.1.3 Classification The sum of the annual flux of atmospheric dry and wet deposition is calculated by adding together the fluxes from the first and second halves of the year. These details are depicted in Tables 10 and 11 . According to the 'Standards for Geochemical Evaluation of Land Quality' (DZ/T0295-2016), classification indices for atmospheric dry and wet deposition fluxes focus on the indicators for Cd and Hg. Division standard values are provided in Table 12 . Table 10 Atmospheric Dry and Wet Deposition Flux Table for Evaluation Area One Element Six-month deposition flux (mg·m − 2 ·a − 1 ) Annual flux (mg·m − 2 ·a − 1 ) First half of the year Second half of the year Dry Wet Dry Wet As 0.1736 0.1328 0.0934 0.1615 0.5613 Hg 0.0031 0.0099 0.0023 / 0.0153 Cr 1.2899 0.1755 1.2279 0.2912 2.9845 Cd 0.1210 0.0248 0.0176 0.0423 0.2057 Pb 3.4969 0.0274 1.2196 0.3484 5.0923 F 6.4149 25.9053 2.8686 18.5876 53.7764 Table 11 Atmospheric Dry and Wet Deposition Flux Table for Evaluation Area Two Element Six-month deposition flux (mg·m − 2 ·a − 1 ) Annual flux (mg·m − 2 ·a − 1 ) First half of the year Second half of the year Dry Wet Dry Wet As 0.5259 0.4319 0.0208 4.2326 5.2112 Hg 0.0113 0.0449 0.00002 / 0.0562 Cr 3.1137 1.2292 0.0136 0.6065 4.9630 Cd 0.3265 0.0316 0.0011 / 0.3592 Pb 7.2652 / 0.0309 0.2493 7.5454 F 17.7258 35.6356 / 85.4186 138.78 Table 12 Standard Values for Environmental Geochemical Grades of Atmospheric Dry and Wet Deposition Flux Evaluation Indicator Annual flux(mg∙m − 2 ∙a − 1 ) Level First Level, digital code is 1 Second Level, digital code is 2 Cd ≤ 3 > 3 Hg ≤ 0.5 > 0.5 Referring to Table 11 , the annual atmospheric dry and wet deposition flux of Cd in evaluation area one amounts to 0.2057 mg/(m²∙a), and Hg to 0.0153 mg/(m²∙a), both significantly below the level 1 grade standard values. The pH values of atmospheric precipitation in this area range from 3.18 to 7.75, typically acidic. The Cd and Hg environmental geochemical levels and overall grades of atmospheric dry and wet deposition flux in this area are categorized as grade 1. Similarly, the annual atmospheric dry and wet deposition flux of Cd in evaluation area two is 0.3592 mg/(m²∙a), and Hg is 0.0562 mg/(m²∙a), also considerably below the level 1 grade standard values. The pH values of atmospheric precipitation here range between 6.62 and 7.60. The Cd and Hg environmental geochemical levels and overall grades of atmospheric dry and wet deposition flux in this area are also classified as grade 1. The daily average values of atmospheric fluoride in both areas are 1.47 µg/(dm²∙d) and 3.80 µg/(dm²∙d), respectively, adhering to the 'Environmental Technical Conditions for Tea Production Areas' (NYT 853–2004) standard of 5.0 µg/(dm²∙d), indicating that atmospheric deposition does not contribute to the fluoride content in the topsoil of the tea gardens. 3.4 Characteristics of Fluoride Variation in Irrigation Water Water plays a pivotal role as the principal driving force and carrier of fluoride transfer in soil. During the survey, 20 irrigation water samples were collected from reservoirs, ponds, and wells near the tea gardens. These samples underwent analyses for pH, fluoride, and heavy metal content, with the results detailed in the following table. Notably, the highest recorded mercury content was 0.008 mg/L, which surpasses the limit set by the 'Environmental Technical Conditions for Tea Production Areas' (NYT 853–2005) by sevenfold. Out of the samples, four exceeded this mercury threshold, representing a 20% exceedance rate; the highest cadmium content reached 0.04027 mg/L, also exceeding the NYT 853–2004 standard by seven times, with eight samples also exceeding the cadmium threshold, resulting in a 40% exceedance rate; pH levels ranged from 6.86 to 8.76, with five samples surpassing the NYT 853–2004 threshold, an exceedance rate of 25%. However, the content of fluoride and heavy metals such as arsenic, lead, and chromium all complied with the NYT 853–2004 standards, indicating that irrigation water is not a significant source of fluoride in the topsoil of the tea gardens. Table 13 Statistical Table of Test Results for Tea Garden Irrigation Water Samples (unit: mg/L) Analysis item Minimum Maximum Average Standard value As 0.0005 0.0150 0.0022 0.1000 Hg 0.00007 0.00800 0.00106 0.00100 Cd 0.00002 0.04027 0.00574 0.00500 Pb 0.0004 0.0117 0.0019 0.1000 Cr6+ 0.001 0.004 0.003 0.100 F 0.075 0.163 0.120 2.000 pH (dimensionless) 6.86 8.76 7.42 5.5–7.5 Note: Standard values refer to 'Environmental Technical Conditions for Tea Production Areas' (NYT 853–2004). 3.5 Characteristics of Fluoride in Fertilizers Fertilizers are extensively used in agricultural settings to enhance crop yields. However, the impact of fertilizers on fluoride ions in soil is not well-understood. Fluoride ions are absorbed and transported through dissolution into soil, interactions with soil salts, and contact with root exudates. Fertilizer application modifies soil properties, making the study of fluoride ion bioavailability in soil crucial. Research by R.L. Moirana et al. indicates that the application of urea, diammonium phosphate, and organic fertilizers significantly increases the concentration of water-soluble fluoride (Ws-F) in the soil, while the levels of exchangeable fluoride (Ex-F) and fluoride associated with iron/manganese (Fe/Mn-F) remain relatively unchanged(Moirana R L et al. 2021). Thus, fertilizers primarily influence the concentration of water-soluble fluoride in the soil. Further research by Li Rongjuan in 2011 noted that the primary tea varieties in Sichuan—Fuzhuan, Kangzhuan, and Jinjian—had average fluoride contents of 989 mg/kg, 765 mg/kg, and 856 mg/kg, respectively, significantly exceeding the 300 mg/kg limit set by the 'Fluoride Content in Brick Tea' (GB 19965 − 2005)(Li Rongjuan 2013). In that year, the primary fertilizers used in Sichuan tea gardens included ammonium bicarbonate, urea, ammonium nitrate, ammonium sulfate, potassium sulfate, and potassium nitrate, with fluoride contents ranging from 22,500 to 45,600 mg/kg. The high fluoride levels in these chemical fertilizers have contributed to the high fluoride content in the surface soil of tea gardens. The Chibi ten-thousand-mu tea garden predominantly utilizes Yangfeng and Western compound fertilizers, along with organic fertilizers. Typical application rates are 50–100 kg/(mu∙season) for compound fertilizers and 100–300 kg/(mu∙season) for organic fertilizers. This project analyzed four samples of compound fertilizers and two samples of organic fertilizers, finding that their pH values and the levels of cadmium, mercury, arsenic, lead, and chromium all comply with the 'Limits of Harmful Substances in Fertilizers' (GB38400-2019), as presented in Table 4 – 10 . Compared to organic fertilizers, compound fertilizers contain significantly higher fluoride levels, ranging from 8,600 to 13,300 mg/kg, with an average of 10,950 mg/kg—nearly 20 times the average soil fluoride content of 349–946 mg/kg. The annual fluoride contribution from using Yangfeng and Western compound fertilizers in the tea gardens amounts to 2,579-7,976 mg/(m²∙year), with an average of 5,278 mg/(m²∙year). Given these findings, it is advisable for tea gardens to increase their use of organic and nitrogen-based fertilizers and decrease their reliance on compound fertilizers to reduce the fluoride levels in brick tea. Table 14 Test Results of Tea Garden Fertilizers (unit: mg/kg) Item Compound Fertilizer Organic Fertilizer CBFL-01 CBFL-02 CBFL-03 CBFL-04 Standard value CBFL-05 CBFL-06 Standard value pH 6.12 6.17 6.6 6.72 5.5–8.5 6.68 7.02 5.5–8.5 Cd 0.52 0.52 0.28 0.31 10 1.09 1.24 3 Cr 12.5 12 6.23 6.25 500 23.3 31.4 150 Pb 1.01 0.55 0.66 0.68 200 34.4 33.7 50 As 18.5 17.6 16.7 16 50 6.26 8.46 15 Hg 0.009 0.011 0.053 0.025 5 0.074 0.1 2 F 13200 13300 8600 8600 / 410 500 / Note: Standard values refer to 'Limits of Harmful Substances in Fertilizers' (GB38400-2019). 3.6 Characteristics of Fluoride in Pesticides In the Chibi ten-thousand-mu tea garden, the main fluoride-containing pesticides utilized include the herbicide oxyfluorfen phosphorus ammonium and the insecticide fluopicolide pymetrozine. The active components in the herbicide are phosphorus ammonium at 24% and ethoxyfluorfen at 8%, resulting in a fluoride content of 0.42% (i.e., 4.2 mg/kg). Similarly, in the insecticide, fluopicolide comprises 20% and pymetrozine 30%, leading to a fluoride content of 1.66% (i.e., 16.6 mg/kg). Typical application rates for these chemicals are 180–250 mg/(mu∙season) for herbicides and 15–20 g/(mu∙season) for insecticides. Each year, the fluoride contribution from herbicides ranges from 4.54×10 − 6 -6.30×10 − 6 mg/(m²∙year); for insecticides, it is between 1.49×10 − 3 -1.99×10 − 3 mg/(m²∙year). Thus, the total annual fluoride input from the use of these fluoride-containing pesticides in the tea gardens is relatively minor, ranging from 1.49×10 − 3 -1.99×10 − 3 mg/(m²∙year), and is considered negligible. Consequently, pesticides do not constitute a significant source of fluoride in the surface soil of the tea gardens. 