Feasibility on the Reuse of Waste Drilling Mud for the Treatment of Desertified Soils

Feasibility on the Reuse of Waste Drilling Mud for the Treatment of Desertified Soils | 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 Feasibility on the Reuse of Waste Drilling Mud for the Treatment of Desertified Soils Yiliang Liu, Xing Zhang, Jie Yu, Xiaoli Zhu, Shi Zhou, Ziye Zhang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5106537/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 Drilling mud, composed of clay, bentonite, and potassium humate, can enhance nutrient availability in barren, coarse-textured soils. This study examines drilling mud from a coalfield and adjacent wind-sand land, focusing on its microscopic structure, particle size distribution, heavy metal content, and potential for resource utilization.The analysis reveals that the drilling mud is a solid-liquid mixture with a pH of 6.94 and 68.44% water content. The fine precipitated particles have a smooth surface. Adding drilling mud did not significantly affect soil pH or electrical conductivity, nor did it alter salinization or alkalization levels. However, soil organic matter, total nitrogen, available phosphorus, and rapid-release potassium increased significantly. Total heavy metal levels remained within acceptable limits as per the "Soil Environmental Quality - Risk Control Standard for Soil Pollution of Agricultural Land" (GB15618-2018).The particle size distribution of the mud spans a few micrometers to several hundred micrometers, effectively filling small sandy soil pores and improving particle size distribution. Adding 30% drilling mud significantly reduced medium and fine sand content while increasing clay and silt from 2.5% (CK group) to 12.8% (M3 group), enhancing soil structure and stability. Water retention in sandy soil improved significantly, with the M4 group achieving 20.5% retention compared to 12.3% in the CK group, demonstrating remarkable enhancement. Drilling Mud Desertified Soil Soil Improvement Soil Fertility Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction In drilling operations, drilling fluids are essential for ensuring smooth drilling and are necessary byproducts in the resource extraction industry. They fulfill various functions related to the borehole, including lubricating and cooling the drill string, detecting formation conditions, cleaning drill cuttings, lifting rock cuttings to the surface, stabilizing the borehole, and controlling formation pressure (Yao & Naeth, 2014 ; Zvomuya et al., 2009a ; Zvomuya et al., 2008 ). Waste drilling mud is one of the main pollutants generated during drilling, and due to its chemical stability, it is difficult to degrade under natural conditions and has significant negative environmental impacts. Its main components include bentonite, hydrocarbons, inorganic salts, organic matter, and heavy metals (Brauer & Negendank, 2004 ). The mud is typically fluid or semi-fluid, with a high water content and characteristics such as fine particles, poor gradation, and high viscosity. Studies indicate that in the United States, approximately 6 million cubic meters of drilling waste are produced annually, while China generates over 2 million cubic meters per year, with nearly 50% being directly discharged into the surrounding environment (Ma et al., 2016 ). The large amounts of waste drilling mud pose a substantial potential threat to the surrounding ecological environment, raising concerns among industry professionals. Over the past decades, various management measures have been implemented for waste drilling mud, such as chemical techniques for solid-liquid separation, chemical stabilization, sealing or filling drilling pits, converting mud to cement, injecting it into safe formations or annular spaces, thermal treatment, bioremediation, composting, cultivating earthworms, and land tillage (Ball et al., 2012 ; Brown et al., 2017 ; Dermatas et al., 2003 ; Guarino et al., 2017a ; Guerra et al., 2018 ; Leiva Suárez et al., 2021 ; Rojas-Avelizapa et al., 2007 ). Although the pollutants in drilling mud are generally below environmental risk thresholds, excessive use may increase environmental risks (Jiao et al., 2016 ). Additionally, limitations due to road transportation, high technical requirements, and high costs make many treatment technologies not widely applicable to drilling mud management, presenting a complex and challenging issue (Chen et al., 2015 ; Wang & Hao, 2021 ; Zhu et al., 2018 ; Zvomuya et al., 2009b ). The mud pit solidification method, as a simple and effective treatment approach, involves storing solid-liquid waste generated during drilling in mud pits around the drilling site after simple chemical treatment. The pits are isolated with anti-seepage cloth to prevent spreading, and the upper layer is covered with local loess to restore vegetation or directly cultivate crops. This method has a small environmental impact, is easy to operate, low cost, and effective, and has been widely used in China over the past two decades (Guarino et al., 2017a ). To promote soil improvement and ecological restoration, in-situ remediation technologies using local materials or organic waste have been widely adopted. For example, a unique soft rock in China has been used to improve the Mu Us Desert, which has been shown to enhance soil hydraulic performance and physical structure (Sun & Han, 2018 ). Organic waste, such as bio-humus and waste drilling mud, is also frequently used worldwide to remediate coarse-textured soils (Wang et al., 2021 ; Wesseling et al., 2009 ). Drilling mud contains a substantial amount of organic matter (lignite or lignosulfonates), clay minerals (bentonite), and additives (sodium methyl cellulose and sodium polyphosphate) (Wang et al., 2021 ). Due to its rich nutrient content and soil organic matter, it is considered a potential nutrient reservoir (Fink & Drohan, 2015 ; Fu et al., 2022 ). Current research on in-situ land utilization of waste drilling mud has found that it not only improves the structure of coarse-textured soils but also helps retain moisture and nutrients (Abd El Halim & Lennartz, 2017 ; Xia et al., 2017 ), playing a key role in vegetation restoration and agricultural practices (Bronick & Lal, 2005 ). Tawornpruek studied the application of waste drilling mud in improving sandy soil and found that a mud-to-soil ratio of 1:3 resulted in a water retention of 65.6%, a 55.6% increase compared to the original soil. This indicates that adding waste drilling mud enhances soil water retention (Tawornpruek et al., 2021 ). Water-based drilling mud (WBM) is widely used in drilling and is more environmentally friendly compared to other non-water-based mud (Fu et al., 2022 ). Research shows that the application of drilling mud changes soil porosity, including pore size distribution, pore morphology, and pore range (Whitaker et al., 2016 ; Zvomuya et al., 2008 ), affecting soil water-holding capacity. This change directly impacts soil moisture adsorption, retention, and release, influencing soil hydraulic properties (Bauder et al., 2005 ; Fatichi et al., 2020 ). Yao investigated the addition of up to 60 cubic meters per hectare of potassium silicate drilling fluid to sandy soil, effectively reducing soil total porosity, enhancing soil water retention, and improving the low water retention of sandy soil. The moisture available to plants was significantly increased, and the soil's saturated hydraulic conductivity was reduced (Yao & Naeth, 2014 ). Therefore, the use of drilling mud not only alters the internal structure and pore space distribution of the soil but may also affect the soil's moisture retention capacity, impacting crop growth and soil moisture management. Utilizing drilling mud for land treatment has become a practical and cost-effective alternative, widely applied in areas such as the Loess Plateau (Wang & Hao, 2021 ). 2. Materials and Methods 2.1 Sample Collection and Experimental Design The study area is located in a coal mine in Yuyang District, Yulin City, Shaanxi Province. Waste drilling mud was collected from the drilling site at this coal mine. To ensure consistency in the overall properties of the waste mud before the experiment, it was thoroughly stirred to achieve uniform distribution of its components, thus reducing experimental error. The waste drilling mud studied is classified as water-based drilling mud. After being left to settle for one day, the waste mud did not show significant solid-liquid separation, and the upper liquid remained relatively turbid, similar to the original mud. The waste drilling mud generated from drilling was collected in a buffer tank and, after stirring, gel breaking, and dewatering with a filter press, produced solid mud cakes with a certain moisture content. A portion of the collected waste drilling mud and mud cakes was stored at -20℃ for future use. The collected waste drilling mud, mud cakes, and sandy soil were air-dried and ground, then sieved through a 100-mesh nylon screen. Each 1 kg portion of sandy soil was placed in a plastic bowl. According to the experimental design shown in Table 1 , the sandy soil was thoroughly mixed with the added waste drilling mud and mud cakes, and placed under laboratory conditions for soil aging. During the experiment, the laboratory was well-ventilated and maintained at a temperature between 25 to 35°C. The control group was designated as CK, while the experimental groups were as follows: M1 added 100 g of drilling mud; M2 added 250 g of drilling mud; M3 added 500 g of drilling mud; M4 added 750 g of drilling mud; MC1 added 50 g of mud cake; and MC2 added 100 g of mud cake. Each group was set up in triplicate, and the soil was watered regularly to maintain moisture. After 15 days of mixing, soil samples were collected for testing and analysis. Table 1 Experimental design Numbering Sand soil weight Additive Exerting quantity CK 1kg / 0 g M1 Drilling fluid 100 g M2 Drilling fluid 250 g M3 Drilling fluid 500 g M4 Drilling fluid 750 g MC1 Mud cake 50 g MC2 Mud cake 100 g 2.2 Basic Physicochemical Properties Analysis Before the experiment, the waste drilling mud's morphological characteristics were analyzed using scanning electron microscopy (SEM) for morphology and structure. Particle size distribution was determined with laser diffraction (Malvern MS2000). Samples were air-dried, and basic physicochemical properties are summarized in Table 2 . Soil pH was measured with a pH meter (Leici PHSJ-4F), while electrical conductivity (EC) was assessed using a conductivity meter (Leici DDB-303A) at a 5:1 soil-to-water ratio. Moisture content was determined by drying, cation exchange capacity (CEC) via the cobalt chloride method, and organic matter using high-temperature dichromate oxidation. Total nitrogen (TN), phosphorus (TP and AP), and potassium (AK) were measured using various methods, including flow analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES). Heavy metals were quantified using atomic absorption spectroscopy (AAS) and other specific methods for different metals. Table 2 Physicochemical properties of drilling mud, mud cake and sandy soil Index Drilling fluid Mud cake Sand soil pH 6.94 8.9 6.51 Water content(%) 68.44 0.75 11.71 Cation Exchange Capacity CEC(cmol/kg) 8.87 12.20 4.63 SOM(g/kg) 17.53 26.18 6.23 TOC(g/kg) 10.17 15.19 3.61 TN(g/kg) 0.58 0.79 0.42 TP(g/kg) 0.83 2.12 0.26 AP(mg/kg) 496.54 659.31 28.49 AK(mg/kg) 113.85 171.75 77.91 2.3 Heavy Metal Analysis Before the experiment, the heavy metal content in the drilling mud, mud cakes, and sandy soil was analyzed, and the results are shown in Table 3 . After 15 days of mixing, soil samples were collected to analyze heavy metals and their forms. The samples were air-dried, impurities were removed, and the samples were ground and sieved through a 100-mesh screen. Heavy metal content was determined using the method described above. Table 3 Pollutant content mg/kg Index Drilling fluid Mud cake Sand soil Pb 32.16 38.1076 37.906 Cd 0.35 0.3762 0.044 Cr 52.71 66.1681 10.435 As 1.34 1.1430 2.193 Ni < 0.05 < 0.05 57.642 Cu 10.81 22.7799 21.292 Zn 51.83 60.7459 53.489 Hg < 0.04 < 0.04 < 0.01 2.4 Analysis of Water Holding and Retention Properties Soil particle size distribution was measured using a laser particle size analyzer. The fractal dimension was calculated using the following formula: $$\:\frac{\text{V}(\text{r}<{\text{R}}_{\text{i}})}{{\text{V}}_{\text{r}}}={\left(\frac{{\text{R}}_{\text{i}}}{{\text{R}}_{\text{m}\text{a}\text{x}}}\right)}^{3}\text{D}$$ 1 Where: \(\:\text{r}\) is the particle size; \(\:{\text{R}}_{\text{i}}\) is the particle size at the \(\:\text{i}\) -th level; \(\:\text{V}(\text{r}<{\text{R}}_{\text{i}})\) is the volume of soil particles smaller than \(\:{\text{R}}_{\text{i}}\) ; \(\:{\text{R}}_{\text{m}\text{a}\text{x}}\) is the maximum particle size; \(\:\text{D}\) is the fractal dimension value. Soil permeability of the mixed soil was analyzed as follows: Samples were passed through a standard sieve with a 2 mm mesh size. Two cylindrical glass columns were prepared, with cotton, filter paper, and the sample added in sequence. The sample was filled to about 5 cm from the top of the column, followed by two layers of filter paper, then compacted slightly and topped with a funnel. An equal amount of clean water was prepared and poured steadily from the top of the column while timing was started. The water head height was kept constant, and the infiltration depth was recorded at regular intervals to determine the relationship between infiltration depth and time. Soil water holding capacity was measured using the weighing method. The calculation formula is: \(\:\text{W}\text{a}\text{t}\text{e}\text{r}\:\text{H}\text{o}\text{l}\text{d}\text{i}\text{n}\text{g}\:\text{C}\text{a}\text{p}\text{a}\text{c}\text{i}\text{t}\text{y}=\left(\frac{{\text{m}}_{1}-{\text{m}}_{\text{j}}}{{\text{m}}_{1}}\right)\times\:\) 100%(2) where \(\:{\text{m}}_{1}\) is the initial mass of the sample (g) and \(\:{\text{m}}_{\text{j}}\) is the mass of the sample at a given time (g). 2.5 Statistical Analysis During the experiment, different numbers of experimental blanks were set according to the number of samples. Three parallel samples were measured for each batch. Data processing and analysis were performed using Excel 2021 and IBM SPSS Statistics 25. Some charts were created using Origin 2021 and R Studio. 3. Results and Discussion 3.1 Composition of the Waste Drilling Mud in the Study Area The measurement results show that the particle size of the drilling mud is mostly distributed between 1–10 µm, with a predominance of clay particles, while particles larger than 100 µm are almost absent. This indicates that the drilling mud particles are very fine and uniform(Luo et al., 2022 ). The distribution of particles mainly within the 1–10 µm range and the absence of particles larger than 100 µm suggest that the drilling mud has very fine and uniform particles (Murtaza et al., 2023 ), predominantly clayey. This has several implications:(1) The fine and uniform particles may result in better rheological properties of the mud (Lu et al., 2017 ).(2)The small particles help in sealing fractures and pores, reducing the risk of liquid leakage (Retnanto et al., 2023 ).(3)The uniformly distributed fine particles can enhance the adhesion of the mud to other substances (Wang et al., 2022 ). When mixed with coarser soil, this fine drilling mud can facilitate thorough mixing with the soil and may affect the soil's water retention properties (Tawornpruek et al., 2021 ). Scanning electron microscopy (SEM) was used to characterize the drilling mud while minimizing damage and contamination to its original morphology. The characterization results are shown in Fig. 2. The SEM images reveal that the surface of the drilling mud is finely distributed with very small, irregularly shaped pores and no significant folding structures. The surface is relatively smooth and consists of particulate matter. The energy-dispersive X-ray spectroscopy (EDS) analysis indicates that the drilling mud is rich in oxygen (O), silicon (Si), and a small amount of carbon (C). This is due to the presence of a significant amount of water molecules and silicates in the mud (Yatsenko et al., 2021 ). Additionally, since the mud is from underground, it may contain residual microorganisms or organic matter, which includes carbon. 3.2 Physicochemical Properties of Mixed Soils Table 4 Basic Physicochemical Properties of Mixed Soils Index CK Drilling fluid Mud cake M1 M2 M3 M4 MC1 MC2 pH 6.51 ± 0.01g 6.54 ± 0.006f 6.63 ± 0.02d 6.72 ± 0.02c 6.85 ± 0.06a 6.58 ± 0.06e 6.76 ± 0.06b EC(µs/cm) 129.8 ± 0.06c 204 ± 0.58b 212 ± 2.00a 130.6 ± 0.06c 114.7 ± 0.07d 67.3 ± 0.29f 71.7 ± 0.23e CEC(cmol/kg) 4.63 ± 0.04d 9.92 ± 0.11b 10.16 ± 0.76b 12.94 ± 0.47a 6.20 ± 0.15c 5.37 ± 0.23d 6.68 ± 0.34c SOM(g/kg) 6.23 ± 0.04f 8.11 ± 0.05e 10.92 ± 0.06d 15.62 ± 0.08b 19.32 ± 0.39a 11.16 ± 0.31d 14.65 ± 0.03c SOC(g/kg) 3.61 ± 0.06f 4.70 ± 0.07e 6.33 ± 0.1d 9.06 ± 0.13b 11.21 ± 0.68a 6.47 ± 0.53d 8.50 ± 0.04c TN(g/kg) 0.42 ± 0.11a 0.44 ± 0.01a 0.46 ± 0.01a 0.50 ± 0.03a 0.54 ± 0.06a 0.44 ± 0.07a 0.47 ± 0.05a AP(mg/kg) 28.49 ± 1.85e 92.29 ± 7.24d 339.01 ± 7.85a 291.59 ± 1.26b 313.28 ± 15.04a 241.97 ± 26.27c 320.81 ± 21.17a AK(mg/kg) 77.91 ± 0.96e 117.56 ± 1.74d 127.35 ± 3.27c 187.35 ± 1.48a 153.47 ± 2.67b 80.82 ± 0.72e 130.20 ± 0.72c The different letters indicate statistical differences between the groups (one-way ANOVA test); small letters represent a 5% significance level. (1) pH and EC Since the pH of the drilling mud and mud cake is higher than that of the CK soil, the soil pH increases with the amount of added mud. The pH values of the treated soils remain neutral, indicating that the application of drilling mud and mud cake does not lead to soil salinization or alkalization. With increasing amounts of mud, the EC values of the M1, M2, and M3 groups were higher than that of the CK group, but the EC actually decreased with higher amounts of drilling mud. This may be due to the high salt content in the mud, which increases the concentration of salt ions in the soil. The surface of the mud, rich in cations, forms a diffuse layer that increases soil conductivity (Choo et al., 2016 ). Additionally, the water-based drilling mud contains additives such as polyacrylamide potassium salt, carboxymethyl cellulose sodium salt, sulfonates, NaOH, and CaCl, which increase the salt ion content. With more mud added, some salt ions may precipitate with ions in the soil, leading to a relative dilution of other ions and a decrease in overall conductivity (Yang et al., 2022 ). The EC is closely related to soil particle size and texture (Dong et al., 2022 ). (2) SOM and TOC In the CK group, the soil SOM was 6.23 g·kg⁻¹, while in the treatment groups M1, M2, M3, M4, MC1, and MC2, the SOM values were higher, at 8.11 g·kg⁻¹, 10.92 g·kg⁻¹, 15.62 g·kg⁻¹, 19.32 g·kg⁻¹, 11.16 g·kg⁻¹, and 14.65 g·kg⁻¹, respectively. This indicates that the SOM increases with the amount of drilling mud applied (Wang et al., 2023 ). The drilling mud itself contains higher levels of organic matter compared to sand soil, so increasing the amount of drilling mud raises the soil's organic matter and carbon content. Increasing soil organic matter improves soil fertility and nutrient status, enhances water and nutrient retention, promotes plant growth and development, and improves the nutrient status of poor soils (El-Naggar et al., 2019 ). (3) Cation Exchange Capacity (CEC) The CEC of the CK group was 4.63 cmol·kg⁻¹. With increasing amounts of drilling mud, the CEC also increased, with the order from highest to lowest being: M3 > M2 > M1 > MC2 > M4 > MC1 > CK. The CEC of the M3 group was 12.94 cmol·kg⁻¹, which is 2.79 times that of the CK group. The CEC initially increased and then decreased with more drilling mud applied. Some components in the drilling mud may release soluble cations, such as sodium and potassium, which exchange with metal ions in the soil (Nel et al., 2023 ), thus increasing soil CEC. Under the same application conditions, the CEC of the drilling mud is higher than that of the mud cake, possibly because the drilling mud has a finer texture, and finer materials generally possess higher CEC(Bi et al., 2023 ). The SEM-EDS results show that the drilling mud contains Ca ions. During the formation of the mud, alkaline substances like calcium oxide and calcium hydroxide are added to adjust pH. As the amount of drilling mud increases, excessive alkaline cations in the M4 group may form inorganic carbonate precipitates with dissolved inorganic carbon, leading to a decrease in soil CEC (Renforth & Henderson, 2017 )\. The lower water content in MC1, M4, and MC2, compared to other treatment groups, also leads to a smaller specific surface area and a relatively lower cation exchange capacity (Bi et al., 2023 ). (4) Available Phosphorus (AP), Available Potassium (AK), and Total Nitrogen (TN) The total nitrogen content increased with the amount of drilling mud applied. AP and AK contents increased significantly with the addition of drilling mud. The high salt content in water-based drilling mud is due to low weathering of rock debris, rich in Ca, Mg, K, and Na elements; additionally, the drilling mud contains additives such as polyacrylamide potassium salt, carboxymethyl cellulose sodium salt, sulfonates, phosphates, NaOH, and CaCl2, resulting in higher phosphorus and potassium content. With increased amounts of drilling mud, the AP content initially increased and then decreased. The SEM-EDS results show that the drilling mud contains Fe³⁺, Al³⁺, Ca²⁺, and other metal ions. These ions may chelate with phosphorus in the soil to form more stable compounds, reducing the amount of available phosphorus in the soil (Ge et al., 2020 ). Additionally, because the drilling mud is a mixture of solids and liquids, its uneven distribution in the soil can cause fluctuations in the available phosphorus content. The available potassium content increased with mud application but then decreased, possibly due to excessive mud affecting short-term mineralization and absorption. High available phosphorus allows plants to more easily absorb phosphorus, aiding root development, flowering, fruiting, and crop yield. Available potassium helps regulate plant water balance, enhances stress resistance, promotes nutrient transport, and increases fruit quality and quantity (Li & Li, 2022 ). Thus, the application of drilling mud can effectively improve nutrient availability in sandy soil and increase soil fertility. 3.3 Heavy Metals in Mixed Soils and Their Correlation with Physicochemical Properties Table 5 Total amount of heavy metals in soil mg/kg Group Heavy metal Cr Cu Zn As Cd Pb Hg Ni Risk screening value 200 100 250 30 0.6 120 2.4 100 CK 10.435 ± 0.03 21.292 ± 0.04 53.489 ± 0.46 2.193 ± 0.05 0.044 ± 0.003 37.906 ± 0.49 < 0.01 57.642 ± 0.30 M1 18.648 ± 0.27 38.305 ± 0.21 131.580 ± 4.27 1.839 ± 0.03 0.023 ± 0.003 30.770 ± 0.03 < 0.01 58.476 ± 0.25 M2 19.504 ± 0.20 37.512 ± 0.48 114.634 ± 1.18 2.432 ± 0.01 0.128 ± 0.003 44.437 ± 0.04 < 0.01 59.634 ± 0.24 M3 27.312 ± 0.26 44.863 ± 0.60 124.716 ± 2.04 3.963 ± 0.08 0.196 ± 0.004 82.720 ± 0.12 < 0.01 60.246 ± 0.12 M4 33.535 ± 0.55 58.371 ± 0.45 157.025 ± 1.29 5.012 ± 0.01 0.295 ± 0.02 38.709 ± 0.23 < 0.01 65.453 ± 0.32 MC1 17.676 ± 0.25 34.930 ± 0.25 64.556 ± 0.67 1.980 ± 0.02 0.092 ± 0.001 53.023 ± 0.53 < 0.01 48.637 ± 0.04 MC2 25.191 ± 0.25 42.833 ± 0.12 97.187 ± 0.62 2.616 ± 0.03 0.174 ± 0.0010 107.858 ± 0.66 < 0.01 68.769 ± 0.19 Table 5 shows the measurement results for heavy metal content in the soils.Overall, the data reveal that the levels of heavy metals in the mixed soils vary with the amount of drilling mud and mud cake added. Soils with 75% drilling mud had the highest concentrations of Cr, Cu, Zn, As, and Cd, at 33.53 mg·kg⁻¹, 58.37 mg·kg⁻¹, 157.03 mg·kg⁻¹, 5.01 mg·kg⁻¹, and 6.33 mg·kg⁻¹, respectively. The Pb concentration in all groups was < 0.01 mg·kg⁻¹. The highest Pb²⁺ concentration was found in soils with 75% drilling mud, at 82.72 mg·kg⁻¹. According to the 'Soil Table 5 Total amount of heavy metals in soil. Environmental Quality Agricultural Land Soil Pollution Risk Control Standard GB15618-2018' (Yang et al., 2022 ), the risk of heavy metal pollution in these mixed soils does not exceed the limits, which indicates that the risk of heavy metal pollution in soils mixed with drilling mud and mud cake is relatively low. From the correlation analysis results in Fig. 3 , it can be seen that pH shows a positive correlation with heavy metals Cr, Cu, Zn, As, and Cd. The strong correlation among these heavy metals indicates a certain degree of similarity in their sources. As soil pH increases, the negative charges on the surfaces of clay minerals, hydrated oxides, and organic matter in the soil increase, significantly enhancing electrostatic attraction and the number of active sites. This promotes electrostatic adsorption and tighter specific adsorption processes. On the other hand, the decrease in H + concentration effectively reduces its competitive adsorption with heavy metal ions, thereby promoting the adsorption of heavy metal ions by soil particles (Bernal & McGrath, 1994 ). There is a significant negative correlation between pH and EC values, indicating that the increase in pH due to the addition of drilling mud is a key reason for the decrease in EC in the mixed soil. This is because the solubility of ions (such as metal ions) decreases as soil pH increases. Cr, Cu, As, and Cd show positive correlations with SOM and SOC, suggesting that SOM and SOC in the mixed soil may form complexes with Cr, Cu, As, and Cd ions, reducing the mobility of these heavy metals and leading to their accumulation in the mixed soil (Zheng et al., 2023 ). 3.4 Structure of Drilling Mud and Water Retention Performance of Mixed Soil The pore distribution in sandy soil is uneven, with more large pores and fewer small pores, resulting in loose soil. This condition exacerbates soil erosion caused by wind and water, leading to issues such as dust pollution and loss of soil nutrients. Therefore, improving the pore distribution in sandy soil is an important method for soil stabilization (Dai et al., 2019 ). The particle size distribution of the drilling mud is shown in Fig. 4 . Generally, drilling mud undergoes repeated grinding by the drill bit and continuous circulation during the drilling process, dispersing the particles. These particles can form colloidal particles, which help maintain the performance of the mud. This is one of the reasons for its low density and high viscosity. The suspended particles in the mud also affect the mud's performance, with particle sizes generally ranging from a few microns to several hundred microns.The particle size of sandy soil is relatively large, and there is a lack of cementing substances among the particles, making it difficult to form a stable aggregate structure. Therefore, improving the particle distribution of sandy soil and enhancing its stability are important prerequisites for sand control (Reza Vaezi et al., 2020 ). Table 6 Fractal Dimensions of Mixed Soils Group Percentage of soil particle size composition Fractal dimension R 2 0.5 CK 1.735f 3.835f 2.704g 2.509f 36.289a 48.312a 4.616a 2.465c 0.95 M1 10.855d 62.628b 19.828c 6.687c 0d 0c 0c 2.8459a 0.57 M2 13.388c 55.165d 22.451a 7.395a 1.601c 0c 0c 2.8548a 0.61 M3 15.921a 62.823b 16.961d 4.296d 0d 0c 0c 2.8736a 0.57 M4 10.783d 60.721c 21.514b 6.928b 0.054d 0c 0c 2.8442a 0.58 MC1 7.509e 22.577e 5.617f 1.376g 16.447b 43.1b 3.373b 2.7131b 0.95 MC2 15.155b 66.67a 15.143e 3.034e 0d 0c 0c 2.8726a 0.55 The different letters indicate statistical differences between the groups (one-way ANOVA test); small letters represent a 5% significance level. The fractal dimension is a quantitative parameter that characterizes the irregularity and complexity of soil's fractal parameters. A higher fractal dimension indicates a more regular and stable soil pore structure (Guarino et al., 2017b ). The overall characteristics of soil particle fractal dimensions under different treatments are shown in Table 6 . Research indicates that the average fractal dimensions for the six treatments range between 2.84 and 2.87, with a trend towards increasing fine particles. The fractal dimension values for different treatments are ranked as follows: M3 > MC2 > M2 > M1 > M4 > MC1 > CK. A higher volume of clay and silt particles generally corresponds to a higher fractal dimension, indicating better soil structure. This suggests that applying drilling mud and cuttings can help improve the structural properties and stability of sandy soils to some extent. The parameter 'a' of the Kostiakov one-dimensional infiltration model ranges from 0.04856 to 51.52251 for different treatments. As 'K' increases, the slope of the soil moisture infiltration curve also increases, and soil moisture infiltration accelerates. Overall, the infiltration rates for different treatments are CK > M2 > M1 > MC1 > M3 > MC2 > M4. This may be because the drilling mud and cake alter the original soil structure upon entering the soil, rebind with the organic matter in the sandy soil, and form cementitious materials, which causes microaggregates in the soil to reassemble into larger aggregates (Puget et al., 2000 ), thereby inhibiting soil moisture infiltration. Some studies (Dinka et al., 2013 ; Razmi & Sepaskhah, 2012 ; Zaher et al., 2005 ) also found that soil pore blockage caused by dispersed clay particles is one of the reasons for the drastic reduction in water infiltration. Soil physicochemical properties are the main factors affecting the soil infiltration process. Specifically, reduced soil porosity leads to decreased infiltration rate (Hussain et al., 2021 ). Soil texture, bulk density, and soil aggregation also significantly affect soil moisture infiltration (Jeffery et al., 2015 ; Lim et al., 2016 ). The experiment demonstrates that adding drilling mud can effectively delay the infiltration rate of clean water into the soil. This is because the mud particles are very fine, mostly clay, and the solid micro-particles in the drilling mud fill the voids, hindering water infiltration. Additionally, the swelling of polymers and intermolecular bonding also restrict the sample's infiltration. The M4 group exhibited the best water retention performance. This indicates that as the proportion of drilling mud increases, the water retention performance of the soil improves significantly. This is because, as the ratio of drilling mud to sand increases, the free water in the sand is enhanced by molecular interactions, adsorption, and bonding. Moreover, drilling mud contains a significant amount of clay particles, which promote cohesion between sand particles. Therefore, with an increasing ratio of drilling mud, water retention performance also improves. Hydrophilic polymers, such as polyacrylamide, which act as water-holding agents during drilling, have been proven to increase soil water retention (Geesing & Schmidhalter, 2004 ). The addition of small-sized mud particles between large soil particles acts as a bridging agent after compaction and infiltration, altering the soil pore structure. This not only increases soil permeability but also enhances the overall water absorption capacity of large and small particles, leading to improved overall water retention performance. Specifically, the fine particles or clay in the drilling mud fill the larger pores in the sandy soil, causing pore blockage (Bagarello et al., 2007 ; Castellini et al., 2015 ; Herath et al., 2013 ). Soil pore blockage ultimately results in increased water retention. Further comparative analysis reveals that changes in soil water retention are consistent with changes in soil permeability and particle size distribution, though the peak positions differ. This indicates that the particle size distribution of the soil affects changes in water retention. This result is similar to previous findings that drilling mud can help sandy soil form a better structure, increase soil moisture infiltration, and enhance soil water storage (Zvomuya et al., 2009b ). 