4. Conclusion The average total fluoride content in the soil of the typical brick tea planting area in Chibi ranges from 349 mg/kg to 946 mg/kg, with an average of 552 mg/kg. This is significantly higher than the average fluoride concentration in China's surface soil. The water-soluble fluoride content varies from 0.85 to 10.12 mg/kg, with an average of 2.66 mg/kg, constituting 0.15–1.41% of the total fluoride content. The region predominantly features red and yellow soils, with a pH range from 3.70 to 5.60, averaging 4.20, indicative of acidic conditions. Distribution pattern of fluoride in soil: The distribution of fluoride content in different types of surface soil in the tea gardens follows the sequence of red soils > young red soils > yellow-red soils. Overall, the surface soil fluoride content in this area exhibits a declining trend from north to south. Under acidic conditions, pH fluctuations have a minimal impact on the water-soluble fluoride content in the soil. Primary sources of fluoride in the soil: The geological stratum is a primary source of fluoride in the soil, with the parent material layer of the tea gardens showing high fluoride levels (above background values). The soil parent material is residual, formed by in situ weathering, where fluoride elements from the parent layer migrate and accumulate in the surface soil of the tea gardens. Additionally, the prolonged and extensive use of Yangfeng and Western compound fertilizers significantly contributes to elevated fluoride content in the soil. Atmospheric deposition, irrigation water, and pesticide application in the tea gardens have a minor impact on the fluoride levels in the surface soil. Declarations Funding This work was supported by the science and technology financial support from Xianning Science and Technology Bureau(Grant numbers[2021NYYF011]). Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Quan Li,Yang Li, Zhigang Li and Chen Yi. The first draft of the manuscript was written by Quan Li , review and editing was by Qian Wang, supervision was by Li Liu, resources are provided by Guoping Xia, . and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. References China National Environmental Monitoring Station. Background Values of Soil Elements in China [M]. Beijing: China Environmental Science Press, 1990... Li Xiaoliang, Chen Xiaomin, Zhou Lianchuan, et al. Fluoride Content in Soils of the Karst Desertification Area in Southwest China and Its Influencing Factors [J]. Journal of Safety and Environment, 2010, 10(02): 77-81... Yi Chunyao, Wang Bingguo, Jin Menggui. Forms and Distribution Characteristics of Fluorine in Soils of Typical Areas in the North China Plain [J]. Environmental Science, 2013, 34(08): 3195-3204... Xiang Jianqiao, Zhao Min, Yang Jun, et al. Handbook of Soil Geochemical Background Values in Hubeian Province [M]. China University of Geosciences Press, 2023: 1-309... CAMARENA-RANGEL N, ROJAS VELÁZQUEZ A N, SANTOS-DÍAZ M D S. Fluoride bioaccumulation by hydroponic cultures of camellia (Camellia japonica spp.) and sugar cane (Saccharum officinarum spp.)[J]. Chemosphere, 2015,136: 56-62... SHU W S, ZHANG Z Q, LAN C Y, et al. Fluoride and aluminium concentrations of tea plants and tea products from Sichuan Province, PR China[J]. Chemosphere, 2003,52(9): 1475-1482... Ruan J, Ma L, Shi Y, et al. Uptake of fluoride by tea plant (Camellia sinensis L) and the impact of aluminum[J]. Journal of the Science of Food and Agriculture, 2003, 83(13): 1342-1348... Weinstein L H, Davison A. Fluorides in the environment: effects on plants and animals[M]. Cabi, 2004... Moirana R L , Mkunda J , Perez M P ,et al.The influence of fertilizers on the behavior of fluoride fractions in the alkaline soil[J].Journal of Fluorine Chemistry, 2021, 250:109883-.DOI:10.1016/j.jfluchem.2021.109883... Gao H , Zhang Z , Wan X .Influences of charcoal and bamboo charcoal amendment on soil-fluoride fractions and bioaccumulation of fluoride in tea plants[J].Environmental Geochemistry & Health, 2012, 34(5):551-562.DOI:10.1007/s10653-012-9459-x... Gan C D , Jia Y B , Yang J Y .Remediation of fluoride contaminated soil with nano-hydroxyapatite amendment: Response of soil fluoride bioavailability and microbial communities[J].Journal of Hazardous Materials, 2021, 405:124694.DOI:10.1016/j.jhazmat.2020.124694... Wu Weihong, Xie Zhengmiao, Xu Jianming, Hong Ziping, Liu Chao. Characteristics and Influencing Factors of Fluorine Forms in Different Soils [J]. Environmental Science, 2002(02): 104-108... Hong P, Bang ben C, Ming F. DISCUSSION ON MECHANISM OF VARIATIONS IN CONTENT OF WATER-SOLUBLE FLUORINE DURING DESALINIZATION OF COASTAL SALINE SOILS OF JIANGSU PROVINCE [J]. Acta Pedologica Sinica, 1993, 4... Xie Z M, Wu W H, Xu J M. Translocation and transformation of fluorides in the environment and their biological effects[J]. Advances in Environmental Sciences, 1999, 7(2): 40-52... Xia Jingfen, Fu Jianbin, Luo Chunlin. Study on the Correlation between Water-soluble Fluorine, Total Fluorine, and pH Value in Tea Garden Soils [J]. Guangdong Trace Elements Science, 2009, 16(02): 41-45... Li Rongjuan. Detection of Fluoride Content in Border-Sold Tea and Characterization of the Sources and Distribution of Body Fluorine in Tea Trees [D]. Sichuan Agricultural University, 2013. Additional Declarations No competing interests reported. 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Hubei Geological Bureau","correspondingAuthor":true,"prefix":"","firstName":"Guoping","middleName":"","lastName":"Xia","suffix":""}],"badges":[],"createdAt":"2024-07-19 06:29:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4766502/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4766502/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":62938989,"identity":"accbd944-1f05-4ed1-82b3-0b23524eafcd","added_by":"auto","created_at":"2024-08-21 09:10:08","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":414770,"visible":true,"origin":"","legend":"\u003cp\u003eYiyang Bridge Tea Plantation \u0026nbsp;Sampling Plan\u003c/p\u003e","description":"","filename":"Fig.1YiyangBridgeTeaPlantationSamplingPlan.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/5372c96fa2b0cc42ae3be4b8.png"},{"id":62939749,"identity":"0c2061ce-b884-40cc-8e79-fa761f74eacd","added_by":"auto","created_at":"2024-08-21 09:18:08","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":498667,"visible":true,"origin":"","legend":"\u003cp\u003eBawang Temple Tea Plantation Sampling Plan\u003c/p\u003e","description":"","filename":"Fig.2BawangTempleTeaPlantationSamplingPlan.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/d5955edc8e38603bca1d8328.png"},{"id":62940290,"identity":"7afd113b-d600-44a9-a2f4-9c1007a00817","added_by":"auto","created_at":"2024-08-21 09:26:08","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":980984,"visible":true,"origin":"","legend":"\u003cp\u003eMap of Fluoride Levels in the Topsoilof Yiyang\u003c/p\u003e\n\u003cp\u003eBridge Tea Plantation and Surrounding Tea Plantations\u003c/p\u003e","description":"","filename":"Fig.3MapofFluorideLevelsintheTopsoilofYiyangBridgeTeaPlantationandSurroundingTeaPlantations.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/5c0153712dd5b34fe8d4d7f7.png"},{"id":62938988,"identity":"67eae382-c190-44ad-8b1d-f41d34555ddf","added_by":"auto","created_at":"2024-08-21 09:10:08","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":249052,"visible":true,"origin":"","legend":"\u003cp\u003eMap of Fluoride Levels in the Topsoil of Bawang \u0026nbsp;Temple Tea Plantation\u003c/p\u003e","description":"","filename":"Fig.4MapofFluorideLevelsintheTopsoilofBawangTempleTeaPlantation.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/c3169a11d4023c79ba291b78.png"},{"id":62938993,"identity":"3572ae24-ad09-4679-9489-c517e27dec70","added_by":"auto","created_at":"2024-08-21 09:10:08","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":155903,"visible":true,"origin":"","legend":"\u003cp\u003eChanges in the Fluoride Content in Vertical Soil Profiles\u003c/p\u003e","description":"","filename":"Fig.5ChangesintheFluorideContentinVerticalSoilProfiles.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/442feb9d63a0b6a0eae381a8.png"},{"id":62938991,"identity":"0dbd1df8-fd80-43e9-bf9a-55bb06cb7516","added_by":"auto","created_at":"2024-08-21 09:10:08","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":647009,"visible":true,"origin":"","legend":"\u003cp\u003ePhoto of Fertilizers in Chibi Tea Garden\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/a10c01a58170847510070881.png"},{"id":62939750,"identity":"a483fe06-f033-470e-ade1-56d0a5bf309c","added_by":"auto","created_at":"2024-08-21 09:18:08","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":335304,"visible":true,"origin":"","legend":"\u003cp\u003ePhoto of Herbicide Oxyfluorfen Phosphorus Ammonium (left), Insecticide Fluopicolide Pymetrozine (right)\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/0d0f2775f960a5d45e226334.png"},{"id":63183278,"identity":"adb5bece-c849-4ce8-809e-e9eeb4d84d36","added_by":"auto","created_at":"2024-08-24 11:49:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5801124,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/07206d7f-3b2a-490b-a829-ed4db1657456.pdf"},{"id":62939748,"identity":"8ec5c4b1-02b5-467e-ac75-ceea75831f0a","added_by":"auto","created_at":"2024-08-21 09:18:08","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":210648,"visible":true,"origin":"","legend":"","description":"","filename":"graphicalabstract.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4766502/v1/a4e687406053a311597ef3d1.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"Distribution Characteristics of Fluorine in the Soil of Brick Tea Plantations in Chibi and the Sources of Pollution","fulltext":[{"header":"Highlights","content":"\u003cul start=\"12\"\u003e\n \u003cli\u003eThe distribution of fluoride content follows the sequence of red soils \u0026gt; young red soils \u0026gt; yellow-red soils.\u003c/li\u003e\n \u003cli\u003epH fluctuations have a minimal impact on the water-soluble fluoride content in the soil\u0026nbsp;under acidic conditions.\u003c/li\u003e\n \u003cli\u003eThe geological stratum is a primary source of fluoride in the soil.\u003c/li\u003e\n \u003cli\u003eFertilizers significantly contributes to elevated fluoride content in the soil.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eThe average fluorine concentration in the surface soil of China stands at 453 mg/kg, ranging from 191\u0026ndash;1012 mg/kg, significantly exceeding the average global soil fluorine concentration of 200 mg/kg(China National Environmental Monitoring Station.1990). Research reveals a distinct regional pattern in China's soil fluorine content, with higher concentrations in the north compared to the south, vastly surpassing the global norm. The arid, scant rainfall conditions in the northwest region lead to minimal weathering and leaching, causing fluorine to be less mobile and thus maintaining higher soil fluorine levels. Conversely, in the southeastern coastal provinces, strong leaching coupled with high soil acidity facilitates the mobilization and leaching of fluorine, resulting in lower concentrations. The average fluorine content in the red soils of the southern regions is 65.6 mg/kg, while in the yellow and grey soils of the North China region, it averages 430.46 mg/kg (Li Xiaoliang et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Yi chunyao et al. 2013). Hubei Province's 2023 soil geochemical background data indicate an average fluorine content of 561 mg/kg in the surface soil of Chibi City(Xiang Jianqiao et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe primary regions for brick tea production in China are Hubei, Hunan, Sichuan, Yunnan, and Shaanxi. Studies indicate that tea plants (871\u0026ndash;2000 mg/kg) and camellias (1000\u0026ndash;1400 mg/kg) naturally accumulate high quantities of fluorine(CAMARENA-RANGEL N et al. 2015; SHU W S et al. 2003). Tea plants, in particular, are hyperaccumulators, containing 10\u0026ndash;100 times more fluorine than other plants in the same settings. The fluorine accumulation in tea plants is in direct proportion to environmental fluorine concentration(Ruan J et al. 2023), and the fluorine in tea predominantly originates from the soil. Factors such as soil pH, along with other cations and anions, influence fluorine absorption by plants. When the soil pH is between 5.5 and 6.5, plant uptake of soil fluorine is minimal(Weinstein L H et al. 2004).\u003c/p\u003e \u003cp\u003eThe bioavailability of fluorine in soil is determined by its chemical forms rather than its total content(Moirana R L et al. 2021). Fluorine exists in various forms in the soil, such as water-soluble, exchangeable, iron-manganese bound, organically bound, and residual(Gao H et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The distribution of fluorine content in different soil layers typically follows the order: residual\u0026thinsp;\u0026gt;\u0026thinsp;exchangeable\u0026thinsp;\u0026gt;\u0026thinsp;water-soluble\u0026thinsp;\u0026gt;\u0026thinsp;organic\u0026thinsp;\u0026gt;\u0026thinsp;amorphous iron oxide(Gan C D et al. 2020). Residual fluorine, which makes up over 90% of the total fluorine content, is the predominant form found in the soils of tea gardens. Water-soluble fluorine represents only 0.03%-0.44% of the total fluorine content. Both water-soluble and total fluorine levels in tea garden soils tend to decrease with increasing depth(Wu Weihong et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Additionally, water-soluble and exchangeable fluorine are readily available to plants, animals, microbes, and humans, being easily absorbed by crop roots and subsequently entering the food chain(Hong P et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1993\u003c/span\u003e; Xie Z M et al. 1999). The presence of water-soluble fluorine in soil is influenced by factors such as organic matter, parent material, soil texture, pH, and climatic conditions. Notably, groundwater pH significantly affects water-soluble fluorine levels; within a pH range of 6.0-8.5, each incremental increase of 0.5 in soil pH can raise the water-soluble fluorine content by 0.4\u0026ndash;0.5 mg/kg(Xia Jingfen et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). There is a positive correlation between the exchangeable and water-soluble fluorine in the soul and the total amount of cation exchange and organic matter in the soil.\u003c/p\u003e \u003cp\u003eGiven the high fluorine content in Chibi brick tea and the lack of comprehensive research on the distribution and sources of fluorine in this region's soil, this project employs specialized methods such as 1:10,000 hydrogeological, ecological environment geological surveys, atmospheric deposition monitoring, soil geochemical measurements, and vertical soil profile analysis. Samples of typical surface soil, different types of soil, fertilizers, and water quality from the Chibi brick tea planting areas are collected and tested to explore the correlations between key indicators. This study aims to characterize the distribution and identify the pollution sources of fluorine in the typical brick tea planting soils of Chibi, as well as assess the risk to the environmental quality of the surface soil in these tea gardens.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003ch2\u003e\u003cem\u003e2\u003c/em\u003e\u003cem\u003e.1\u003c/em\u003e\u003cem\u003e.\u003c/em\u003e\u003cem\u003e\u0026nbsp;Soil Sample Collection \u0026nbsp;\u003c/em\u003e\u003c/h2\u003e\n\u003cp\u003eThe layout and sampling methods for the project sites adhere to the \u0026quot;Specifications for Geochemical Evaluation of Land Quality\u0026quot; (DZ/T0295-2016). A total of 37 soil parent rock samples were collected, each weighing between 2.0-3.0 kg. The sampling density for surface soil samples was set at 50 points/km\u0026sup2;, resulting in 260 samples collected, each weighing between 1.0 kg and 1.5 kg, at a sampling depth of 0-20 cm. The sampling density for soil form samples was approximately 7 points/km\u0026sup2;, with 30 samples collected, each also weighing 1.0 kg-1.5 kg, at the same sampling depth. Soil vertical profiles were established based on different soil types, totaling 4 profiles. The profile depth ranged from 1.5-2.0 m, with 4 samples systematically collected from top to bottom at each profile location according to the distinct soil horizons, totaling 16 samples. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor the 36km\u003csup\u003e2\u003c/sup\u003e survey area, water quality samples were sourced from ponds, reservoirs, and wells, with a sampling density of approximately 1 point/2km\u003csup\u003e2\u003c/sup\u003e, resulting in 20 samples, each with a volume of 3-5 L. The sampling density for atmospheric dry and wet deposition was set at 1 point/12km\u003csup\u003e2\u003c/sup\u003e, with 3 atmospheric deposition monitoring stations established, and samples collected semi-annually, including 6 samples each of atmospheric dust and precipitation. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe sampling locations are depicted in Figures 1 and 2.\u003c/p\u003e\n\u003ch2\u003e2.2. Experimental Instruments \u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eInstruments include a PXSL-216F type ion meter, Leici PHSJ-4A pH meter, a balance, soil nutrient tester, mortar, Muffle furnace, and a reciprocating horizontal oscillating bed.\u003c/p\u003e\n\u003ch2\u003e2.3. Sample Analysis Methods \u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eTotal fluorine content in the soil is determined according to GB/T 22104-2008 \u0026quot;Soil Quality - Determination of Fluoride with Ion-selective Electrodes\u0026quot;. Soil pH is measured using a potentiometric method with a soil to water ratio of 2.5:1. Soil ammonium nitrogen, available potassium, available phosphorus, and organic matter are quantified using the Ruilong brand soil nutrient tester. Various forms of fluorine in the soil are extracted and quantified through the Tessier five-step sequential leaching method. The leaching toxicity of soil fluorine is assessed based on the \u0026quot;Solid Waste - Leaching Toxicity Sulphuric Acid \u0026amp; Nitric Acid Method.\u0026quot;\u003c/p\u003e\n\u003ch2\u003e2.4. Data Processing \u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eData analysis is performed using Excel 2016, Origin2017 mapping software, and SPSS statistical software for correlation analysis.\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Geochemical Characteristics of Soil Fluorine and Influencing Factors\u003c/h2\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1 Influence of Soil Parent Rock Material on Soil Fluorine Content\u003c/h2\u003e\n \u003cp\u003eThe type of parent rock material plays a crucial role in determining the total fluorine content in soil. The parent rock, which is the original rock from which the soil is derived, influences the soil\u0026apos;s chemical properties through its chemical and mineral compositions, thereby significantly affecting the fluorine content(Hong P et al. \u003cspan class=\"CitationRef\"\u003e1993\u003c/span\u003e). Survey results indicate that the fluorine content in the silty claystone of the Shipai Formation is substantially higher than in silty shale, likely due to differences in mineral composition. Clay minerals are known for their strong adsorption capacity, enabling them to bind fluoride ions in the soil. Additionally, the layered structure of these minerals provides numerous adsorption sites for fluoride ions, thereby increasing the soil\u0026apos;s fluorine concentration. Conversely, dolomite and limestone, primarily composed of calcium carbonate and magnesium-containing minerals, respectively, exhibit weaker adsorption capacities for fluoride ions, which results in lower fluorine content in these soils. The fluorine content of the various rocks is detailed in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eAccording to the data in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, the average fluorine content in surface soils of different types in the region\u0026apos;s tea gardens ranks as follows: brown red soil\u0026thinsp;\u0026gt;\u0026thinsp;young red soil\u0026thinsp;\u0026gt;\u0026thinsp;yellow red soil, as illustrated in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eThe formation process of brown red soil involves organic matter accumulation, clayification, desilication, and alumination. Consequently, the brown red soil in Chibi tea gardens is rich in Al\u003csup\u003e3+\u003c/sup\u003e, which readily reacts with F\u003csup\u003e-\u003c/sup\u003e to form aluminum fluoride complexes. This reaction enhances the soil\u0026apos;s capacity to adsorb fluorine, thereby increasing its fluorine content.