4. Conclusion The experiment showed that the addition of drilling mud and cake improved various soil properties. Soil pH increased from 6.51 (CK) to 6.85 (M4), indicating a neutral change without salinization. EC values in M1, M2, and M3 were higher than CK, but decreased with increasing mud amount. Soil organic matter (SOM) and organic carbon (TOC) increased with mud application, with SOM rising from 6.23 g·kg^ -1 (CK) to 19.32 g·kg^ -1 (M4). CEC in M3 reached 12.94 cmol·kg^ -1 , 2.79 times higher than CK. Available phosphorus was highest in M2 (339.01 mg·kg^ -1 ), while readily available potassium was highest in M3 (187.35 mg·kg^ -1 ). Total nitrogen content increased with mud amount.The total amount of heavy metals in the soil increased with the application of drilling mud and cake. According to the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard" (GB15618-2018), the risk of heavy metal pollution in the agricultural soil did not reach the threshold. The water holding and retention properties of the mixed soil exhibited significant differences under various amounts of drilling mud and cake. The infiltration rate decreased over time and eventually stabilized. The trend of infiltration rate was similar across different amounts, but the infiltration rate in the drilling mud-treated soils was significantly lower than in the sandy soil control group. This is primarily due to the alteration of the soil structure by the drilling mud, which causes the fine particles to reaggregate into larger aggregates, thereby reducing water infiltration. The infiltration rate ranking for different treatments was CK > M2 > M1 > MC1 > M3 > MC2 > M4, indicating that the addition of drilling mud and cake significantly reduced the infiltration rate.The water retention performance of the soil increased with the amount of drilling mud applied. Compared to the CK group, most treatment groups showed improved water retention performance, with the M4 group exhibiting the best performance. The fine particles in the drilling mud filled the larger pores in the sandy soil, enhancing the overall water retention capacity. This improvement is closely related to the hydrophilic polymers in the mud, such as polyacrylamide, which help enhance soil water retention. Overall, the application of drilling mud not only improved the particle size distribution of sandy soil but also effectively enhanced the soil's water retention capability. However, excessive water retention might lead to poor plant growth, so the proportion of drilling mud should be adjusted based on the actual needs to achieve optimal soil stabilization results. Declarations Conflicts of Interest: The authors declare no conflicts of interest. Funding: The authors gratefully acknowledge the financial support provided by the National Key Research and Development Program of China (Grant No. 2021YFC1808902), Agricultural Science and Technology Innovation Project of Shaanxi Province (Grant No. NYJK-2022-XA-02) and Key Research and Development Program of Shaanxi Province (Grant No. 2019NY-200; 2020ZDLNY06-06; 2020ZDLNY07-10), Northwest University Graduate Innovation Project (Grant No. 363052204001). Author Contribution Conceptualization, Yiliang Liu and Xing Zhang; methodology, Yiliang Liu, Jie Yu, and Xing Zhang; software, Yiliang Liu; validation, Xiaoli Zhu, Ziye Zhang, and Jie Yu; formal analysis, Yiliang Liu and Jie Yu; investigation, Yiliang Liu and Xing Zhang; resources, Yiliang Liu and Shi Zhou; data curation, Shi Zhou; writing—original draft preparation, Yiliang Liu and Xing Zhang; writing—review and editing, Xing Zhang; visualization, Xiaoli Zhu; supervision, Shi Zhou; funding acquisition, Xiaoli Zhu. All authors have read and agreed to the published version of the manuscript. References Abd El Halim AA , Lennartz B (2017) Amendment with sugarcane pith improves the hydrophysical characteristics of saline‐sodic soil. European Journal of Soil Science 68: 327-335. Bagarello V, Castellini M , Iovino M (2007) Comparison of unconfined and confined unsaturated hydraulic conductivity. Geoderma 137: 394-400. 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Zvomuya F, Larney FJ, DeMaere PR , Olson AF (2009b) Hydraulic properties of a sandy loam soil following spent drilling mud application on native prairie. Soil Science Society of America Journal 73: 1108-1112. Zvomuya F, Larney FJ, McGinn SM, Olson AF , Willms WD (2008) Surface Albedo and Soil Heat Flux Changes Following Drilling Mud Application to a Semiarid, Mixed-Grass Prairie. Soil Science Society of America Journal 72: 1217-1225. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5106537","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":373599193,"identity":"6ae28cde-ff51-4110-ac45-adea2c3ddfc8","order_by":0,"name":"Yiliang Liu","email":"","orcid":"","institution":"Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Yiliang","middleName":"","lastName":"Liu","suffix":""},{"id":373599194,"identity":"9f290315-8886-4742-9cd2-2f963c3b9506","order_by":1,"name":"Xing Zhang","email":"","orcid":"","institution":"Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Xing","middleName":"","lastName":"Zhang","suffix":""},{"id":373599195,"identity":"19932fdf-e305-40a1-ad18-d612e41ba0fb","order_by":2,"name":"Jie Yu","email":"","orcid":"","institution":"Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Jie","middleName":"","lastName":"Yu","suffix":""},{"id":373599196,"identity":"ac38bf9f-8a3c-4f93-a5b3-a673bf99bb42","order_by":3,"name":"Xiaoli Zhu","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3UlEQVRIie3RMQrCMBSA4UggXQJdW6R3eFBoF/EsCYKTFMHFqRS6dy94iHiDQMEuBVdLl7p0UnASBEEb3RxiwcUhP8nwhi8hBCGT6R/D/W4BMWQlr3mUDCJMESqHEhVTy2EDCZT42LJlHEF93o0pmnhC4q7VETclPjAgK2iieU/mvpAkBB2xMQocBpSLZhE0FBVcSEocHSHYuvbE4aKuFHl8Jzam6hbg4kAVkd+Jm9JV/xbG82oR3jYw8/OCBFoC+3LbXu4xz8rKh9N66mVl2mnJ5wno/bkmk8lk+q0ncNNEw27dRYoAAAAASUVORK5CYII=","orcid":"","institution":"Northwest University","correspondingAuthor":true,"prefix":"","firstName":"Xiaoli","middleName":"","lastName":"Zhu","suffix":""},{"id":373599197,"identity":"1e7f5bdb-e41c-421d-9bc6-3b8348b5bb52","order_by":4,"name":"Shi Zhou","email":"","orcid":"","institution":"Northwest University","correspondingAuthor":false,"prefix":"","firstName":"Shi","middleName":"","lastName":"Zhou","suffix":""},{"id":373599198,"identity":"2d01d652-06cc-4f4d-a4d6-2e9e94626cc4","order_by":5,"name":"Ziye Zhang","email":"","orcid":"","institution":"Xi’an Jinborui Ecological Tech. Co., Ltd","correspondingAuthor":false,"prefix":"","firstName":"Ziye","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-09-18 03:21:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5106537/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5106537/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":68515202,"identity":"b2e8e256-88fd-41e8-88d1-d66ec077204e","added_by":"auto","created_at":"2024-11-08 06:40:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":53219,"visible":true,"origin":"","legend":"\u003cp\u003eOverview of the study area\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/76309f7f54cd3cd9c929119a.png"},{"id":68515207,"identity":"beb5f919-07fa-4479-9b02-e05db4ef4eb6","added_by":"auto","created_at":"2024-11-08 06:40:27","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":141869,"visible":true,"origin":"","legend":"\u003cp\u003eSEM-EDS scanning electron microscopy\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/e19155db01a92822cb15b98c.png"},{"id":68515205,"identity":"0cb4afdf-40c0-4264-9836-0e9b6fe0d4e4","added_by":"auto","created_at":"2024-11-08 06:40:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":140404,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation Heatmap of Heavy Metals and Soil Physicochemical Properties.Note : Blue indicates a positive correlation, Red indicates a negative correlation, and * indicates a significant level of 0.05.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/4d4077fbe52743f026967c2d.png"},{"id":68515229,"identity":"fd6f9769-1ae8-41d5-9852-a9c302aadd6b","added_by":"auto","created_at":"2024-11-08 06:40:44","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":20008,"visible":true,"origin":"","legend":"\u003cp\u003eDrilling mud size distribution\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/ba725a4f771c999737a67f0b.png"},{"id":68515201,"identity":"e6c0fad8-86f9-42a7-a004-f7d29da2688f","added_by":"auto","created_at":"2024-11-08 06:40:21","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":93900,"visible":true,"origin":"","legend":"\u003cp\u003eParticle Size Distribution of Mixed Soil\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/96ee1d306a58d434136e4321.png"},{"id":68515203,"identity":"33620a45-555c-4a16-886f-f25ee87469ee","added_by":"auto","created_at":"2024-11-08 06:40:24","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":89727,"visible":true,"origin":"","legend":"\u003cp\u003eVariation Curve of Infiltration Rate with Time for Mixed Soils.Figs.a-g represent CK, M1, M2, M3, M4, MC1 and MC2, respectively.