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSoil Fluorine Content in Different Parent Rocks\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample ID\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGeological Background\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRock Type\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003cp\u003emg/kg\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNo.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample ID\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGeological Background\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRock Type\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003cp\u003emg/kg\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e829\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e819\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e694\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e816\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e745\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e812\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e742\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e900\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e696\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e922\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e736\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e742\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e745\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e879\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e227\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e628\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e230\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e611\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e151\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e664\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e169\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e708\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e191\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e733\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e713\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e190\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXintan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e763\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e33\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e157\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBaota Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLimestone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eShipai Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSiltstone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e190\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLoushanguan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDolomite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLongmaxi Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e787\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLoushanguan Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDolomite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLongmaxi Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e793\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCJK-37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLongmaxi Formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSilty claystone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e641\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSoil Fluorine Content in Different Parent Materials\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSoil Type\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eUnit\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBrown Red Soil\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eYellow Red Soil\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eYoung Red Soil\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSample Quantity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003epcs\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e113\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMinimum Value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003emg/kg\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e408\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e349\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e502\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaximum Value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003emg/kg\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e946\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e742\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e718\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage Value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003emg/kg\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e574\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e529\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e566\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eArea\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003emu\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e339226\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e225150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e36024\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eArea Proportion\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e56.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2 Correlation Analysis of Soil Water-Soluble Fluorine Content and Total Fluorine Content\u003c/h2\u003e\n \u003cp\u003eIn this study, 30 surface soil samples from 0\u0026ndash;20 cm depth in tea gardens were analyzed for both water-soluble and total fluorine content. The soil fluorine content in the tea gardens ranged from 349\u0026ndash;946 mg/kg, with an average of 552 mg/kg. The water-soluble fluorine content varied from 0.85 to 10.12 mg/kg, averaging 2.66 mg/kg, which represents 0.15\u0026ndash;1.41% of the total fluorine content, as shown in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. A correlation analysis conducted using SPSS software yielded a correlation coefficient (r) of 0.41 and p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 with n\u0026thinsp;=\u0026thinsp;30, indicating a modest positive correlation between the water-soluble and total fluorine content.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSoil Sample Test Results\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample ID\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWater-Soluble Fluorine (mg/kg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal Fluorine (mg/kg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWater-Soluble Fluorine/Total Fluorine (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSample ID\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWater-Soluble Fluorine (mg/kg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal Fluorine (mg/kg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWater-Soluble Fluorine/Total Fluorine (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e494.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e594.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.95\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e795.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e777.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e553.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e702.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.92\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e501.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.67\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e696.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.16\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e551.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e685.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.28\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e535.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e598.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.65\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e544.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-22\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e580.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.09\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e581.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e742.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.88\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e565.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e650.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e590.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e376.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e573.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e420.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.39\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e718.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e676.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.77\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e587.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.91\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e463.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e652.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e526.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.73\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e945.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCBXT-30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e551.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.87\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.3 The Influence of Soil pH on the Forms of Water-Soluble Fluoride in Soil\u003c/h2\u003e\n \u003cp\u003eIn this study, 30 samples of 0\u0026ndash;20 cm surface soil from the tea gardens were collected. The soil pH ranged from 3.70 to 5.60, with an average value of 4.20. A correlation analysis between the water-soluble fluoride content and soil pH in these soils revealed that within the pH range of 3.70\u0026ndash;3.95, no significant correlation was observed between water-soluble fluoride content and soil pH (r\u0026thinsp;=\u0026thinsp;0.09, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05, n\u0026thinsp;=\u0026thinsp;9). However, within the pH range of 4.02\u0026ndash;5.60, a weak positive correlation was found (r\u0026thinsp;=\u0026thinsp;0.20, P\u0026thinsp;\u0026gt;\u0026thinsp;0.05, n\u0026thinsp;=\u0026thinsp;21). This weak correlation may be due to competitive adsorption between hydroxide (OH-) and fluoride (F-) ions on clay minerals, which have similar ionic radii. As soil pH decreases, the release of OH- increases, thereby enhancing the soil\u0026rsquo;s ability to adsorb fluoride and reducing the content of water-soluble fluoride.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Distribution Patterns of Fluoride in the Soil of Tea Fields\u003c/h2\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1 Horizontal Distribution Patterns\u003c/h2\u003e\n \u003cp\u003eUtilizing software for the management and maintenance of geochemical survey data and land quality assessment, fluoride content values were assigned to each evaluation unit within the tea garden areas. Adhering to the \u0026quot;Geochemical Evaluation Standards for Land Quality\u0026quot; (DZ/T0295-2016), the soil fluoride levels in each evaluation unit were categorized as per the classifications detailed in Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. The soil fluoride categorization results in the tea gardens are depicted in Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. Regarding spatial distribution, there is a general trend of decreasing surface soil fluoride content from north to south, as illustrated in Figs. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e and 4.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eSoil Fluorine Classification\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eIndex Range\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u0026gt;700\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e550\u0026ndash;700\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e500\u0026ndash;550\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e400\u0026ndash;500\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u0026le;\u0026thinsp;400\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eIndex Level\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFirst Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSecond Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThird Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFourth Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFifth Level\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAbundance-Deficiency Level\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExtremely Abundant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbundant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMarginal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLacking\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\"\u003eNote: The grading standards are based on the \u0026quot;Specifications for Geochemical Evaluation of Land Quality\u0026quot; (DZ/T0295-2016).\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eFluoride Level Classification Results in Tea Garden Soil\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNumber\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eIndex Range\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eIndex Level\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAbundance-Deficiency Level\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eExceedance Level\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eArea (mu)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePercentage (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFirst Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExtremely abundant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot exceeding standard\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e550\u0026ndash;700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSecond Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbundant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot exceeding standard\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2290\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e500\u0026ndash;550\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eThird Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eModerate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot exceeding standard\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2027\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.76\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e400\u0026ndash;500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFourth Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMarginal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot exceeding standard\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1571\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026le;\u0026thinsp;400\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFifth Level\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLacking\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot exceeding standard\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.32\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2 Vertical Distribution Patterns\u003c/h2\u003e\n \u003cp\u003eSoil vertical profiles are organized according to different soil types, with a total of four profiles, labeled CBCP-01 to CBCP-4, with depths ranging from 1.5 to 2.0 meters. At each profile location, four soil samples are sequentially collected from the top downward, each representing a distinct soil horizon.\u003c/p\u003e\n \u003cp\u003eAs depicted in Fig. 5, the topsoil layer (0-20cm) and the deep subsoil layer (below 140cm) exhibit higher fluoride content. The intermediate soil layer (20-140cm) shows relatively lower fluoride content. This pattern can be attributed to several factors: the topsoil experiences secondary fluoride enrichment and receives additional fluoride from fertilizers, leading to elevated levels; fluoride migration from the deeper layers to the topsoil, combined with the long-term absorption of fluoride by tea tree roots, results in diminished fluoride levels in the intermediate layers; and the naturally high fluoride content in the parent material of the tea garden, which dissolves and migrates to the deeper soil layers during soil formation, contributes to the higher fluoride levels observed in these areas.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Analysis of the Material Sources of Soil Fluoride\u003c/h2\u003e\n \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e\n \u003ch2\u003e3.3.1 Characteristics of Fluoride Changes from Atmospheric Deposition\u003c/h2\u003e\n \u003cp\u003eFluoride in the atmosphere primarily exists as aerosols, which diffuse and mix thoroughly with various atmospheric components. Atmospheric fluoride then settles on the earth\u0026apos;s surface or is washed down by rainfall, integrating into the soil.\u003c/p\u003e\n \u003cdiv id=\"Sec17\" class=\"Section4\"\u003e\n \u003ch2\u003e3.3.1.1 Atmospheric Dry Deposition\u003c/h2\u003e\n \u003cp\u003eIn the first evaluation area, Yiyang Bridge Tea Plantation and its surroundings, atmospheric dry and wet deposition monitoring stations were established on August 21, 2022 and March 17, 2023 (CBDQ-01, CBDQ-02), with biannual sampling resulting in four collections. In the second evaluation area, Bawang Temple Tea Plantation, a monitoring station (CBDQ-03) was set up on March 17, 2023, with biannual sampling amounting to two collections. The analysis of the elemental content in atmospheric dust is detailed in Table \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e, while the characteristics of these elements in the two evaluation areas are presented in Tables \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab6\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAnalysis of Element Content Characteristics in Atmospheric Dust at Monitoring Points #1 and #2\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eCBDQ-01(1#)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eCBDQ-02(2#)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSoil Average\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSoil Average\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.42\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.38\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e276\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e55.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e165.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e112.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e24.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e112.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e273\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e129\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e201.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e69.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e44.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.29\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e646\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e292\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e469.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e552\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e116\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e552\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"11\"\u003eNote: Content unit mg/kg, K\u0026thinsp;=\u0026thinsp;average value of atmospheric dust elements in the evaluation area/average value of soil elements in the evaluation area\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab7\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAnalysis of Element Content Characteristics in Atmospheric Dust in Evaluation Area One\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSoil Average\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.58\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e276\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e90.