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/5814b6274e2cc39e340b4bc9.png"},{"id":68515206,"identity":"882c16a7-e92d-409a-8a40-1a517138b569","added_by":"auto","created_at":"2024-11-08 06:40:27","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":58130,"visible":true,"origin":"","legend":"\u003cp\u003eWater Content vs. Time for Mixed Soils\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/deb062c65d0465ba09bb1249.png"},{"id":70427160,"identity":"dd99c084-7dc5-4a40-bd48-9212ff62a789","added_by":"auto","created_at":"2024-12-03 05:24:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1345280,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5106537/v1/77ad14de-9cde-4a78-9c7e-3c31145f941d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Feasibility on the Reuse of Waste Drilling Mud for the Treatment of Desertified Soils","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eIn drilling operations, drilling fluids are essential for ensuring smooth drilling and are necessary byproducts in the resource extraction industry. They fulfill various functions related to the borehole, including lubricating and cooling the drill string, detecting formation conditions, cleaning drill cuttings, lifting rock cuttings to the surface, stabilizing the borehole, and controlling formation pressure (Yao \u0026amp; Naeth, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Zvomuya et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2009a\u003c/span\u003e; Zvomuya et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). Waste drilling mud is one of the main pollutants generated during drilling, and due to its chemical stability, it is difficult to degrade under natural conditions and has significant negative environmental impacts. Its main components include bentonite, hydrocarbons, inorganic salts, organic matter, and heavy metals (Brauer \u0026amp; Negendank, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). The mud is typically fluid or semi-fluid, with a high water content and characteristics such as fine particles, poor gradation, and high viscosity. Studies indicate that in the United States, approximately 6\u0026nbsp;million cubic meters of drilling waste are produced annually, while China generates over 2\u0026nbsp;million cubic meters per year, with nearly 50% being directly discharged into the surrounding environment (Ma et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The large amounts of waste drilling mud pose a substantial potential threat to the surrounding ecological environment, raising concerns among industry professionals.\u003c/p\u003e \u003cp\u003eOver the past decades, various management measures have been implemented for waste drilling mud, such as chemical techniques for solid-liquid separation, chemical stabilization, sealing or filling drilling pits, converting mud to cement, injecting it into safe formations or annular spaces, thermal treatment, bioremediation, composting, cultivating earthworms, and land tillage (Ball et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Brown et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Dermatas et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2003\u003c/span\u003e; Guarino et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e; Guerra et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Leiva Su\u0026aacute;rez et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Rojas-Avelizapa et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Although the pollutants in drilling mud are generally below environmental risk thresholds, excessive use may increase environmental risks (Jiao et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Additionally, limitations due to road transportation, high technical requirements, and high costs make many treatment technologies not widely applicable to drilling mud management, presenting a complex and challenging issue (Chen et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Wang \u0026amp; Hao, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zhu et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Zvomuya et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2009b\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe mud pit solidification method, as a simple and effective treatment approach, involves storing solid-liquid waste generated during drilling in mud pits around the drilling site after simple chemical treatment. The pits are isolated with anti-seepage cloth to prevent spreading, and the upper layer is covered with local loess to restore vegetation or directly cultivate crops. This method has a small environmental impact, is easy to operate, low cost, and effective, and has been widely used in China over the past two decades (Guarino et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017a\u003c/span\u003e). To promote soil improvement and ecological restoration, in-situ remediation technologies using local materials or organic waste have been widely adopted. For example, a unique soft rock in China has been used to improve the Mu Us Desert, which has been shown to enhance soil hydraulic performance and physical structure (Sun \u0026amp; Han, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Organic waste, such as bio-humus and waste drilling mud, is also frequently used worldwide to remediate coarse-textured soils (Wang et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Wesseling et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Drilling mud contains a substantial amount of organic matter (lignite or lignosulfonates), clay minerals (bentonite), and additives (sodium methyl cellulose and sodium polyphosphate) (Wang et al., \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Due to its rich nutrient content and soil organic matter, it is considered a potential nutrient reservoir (Fink \u0026amp; Drohan, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Fu et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eCurrent research on in-situ land utilization of waste drilling mud has found that it not only improves the structure of coarse-textured soils but also helps retain moisture and nutrients (Abd El Halim \u0026amp; Lennartz, \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Xia et al., \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), playing a key role in vegetation restoration and agricultural practices (Bronick \u0026amp; Lal, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Tawornpruek studied the application of waste drilling mud in improving sandy soil and found that a mud-to-soil ratio of 1:3 resulted in a water retention of 65.6%, a 55.6% increase compared to the original soil. This indicates that adding waste drilling mud enhances soil water retention (Tawornpruek et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Water-based drilling mud (WBM) is widely used in drilling and is more environmentally friendly compared to other non-water-based mud (Fu et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Research shows that the application of drilling mud changes soil porosity, including pore size distribution, pore morphology, and pore range (Whitaker et al., \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Zvomuya et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2008\u003c/span\u003e), affecting soil water-holding capacity. This change directly impacts soil moisture adsorption, retention, and release, influencing soil hydraulic properties (Bauder et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; Fatichi et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Yao investigated the addition of up to 60 cubic meters per hectare of potassium silicate drilling fluid to sandy soil, effectively reducing soil total porosity, enhancing soil water retention, and improving the low water retention of sandy soil. The moisture available to plants was significantly increased, and the soil's saturated hydraulic conductivity was reduced (Yao \u0026amp; Naeth, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Therefore, the use of drilling mud not only alters the internal structure and pore space distribution of the soil but may also affect the soil's moisture retention capacity, impacting crop growth and soil moisture management. Utilizing drilling mud for land treatment has become a practical and cost-effective alternative, widely applied in areas such as the Loess Plateau (Wang \u0026amp; Hao, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Sample Collection and Experimental Design\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe study area is located in a coal mine in Yuyang District, Yulin City, Shaanxi Province. Waste drilling mud was collected from the drilling site at this coal mine. To ensure consistency in the overall properties of the waste mud before the experiment, it was thoroughly stirred to achieve uniform distribution of its components, thus reducing experimental error. The waste drilling mud studied is classified as water-based drilling mud. After being left to settle for one day, the waste mud did not show significant solid-liquid separation, and the upper liquid remained relatively turbid, similar to the original mud. The waste drilling mud generated from drilling was collected in a buffer tank and, after stirring, gel breaking, and dewatering with a filter press, produced solid mud cakes with a certain moisture content. A portion of the collected waste drilling mud and mud cakes was stored at -20℃ for future use.\u003c/p\u003e \u003cp\u003eThe collected waste drilling mud, mud cakes, and sandy soil were air-dried and ground, then sieved through a 100-mesh nylon screen. Each 1 kg portion of sandy soil was placed in a plastic bowl. According to the experimental design shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the sandy soil was thoroughly mixed with the added waste drilling mud and mud cakes, and placed under laboratory conditions for soil aging. During the experiment, the laboratory was well-ventilated and maintained at a temperature between 25 to 35\u0026deg;C. The control group was designated as CK, while the experimental groups were as follows: M1 added 100 g of drilling mud; M2 added 250 g of drilling mud; M3 added 500 g of drilling mud; M4 added 750 g of drilling mud; MC1 added 50 g of mud cake; and MC2 added 100 g of mud cake. Each group was set up in triplicate, and the soil was watered regularly to maintain moisture. After 15 days of mixing, soil samples were collected for testing and analysis.