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e112.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e29.20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e273\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e122.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.57\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e646\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e552\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\"\u003eNote: Content unit mg/kg, K\u0026thinsp;=\u0026thinsp;average value of atmospheric dust elements in the evaluation area/average value of soil elements in the evaluation area\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab8\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAnalysis of Element Content Characteristics in Atmospheric Dust in Evaluation Area Two\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSoil Average\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.49\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e20.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.097\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.62\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e26.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.87\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e112.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e62.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e152\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e552\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\"\u003eNote: Content unit mg/kg, K\u0026thinsp;=\u0026thinsp;average value of atmospheric dust elements in the evaluation area/average value of soil elements in the evaluation area\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec18\" class=\"Section4\"\u003e\n \u003ch2\u003e3.3.1.2 Atmospheric Wet Deposition\u003c/h2\u003e\n \u003cp\u003eAtmospheric precipitation samples are collected concurrently with atmospheric dust samples. Rainfall, a crucial aspect of atmospheric deposition, undergoes complex chemical reactions as it descends from the clouds to the ground. These reactions are influenced by both natural and anthropogenic chemicals in the atmosphere, altering the chemical composition of the rainwater and facilitating the migration and dispersion of heavy metals. Consequently, rainfall serves as a primary mediator of the geochemical cycle of materials.\u003c/p\u003e\n \u003cp\u003eThe analysis of heavy metal pollutants and pH values for 2021\u0026ndash;2023 in the evaluation area is presented in Table \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e. Notably, at monitoring point CBDQ-01 (1#), the minimum pH recorded is 3.18, which falls below the standards set in the \u0026apos;Environmental Technical Conditions for Tea Production Areas (NYT 853\u0026ndash;2004)\u0026apos;. However, the levels of As, Hg, Cr, Cd, Pb, and F elements within the evaluation area comply with the NYT 853\u0026ndash;2004 standards. This pH discrepancy is suspected to be caused by emissions from nearby tea processing factories, which release sulfur dioxide from coal combustion, subsequently dissolving into the rainwater and reducing its pH value.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab9\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAnalysis of the Main Element Content in Atmospheric Precipitation at Each Monitoring Point in the Evaluation Area\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eCBDQ-01(1#)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eCBDQ-01(2#)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eCBDQ-01(3#)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eStandard value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.88\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.37\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.36\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNot detected\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e100.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.243\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.127\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.078\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.103\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.159\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.115\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.5\u0026ndash;7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"11\"\u003eNote: As-Pb content unit is \u0026micro;g/L, F- content unit is mg/L, pH is dimensionless. Standard values refer to \u0026apos;Environmental Technical Conditions for Tea Production Areas (NYT 853\u0026ndash;2004)\u0026apos;\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec19\" class=\"Section4\"\u003e\n \u003ch2\u003e3.3.1.3 Classification\u003c/h2\u003e\n \u003cp\u003eThe sum of the annual flux of atmospheric dry and wet deposition is calculated by adding together the fluxes from the first and second halves of the year. These details are depicted in Tables \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eAccording to the \u0026apos;Standards for Geochemical Evaluation of Land Quality\u0026apos; (DZ/T0295-2016), classification indices for atmospheric dry and wet deposition fluxes focus on the indicators for Cd and Hg. Division standard values are provided in Table \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab10\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 10\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAtmospheric Dry and Wet Deposition Flux Table for Evaluation Area One\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eSix-month deposition flux (mg\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAnnual flux\u003c/p\u003e\n \u003cp\u003e(mg\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eFirst half of the year\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eSecond half of the year\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDry\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWet\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDry\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWet\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1736\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1328\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0934\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1615\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5613\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0031\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0099\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0153\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.2899\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1755\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.2279\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.2912\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.9845\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1210\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0248\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0176\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0423\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.2057\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.4969\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0274\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.2196\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3484\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.0923\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.4149\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25.9053\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.8686\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.5876\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e53.7764\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab11\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 11\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAtmospheric Dry and Wet Deposition Flux Table for Evaluation Area Two\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003eElement\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eSix-month deposition flux (mg\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAnnual flux\u003c/p\u003e\n \u003cp\u003e(mg\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eFirst half of the year\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eSecond half of the year\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDry\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWet\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDry\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWet\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.5259\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.4319\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0208\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.2326\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.2112\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0113\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0449\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0562\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.1137\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.2292\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0136\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.6065\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.9630\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3265\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0316\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3592\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.2652\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0309\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.2493\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.5454\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.7258\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e35.6356\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e85.4186\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e138.78\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab12\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 12\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eStandard Values for Environmental Geochemical Grades of Atmospheric Dry and Wet Deposition Flux\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEvaluation Indicator\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eAnnual flux(mg∙m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e∙a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLevel\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFirst Level, digital code is 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSecond Level, digital code is 2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026le;\u0026thinsp;3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026le;\u0026thinsp;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eReferring to Table \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e, the annual atmospheric dry and wet deposition flux of Cd in evaluation area one amounts to 0.2057 mg/(m\u0026sup2;∙a), and Hg to 0.0153 mg/(m\u0026sup2;∙a), both significantly below the level 1 grade standard values. The pH values of atmospheric precipitation in this area range from 3.18 to 7.75, typically acidic. The Cd and Hg environmental geochemical levels and overall grades of atmospheric dry and wet deposition flux in this area are categorized as grade 1.\u003c/p\u003e\n \u003cp\u003eSimilarly, the annual atmospheric dry and wet deposition flux of Cd in evaluation area two is 0.3592 mg/(m\u0026sup2;∙a), and Hg is 0.0562 mg/(m\u0026sup2;∙a), also considerably below the level 1 grade standard values. The pH values of atmospheric precipitation here range between 6.62 and 7.60. The Cd and Hg environmental geochemical levels and overall grades of atmospheric dry and wet deposition flux in this area are also classified as grade 1.\u003c/p\u003e\n \u003cp\u003eThe daily average values of atmospheric fluoride in both areas are 1.47 \u0026micro;g/(dm\u0026sup2;∙d) and 3.80 \u0026micro;g/(dm\u0026sup2;∙d), respectively, adhering to the \u0026apos;Environmental Technical Conditions for Tea Production Areas\u0026apos; (NYT 853\u0026ndash;2004) standard of 5.0 \u0026micro;g/(dm\u0026sup2;∙d), indicating that atmospheric deposition does not contribute to the fluoride content in the topsoil of the tea gardens.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Characteristics of Fluoride Variation in Irrigation Water\u003c/h2\u003e\n \u003cp\u003eWater plays a pivotal role as the principal driving force and carrier of fluoride transfer in soil. During the survey, 20 irrigation water samples were collected from reservoirs, ponds, and wells near the tea gardens. These samples underwent analyses for pH, fluoride, and heavy metal content, with the results detailed in the following table. Notably, the highest recorded mercury content was 0.008 mg/L, which surpasses the limit set by the \u0026apos;Environmental Technical Conditions for Tea Production Areas\u0026apos; (NYT 853\u0026ndash;2005) by sevenfold. Out of the samples, four exceeded this mercury threshold, representing a 20% exceedance rate; the highest cadmium content reached 0.04027 mg/L, also exceeding the NYT 853\u0026ndash;2004 standard by seven times, with eight samples also exceeding the cadmium threshold, resulting in a 40% exceedance rate; pH levels ranged from 6.86 to 8.76, with five samples surpassing the NYT 853\u0026ndash;2004 threshold, an exceedance rate of 25%. However, the content of fluoride and heavy metals such as arsenic, lead, and chromium all complied with the NYT 853\u0026ndash;2004 standards, indicating that irrigation water is not a significant source of fluoride in the topsoil of the tea gardens.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab13\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 13\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eStatistical Table of Test Results for Tea Garden Irrigation Water Samples (unit: mg/L)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAnalysis item\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMinimum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaximum\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStandard value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0150\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0022\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00007\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00106\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.04027\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00574\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.00500\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0117\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0019\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr6+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.100\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.075\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.163\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003epH (dimensionless)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.5\u0026ndash;7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003eNote: Standard values refer to \u0026apos;Environmental Technical Conditions for Tea Production Areas\u0026apos; (NYT 853\u0026ndash;2004).\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Characteristics of Fluoride in Fertilizers\u003c/h2\u003e\n \u003cp\u003eFertilizers are extensively used in agricultural settings to enhance crop yields. However, the impact of fertilizers on fluoride ions in soil is not well-understood. Fluoride ions are absorbed and transported through dissolution into soil, interactions with soil salts, and contact with root exudates. Fertilizer application modifies soil properties, making the study of fluoride ion bioavailability in soil crucial. Research by R.L. Moirana et al. indicates that the application of urea, diammonium phosphate, and organic fertilizers significantly increases the concentration of water-soluble fluoride (Ws-F) in the soil, while the levels of exchangeable fluoride (Ex-F) and fluoride associated with iron/manganese (Fe/Mn-F) remain relatively unchanged(Moirana R L et al. 2021). Thus, fertilizers primarily influence the concentration of water-soluble fluoride in the soil. Further research by Li Rongjuan in 2011 noted that the primary tea varieties in Sichuan\u0026mdash;Fuzhuan, Kangzhuan, and Jinjian\u0026mdash;had average fluoride contents of 989 mg/kg, 765 mg/kg, and 856 mg/kg, respectively, significantly exceeding the 300 mg/kg limit set by the \u0026apos;Fluoride Content in Brick Tea\u0026apos; (GB 19965\u0026thinsp;\u0026minus;\u0026thinsp;2005)(Li Rongjuan 2013). In that year, the primary fertilizers used in Sichuan tea gardens included ammonium bicarbonate, urea, ammonium nitrate, ammonium sulfate, potassium sulfate, and potassium nitrate, with fluoride contents ranging from 22,500 to 45,600 mg/kg. The high fluoride levels in these chemical fertilizers have contributed to the high fluoride content in the surface soil of tea gardens.\u003c/p\u003e\n \u003cp\u003eThe Chibi ten-thousand-mu tea garden predominantly utilizes Yangfeng and Western compound fertilizers, along with organic fertilizers. Typical application rates are 50\u0026ndash;100 kg/(mu∙season) for compound fertilizers and 100\u0026ndash;300 kg/(mu∙season) for organic fertilizers. This project analyzed four samples of compound fertilizers and two samples of organic fertilizers, finding that their pH values and the levels of cadmium, mercury, arsenic, lead, and chromium all comply with the \u0026apos;Limits of Harmful Substances in Fertilizers\u0026apos; (GB38400-2019), as presented in Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eCompared to organic fertilizers, compound fertilizers contain significantly higher fluoride levels, ranging from 8,600 to 13,300 mg/kg, with an average of 10,950 mg/kg\u0026mdash;nearly 20 times the average soil fluoride content of 349\u0026ndash;946 mg/kg. The annual fluoride contribution from using Yangfeng and Western compound fertilizers in the tea gardens amounts to 2,579-7,976 mg/(m\u0026sup2;∙year), with an average of 5,278 mg/(m\u0026sup2;∙year). Given these findings, it is advisable for tea gardens to increase their use of organic and nitrogen-based fertilizers and decrease their reliance on compound fertilizers to reduce the fluoride levels in brick tea.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab14\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 14\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eTest Results of Tea Garden Fertilizers (unit: mg/kg)\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eItem\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"5\"\u003e\n \u003cp\u003eCompound Fertilizer\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eOrganic Fertilizer\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCBFL-01\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCBFL-02\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCBFL-03\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCBFL-04\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStandard value\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCBFL-05\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCBFL-06\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eStandard value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.5\u0026ndash;8.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.5\u0026ndash;8.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e33.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.053\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.074\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e410\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"9\"\u003eNote: Standard values refer to \u0026apos;Limits of Harmful Substances in Fertilizers\u0026apos; (GB38400-2019).