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eExperimental design\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumbering\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSand soil weight\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAdditive\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eExerting quantity\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"6\" rowspan=\"7\"\u003e \u003cp\u003e1kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e/\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e250 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e500 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e750 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMud cake\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMud cake\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100 g\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Basic Physicochemical Properties Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eBefore the experiment, the waste drilling mud's morphological characteristics were analyzed using scanning electron microscopy (SEM) for morphology and structure. Particle size distribution was determined with laser diffraction (Malvern MS2000). Samples were air-dried, and basic physicochemical properties are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Soil pH was measured with a pH meter (Leici PHSJ-4F), while electrical conductivity (EC) was assessed using a conductivity meter (Leici DDB-303A) at a 5:1 soil-to-water ratio. Moisture content was determined by drying, cation exchange capacity (CEC) via the cobalt chloride method, and organic matter using high-temperature dichromate oxidation. Total nitrogen (TN), phosphorus (TP and AP), and potassium (AK) were measured using various methods, including flow analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES). Heavy metals were quantified using atomic absorption spectroscopy (AAS) and other specific methods for different metals.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysicochemical properties of drilling mud, mud cake and sandy soil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMud cake\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSand soil\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.51\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eWater content(%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e68.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11.71\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCation Exchange Capacity\u003c/p\u003e \u003cp\u003eCEC(cmol/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e8.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.63\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSOM(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e26.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTOC(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15.19\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e3.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTN(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTP(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e2.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAP(mg/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e496.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e659.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28.49\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAK(mg/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e113.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e171.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e77.91\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Heavy Metal Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eBefore the experiment, the heavy metal content in the drilling mud, mud cakes, and sandy soil was analyzed, and the results are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. After 15 days of mixing, soil samples were collected to analyze heavy metals and their forms. The samples were air-dried, impurities were removed, and the samples were ground and sieved through a 100-mesh screen. Heavy metal content was determined using the method described above.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePollutant content mg/kg\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIndex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMud cake\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSand soil\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e32.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e38.1076\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e37.906\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.3762\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.044\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e52.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e66.1681\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e10.435\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.1430\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2.193\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e57.642\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e10.81\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.7799\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e21.292\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eZn\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e51.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e60.7459\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e53.489\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Analysis of Water Holding and Retention Properties\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eSoil particle size distribution was measured using a laser particle size analyzer. The fractal dimension was calculated using the following formula:\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e \u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\frac{\\text{V}(\\text{r}\u0026lt;{\\text{R}}_{\\text{i}})}{{\\text{V}}_{\\text{r}}}={\\left(\\frac{{\\text{R}}_{\\text{i}}}{{\\text{R}}_{\\text{m}\\text{a}\\text{x}}}\\right)}^{3}\\text{D}$$\u003c/div\u003e \u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eWhere:\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{r}\\)\u003c/span\u003e\u003c/span\u003e is the particle size;\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{R}}_{\\text{i}}\\)\u003c/span\u003e\u003c/span\u003e is the particle size at the \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{i}\\)\u003c/span\u003e\u003c/span\u003e-th level;\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{V}(\\text{r}\u0026lt;{\\text{R}}_{\\text{i}})\\)\u003c/span\u003e\u003c/span\u003e is the volume of soil particles smaller than \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{R}}_{\\text{i}}\\)\u003c/span\u003e\u003c/span\u003e;\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{R}}_{\\text{m}\\text{a}\\text{x}}\\)\u003c/span\u003e\u003c/span\u003e is the maximum particle size;\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{D}\\)\u003c/span\u003e\u003c/span\u003e is the fractal dimension value.\u003c/p\u003e \u003cp\u003eSoil permeability of the mixed soil was analyzed as follows: Samples were passed through a standard sieve with a 2 mm mesh size. Two cylindrical glass columns were prepared, with cotton, filter paper, and the sample added in sequence. The sample was filled to about 5 cm from the top of the column, followed by two layers of filter paper, then compacted slightly and topped with a funnel. An equal amount of clean water was prepared and poured steadily from the top of the column while timing was started. The water head height was kept constant, and the infiltration depth was recorded at regular intervals to determine the relationship between infiltration depth and time.\u003c/p\u003e \u003cp\u003eSoil water holding capacity was measured using the weighing method.\u003c/p\u003e \u003cp\u003eThe calculation formula is:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:\\text{W}\\text{a}\\text{t}\\text{e}\\text{r}\\:\\text{H}\\text{o}\\text{l}\\text{d}\\text{i}\\text{n}\\text{g}\\:\\text{C}\\text{a}\\text{p}\\text{a}\\text{c}\\text{i}\\text{t}\\text{y}=\\left(\\frac{{\\text{m}}_{1}-{\\text{m}}_{\\text{j}}}{{\\text{m}}_{1}}\\right)\\times\\:\\)\u003c/span\u003e \u003c/span\u003e100%(2)\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{m}}_{1}\\)\u003c/span\u003e\u003c/span\u003e is the initial mass of the sample (g) and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{m}}_{\\text{j}}\\)\u003c/span\u003e\u003c/span\u003e is the mass of the sample at a given time (g).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Statistical Analysis\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eDuring the experiment, different numbers of experimental blanks were set according to the number of samples. Three parallel samples were measured for each batch. Data processing and analysis were performed using Excel 2021 and IBM SPSS Statistics 25. Some charts were created using Origin 2021 and R Studio.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Composition of the Waste Drilling Mud in the Study Area\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe measurement results show that the particle size of the drilling mud is mostly distributed between 1\u0026ndash;10 \u0026micro;m, with a predominance of clay particles, while particles larger than 100 \u0026micro;m are almost absent. This indicates that the drilling mud particles are very fine and uniform(Luo et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The distribution of particles mainly within the 1\u0026ndash;10 \u0026micro;m range and the absence of particles larger than 100 \u0026micro;m suggest that the drilling mud has very fine and uniform particles (Murtaza et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), predominantly clayey. This has several implications:(1) The fine and uniform particles may result in better rheological properties of the mud (Lu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).(2)The small particles help in sealing fractures and pores, reducing the risk of liquid leakage (Retnanto et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).(3)The uniformly distributed fine particles can enhance the adhesion of the mud to other substances (Wang et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eWhen mixed with coarser soil, this fine drilling mud can facilitate thorough mixing with the soil and may affect the soil's water retention properties (Tawornpruek et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Scanning electron microscopy (SEM) was used to characterize the drilling mud while minimizing damage and contamination to its original morphology. The characterization results are shown in Fig.\u0026nbsp;2. The SEM images reveal that the surface of the drilling mud is finely distributed with very small, irregularly shaped pores and no significant folding structures. The surface is relatively smooth and consists of particulate matter. The energy-dispersive X-ray spectroscopy (EDS) analysis indicates that the drilling mud is rich in oxygen (O), silicon (Si), and a small amount of carbon (C). This is due to the presence of a significant amount of water molecules and silicates in the mud (Yatsenko et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Additionally, since the mud is from underground, it may contain residual microorganisms or organic matter, which includes carbon.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Physicochemical Properties of Mixed Soils\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBasic Physicochemical Properties of Mixed Soils\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eIndex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e \u003cp\u003eDrilling fluid\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c9\" namest=\"c8\"\u003e \u003cp\u003eMud cake\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eM1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eM2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eM3\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eM4\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eMC1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eMC2\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.51\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.72\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.85\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6.58\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e6.76\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06b\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEC(\u0026micro;s/cm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e129.8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e204\u0026thinsp;\u0026plusmn;\u0026thinsp;0.58b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e212\u0026thinsp;\u0026plusmn;\u0026thinsp;2.00a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e130.6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e114.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e67.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.29f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e71.7\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCEC(cmol/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.63\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.76b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.20\u0026thinsp;\u0026plusmn;\u0026thinsp;0.15c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e5.37\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e6.68\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSOM(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10.92\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e15.62\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e19.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.39a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e11.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.31d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e14.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSOC(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.61\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.70\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.06\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e11.21\u0026thinsp;\u0026plusmn;\u0026thinsp;0.68a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e6.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e8.50\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTN(g/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.42\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.46\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.50\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.06a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.44\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.47\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAP(mg/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e28.49\u0026thinsp;\u0026plusmn;\u0026thinsp;1.85e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e92.29\u0026thinsp;\u0026plusmn;\u0026thinsp;7.24d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e339.01\u0026thinsp;\u0026plusmn;\u0026thinsp;7.85a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e291.59\u0026thinsp;\u0026plusmn;\u0026thinsp;1.26b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e313.28\u0026thinsp;\u0026plusmn;\u0026thinsp;15.04a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e241.97\u0026thinsp;\u0026plusmn;\u0026thinsp;26.27c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e320.81\u0026thinsp;\u0026plusmn;\u0026thinsp;21.17a\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAK(mg/kg)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e77.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.96e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e117.56\u0026thinsp;\u0026plusmn;\u0026thinsp;1.74d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e127.35\u0026thinsp;\u0026plusmn;\u0026thinsp;3.27c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e187.35\u0026thinsp;\u0026plusmn;\u0026thinsp;1.48a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e153.47\u0026thinsp;\u0026plusmn;\u0026thinsp;2.67b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e80.82\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e130.20\u0026thinsp;\u0026plusmn;\u0026thinsp;0.72c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe different letters indicate statistical differences between the groups (one-way ANOVA test); small letters represent a 5% significance level.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003e(1) pH and EC\u003c/p\u003e\u003cp\u003eSince the pH of the drilling mud and mud cake is higher than that of the CK soil, the soil pH increases with the amount of added mud. The pH values of the treated soils remain neutral, indicating that the application of drilling mud and mud cake does not lead to soil salinization or alkalization.\u003c/p\u003e\u003cp\u003eWith increasing amounts of mud, the EC values of the M1, M2, and M3 groups were higher than that of the CK group, but the EC actually decreased with higher amounts of drilling mud. This may be due to the high salt content in the mud, which increases the concentration of salt ions in the soil. The surface of the mud, rich in cations, forms a diffuse layer that increases soil conductivity (Choo et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Additionally, the water-based drilling mud contains additives such as polyacrylamide potassium salt, carboxymethyl cellulose sodium salt, sulfonates, NaOH, and CaCl, which increase the salt ion content. With more mud added, some salt ions may precipitate with ions in the soil, leading to a relative dilution of other ions and a decrease in overall conductivity (Yang et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The EC is closely related to soil particle size and texture (Dong et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e(2) SOM and TOC\u003c/p\u003e\u003cp\u003eIn the CK group, the soil SOM was 6.23 g\u0026middot;kg⁻\u0026sup1;, while in the treatment groups M1, M2, M3, M4, MC1, and MC2, the SOM values were higher, at 8.11 g\u0026middot;kg⁻\u0026sup1;, 10.92 g\u0026middot;kg⁻\u0026sup1;, 15.62 g\u0026middot;kg⁻\u0026sup1;, 19.32 g\u0026middot;kg⁻\u0026sup1;, 11.16 g\u0026middot;kg⁻\u0026sup1;, and 14.65 g\u0026middot;kg⁻\u0026sup1;, respectively. This indicates that the SOM increases with the amount of drilling mud applied (Wang et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The drilling mud itself contains higher levels of organic matter compared to sand soil, so increasing the amount of drilling mud raises the soil's organic matter and carbon content. Increasing soil organic matter improves soil fertility and nutrient status, enhances water and nutrient retention, promotes plant growth and development, and improves the nutrient status of poor soils (El-Naggar et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e(3) Cation Exchange Capacity (CEC)\u003c/p\u003e\u003cp\u003eThe CEC of the CK group was 4.63 cmol\u0026middot;kg⁻\u0026sup1;. With increasing amounts of drilling mud, the CEC also increased, with the order from highest to lowest being: M3\u0026thinsp;\u0026gt;\u0026thinsp;M2\u0026thinsp;\u0026gt;\u0026thinsp;M1\u0026thinsp;\u0026gt;\u0026thinsp;MC2\u0026thinsp;\u0026gt;\u0026thinsp;M4\u0026thinsp;\u0026gt;\u0026thinsp;MC1\u0026thinsp;\u0026gt;\u0026thinsp;CK. The CEC of the M3 group was 12.94 cmol\u0026middot;kg⁻\u0026sup1;, which is 2.79 times that of the CK group. The CEC initially increased and then decreased with more drilling mud applied. Some components in the drilling mud may release soluble cations, such as sodium and potassium, which exchange with metal ions in the soil (Nel et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), thus increasing soil CEC. Under the same application conditions, the CEC of the drilling mud is higher than that of the mud cake, possibly because the drilling mud has a finer texture, and finer materials generally possess higher CEC(Bi et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The SEM-EDS results show that the drilling mud contains Ca ions. During the formation of the mud, alkaline substances like calcium oxide and calcium hydroxide are added to adjust pH. As the amount of drilling mud increases, excessive alkaline cations in the M4 group may form inorganic carbonate precipitates with dissolved inorganic carbon, leading to a decrease in soil CEC (Renforth \u0026amp; Henderson, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\\. The lower water content in MC1, M4, and MC2, compared to other treatment groups, also leads to a smaller specific surface area and a relatively lower cation exchange capacity (Bi et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e(4) Available Phosphorus (AP), Available Potassium (AK), and Total Nitrogen (TN)\u003c/p\u003e\u003cp\u003eThe total nitrogen content increased with the amount of drilling mud applied. AP and AK contents increased significantly with the addition of drilling mud. The high salt content in water-based drilling mud is due to low weathering of rock debris, rich in Ca, Mg, K, and Na elements; additionally, the drilling mud contains additives such as polyacrylamide potassium salt, carboxymethyl cellulose sodium salt, sulfonates, phosphates, NaOH, and CaCl2, resulting in higher phosphorus and potassium content.