\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 Characteristics of Fluoride in Pesticides\u003c/h2\u003e\n \u003cp\u003eIn the Chibi ten-thousand-mu tea garden, the main fluoride-containing pesticides utilized include the herbicide oxyfluorfen phosphorus ammonium and the insecticide fluopicolide pymetrozine. The active components in the herbicide are phosphorus ammonium at 24% and ethoxyfluorfen at 8%, resulting in a fluoride content of 0.42% (i.e., 4.2 mg/kg). Similarly, in the insecticide, fluopicolide comprises 20% and pymetrozine 30%, leading to a fluoride content of 1.66% (i.e., 16.6 mg/kg). Typical application rates for these chemicals are 180\u0026ndash;250 mg/(mu∙season) for herbicides and 15\u0026ndash;20 g/(mu∙season) for insecticides.\u003c/p\u003e\n \u003cp\u003eEach year, the fluoride contribution from herbicides ranges from 4.54\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e-6.30\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;6\u003c/sup\u003e mg/(m\u0026sup2;∙year); for insecticides, it is between 1.49\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e-1.99\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e mg/(m\u0026sup2;∙year). Thus, the total annual fluoride input from the use of these fluoride-containing pesticides in the tea gardens is relatively minor, ranging from 1.49\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e-1.99\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e mg/(m\u0026sup2;∙year), and is considered negligible. Consequently, pesticides do not constitute a significant source of fluoride in the surface soil of the tea gardens.\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThe average total fluoride content in the soil of the typical brick tea planting area in Chibi ranges from 349 mg/kg to 946 mg/kg, with an average of 552 mg/kg. This is significantly higher than the average fluoride concentration in China's surface soil. The water-soluble fluoride content varies from 0.85 to 10.12 mg/kg, with an average of 2.66 mg/kg, constituting 0.15\u0026ndash;1.41% of the total fluoride content. The region predominantly features red and yellow soils, with a pH range from 3.70 to 5.60, averaging 4.20, indicative of acidic conditions.\u003c/p\u003e \u003cp\u003eDistribution pattern of fluoride in soil: The distribution of fluoride content in different types of surface soil in the tea gardens follows the sequence of red soils\u0026thinsp;\u0026gt;\u0026thinsp;young red soils\u0026thinsp;\u0026gt;\u0026thinsp;yellow-red soils. Overall, the surface soil fluoride content in this area exhibits a declining trend from north to south. Under acidic conditions, pH fluctuations have a minimal impact on the water-soluble fluoride content in the soil.\u003c/p\u003e \u003cp\u003ePrimary sources of fluoride in the soil: The geological stratum is a primary source of fluoride in the soil, with the parent material layer of the tea gardens showing high fluoride levels (above background values). The soil parent material is residual, formed by in situ weathering, where fluoride elements from the parent layer migrate and accumulate in the surface soil of the tea gardens. Additionally, the prolonged and extensive use of Yangfeng and Western compound fertilizers significantly contributes to elevated fluoride content in the soil. Atmospheric deposition, irrigation water, and pesticide application in the tea gardens have a minor impact on the fluoride levels in the surface soil.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the science and technology\u0026nbsp;financial support\u0026nbsp;from\u0026nbsp;Xianning Science and Technology Bureau(Grant numbers[2021NYYF011]).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Quan Li,Yang Li, Zhigang Li and Chen Yi. The first draft of the manuscript was written by Quan Li , review and editing was by Qian Wang, supervision was by Li Liu, resources are provided by Guoping Xia, . and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eChina National Environmental Monitoring Station. Background Values of Soil Elements in China [M]. Beijing: China Environmental Science Press, 1990...\u003c/li\u003e\n \u003cli\u003eLi Xiaoliang, Chen Xiaomin, Zhou Lianchuan, et al. Fluoride Content in Soils of the Karst Desertification Area in Southwest China and Its Influencing Factors [J]. Journal of Safety and Environment, 2010, 10(02): 77-81...\u003c/li\u003e\n \u003cli\u003eYi Chunyao, Wang Bingguo, Jin Menggui. Forms and Distribution Characteristics of Fluorine in Soils of Typical Areas in the North China Plain [J]. Environmental Science, 2013, 34(08): 3195-3204...\u003c/li\u003e\n \u003cli\u003eXiang Jianqiao, Zhao Min, Yang Jun, et al. Handbook of Soil Geochemical Background Values in Hubeian Province [M]. China University of Geosciences Press, 2023: 1-309...\u003c/li\u003e\n \u003cli\u003eCAMARENA-RANGEL N, ROJAS VEL\u0026Aacute;ZQUEZ A N, SANTOS-D\u0026Iacute;AZ M D S. Fluoride bioaccumulation by hydroponic cultures of camellia (Camellia japonica spp.) and sugar cane (Saccharum officinarum spp.)[J]. Chemosphere, 2015,136: 56-62...\u003c/li\u003e\n \u003cli\u003eSHU W S, ZHANG Z Q, LAN C Y, et al. Fluoride and aluminium concentrations of tea plants and tea products from Sichuan Province, PR China[J]. Chemosphere, 2003,52(9): 1475-1482...\u003c/li\u003e\n \u003cli\u003eRuan J, Ma L, Shi Y, et al. Uptake of fluoride by tea plant (Camellia sinensis L) and the impact of aluminum[J]. Journal of the Science of Food and Agriculture, 2003, 83(13): 1342-1348...\u003c/li\u003e\n \u003cli\u003eWeinstein L H, Davison A. Fluorides in the environment: effects on plants and animals[M]. Cabi, 2004...\u003c/li\u003e\n \u003cli\u003eMoirana R L , Mkunda J , Perez M P ,et al.The influence of fertilizers on the behavior of fluoride fractions in the alkaline soil[J].Journal of Fluorine Chemistry, 2021, 250:109883-.DOI:10.1016/j.jfluchem.2021.109883...\u003c/li\u003e\n \u003cli\u003eGao H , Zhang Z , Wan X .Influences of charcoal and bamboo charcoal amendment on soil-fluoride fractions and bioaccumulation of fluoride in tea plants[J].Environmental Geochemistry \u0026amp; Health, 2012, 34(5):551-562.DOI:10.1007/s10653-012-9459-x...\u003c/li\u003e\n \u003cli\u003eGan C D , Jia Y B , Yang J Y .Remediation of fluoride contaminated soil with nano-hydroxyapatite amendment: Response of soil fluoride bioavailability and microbial communities[J].Journal of Hazardous Materials, 2021, 405:124694.DOI:10.1016/j.jhazmat.2020.124694...\u003c/li\u003e\n \u003cli\u003eWu Weihong, Xie Zhengmiao, Xu Jianming, Hong Ziping, Liu Chao. Characteristics and Influencing Factors of Fluorine Forms in Different Soils [J]. Environmental Science, 2002(02): 104-108...\u003c/li\u003e\n \u003cli\u003eHong P, Bang ben C, Ming F. DISCUSSION ON MECHANISM OF VARIATIONS IN CONTENT OF WATER-SOLUBLE FLUORINE DURING DESALINIZATION OF COASTAL SALINE SOILS OF JIANGSU PROVINCE [J]. Acta Pedologica Sinica, 1993, 4...\u003c/li\u003e\n \u003cli\u003eXie Z M, Wu W H, Xu J M. Translocation and transformation of fluorides in the environment and their biological effects[J]. Advances in Environmental Sciences, 1999, 7(2): 40-52...\u003c/li\u003e\n \u003cli\u003eXia Jingfen, Fu Jianbin, Luo Chunlin. Study on the Correlation between Water-soluble Fluorine, Total Fluorine, and pH Value in Tea Garden Soils [J]. Guangdong Trace Elements Science, 2009, 16(02): 41-45...\u003c/li\u003e\n \u003cli\u003eLi Rongjuan. Detection of Fluoride Content in Border-Sold Tea and Characterization of the Sources and Distribution of Body Fluorine in Tea Trees [D]. Sichuan Agricultural University, 2013.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Soil, Brick Tea, Fluorine, Geological Strata, Compound Fertilizer","lastPublishedDoi":"10.21203/rs.3.rs-4766502/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4766502/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTea plants are known hyperaccumulators of fluorine and accumulate quantities of fluorine proportional to the concentration of fluorine in the environment. The primary source of fluorine in tea is water-soluble fluorine compounds in the soil, which tea plants readily absorb and accumulate in the leaves. Analyses of soil samples indicate that the parent material of soil significantly influences the total fluorine content. The distribution of fluorine in the surface soil of different soil types within the tea gardens follows this order: brown red soil \u0026gt; young red soil \u0026gt; yellow red soil. Generally, fluorine content in the surface soil of the planting area displays a decreasing trend from north to south. Under acidic conditions, pH variations minimally impact the concentration of water-soluble fluorine in the soil. Exogenous sample analyses reveal that the primary sources of soil fluorine are geological formations and the prolonged and intensive use of foreign and Western compound fertilizers. Atmospheric deposition, along with water used for irrigation and pesticides in tea gardens, do not constitute significant sources of fluorine in the surface soil. To mitigate fluorine levels in brick tea, it is advisable for tea gardens to increase the use of organic and nitrogen-based fertilizers while decreasing reliance on compound fertilizers.\u003c/p\u003e","manuscriptTitle":"Distribution Characteristics of Fluorine in the Soil of Brick Tea Plantations in Chibi and the Sources of Pollution","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-21 09:10:03","doi":"10.21203/rs.3.rs-4766502/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b8f0614f-4475-47ca-b6aa-9a7c98a9e882","owner":[],"postedDate":"August 21st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-10-18T01:23:06+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-21 09:10:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4766502","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4766502","identity":"rs-4766502","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}