\u003c/p\u003e\u003cp\u003eWith increased amounts of drilling mud, the AP content initially increased and then decreased. The SEM-EDS results show that the drilling mud contains Fe\u0026sup3;⁺, Al\u0026sup3;⁺, Ca\u0026sup2;⁺, and other metal ions. These ions may chelate with phosphorus in the soil to form more stable compounds, reducing the amount of available phosphorus in the soil (Ge et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Additionally, because the drilling mud is a mixture of solids and liquids, its uneven distribution in the soil can cause fluctuations in the available phosphorus content. The available potassium content increased with mud application but then decreased, possibly due to excessive mud affecting short-term mineralization and absorption. High available phosphorus allows plants to more easily absorb phosphorus, aiding root development, flowering, fruiting, and crop yield. Available potassium helps regulate plant water balance, enhances stress resistance, promotes nutrient transport, and increases fruit quality and quantity (Li \u0026amp; Li, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Thus, the application of drilling mud can effectively improve nutrient availability in sandy soil and increase soil fertility.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Heavy Metals in Mixed Soils and Their Correlation with Physicochemical Properties\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTotal amount of heavy metals in soil mg/kg\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"9\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"8\" nameend=\"c9\" namest=\"c2\"\u003e \u003cp\u003eHeavy metal\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCr\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCu\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eZn\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAs\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCd\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ePb\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eHg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eNi\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRisk screening value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e250\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e2.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e100\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.435\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e21.292\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53.489\u0026thinsp;\u0026plusmn;\u0026thinsp;0.46\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.193\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.044\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e37.906\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e57.642\u0026thinsp;\u0026plusmn;\u0026thinsp;0.30\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e18.648\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e38.305\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e131.580\u0026thinsp;\u0026plusmn;\u0026thinsp;4.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.839\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.023\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e30.770\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e58.476\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19.504\u0026thinsp;\u0026plusmn;\u0026thinsp;0.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e37.512\u0026thinsp;\u0026plusmn;\u0026thinsp;0.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e114.634\u0026thinsp;\u0026plusmn;\u0026thinsp;1.18\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.432\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.128\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e44.437\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e59.634\u0026thinsp;\u0026plusmn;\u0026thinsp;0.24\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e27.312\u0026thinsp;\u0026plusmn;\u0026thinsp;0.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e44.863\u0026thinsp;\u0026plusmn;\u0026thinsp;0.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e124.716\u0026thinsp;\u0026plusmn;\u0026thinsp;2.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.963\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.196\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e82.720\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e60.246\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e33.535\u0026thinsp;\u0026plusmn;\u0026thinsp;0.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e58.371\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e157.025\u0026thinsp;\u0026plusmn;\u0026thinsp;1.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.012\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.295\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e38.709\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e65.453\u0026thinsp;\u0026plusmn;\u0026thinsp;0.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17.676\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34.930\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e64.556\u0026thinsp;\u0026plusmn;\u0026thinsp;0.67\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.980\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.092\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e53.023\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e48.637\u0026thinsp;\u0026plusmn;\u0026thinsp;0.04\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25.191\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e42.833\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e97.187\u0026thinsp;\u0026plusmn;\u0026thinsp;0.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.616\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.174\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e107.858\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.01\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e68.769\u0026thinsp;\u0026plusmn;\u0026thinsp;0.19\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the measurement results for heavy metal content in the soils.Overall, the data reveal that the levels of heavy metals in the mixed soils vary with the amount of drilling mud and mud cake added. Soils with 75% drilling mud had the highest concentrations of Cr, Cu, Zn, As, and Cd, at 33.53 mg\u0026middot;kg⁻\u0026sup1;, 58.37 mg\u0026middot;kg⁻\u0026sup1;, 157.03 mg\u0026middot;kg⁻\u0026sup1;, 5.01 mg\u0026middot;kg⁻\u0026sup1;, and 6.33 mg\u0026middot;kg⁻\u0026sup1;, respectively. The Pb concentration in all groups was \u0026lt;\u0026thinsp;0.01 mg\u0026middot;kg⁻\u0026sup1;. The highest Pb\u0026sup2;⁺ concentration was found in soils with 75% drilling mud, at 82.72 mg\u0026middot;kg⁻\u0026sup1;. According to the 'Soil Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e Total amount of heavy metals in soil.\u003c/p\u003e \u003cp\u003eEnvironmental Quality Agricultural Land Soil Pollution Risk Control Standard GB15618-2018' (Yang et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), the risk of heavy metal pollution in these mixed soils does not exceed the limits, which indicates that the risk of heavy metal pollution in soils mixed with drilling mud and mud cake is relatively low.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eFrom the correlation analysis results in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e, it can be seen that pH shows a positive correlation with heavy metals Cr, Cu, Zn, As, and Cd. The strong correlation among these heavy metals indicates a certain degree of similarity in their sources. As soil pH increases, the negative charges on the surfaces of clay minerals, hydrated oxides, and organic matter in the soil increase, significantly enhancing electrostatic attraction and the number of active sites. This promotes electrostatic adsorption and tighter specific adsorption processes. On the other hand, the decrease in H\u0026thinsp;+\u0026thinsp;concentration effectively reduces its competitive adsorption with heavy metal ions, thereby promoting the adsorption of heavy metal ions by soil particles (Bernal \u0026amp; McGrath, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1994\u003c/span\u003e). There is a significant negative correlation between pH and EC values, indicating that the increase in pH due to the addition of drilling mud is a key reason for the decrease in EC in the mixed soil. This is because the solubility of ions (such as metal ions) decreases as soil pH increases.\u003c/p\u003e \u003cp\u003eCr, Cu, As, and Cd show positive correlations with SOM and SOC, suggesting that SOM and SOC in the mixed soil may form complexes with Cr, Cu, As, and Cd ions, reducing the mobility of these heavy metals and leading to their accumulation in the mixed soil (Zheng et al., \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Structure of Drilling Mud and Water Retention Performance of Mixed Soil\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe pore distribution in sandy soil is uneven, with more large pores and fewer small pores, resulting in loose soil. This condition exacerbates soil erosion caused by wind and water, leading to issues such as dust pollution and loss of soil nutrients. Therefore, improving the pore distribution in sandy soil is an important method for soil stabilization (Dai et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The particle size distribution of the drilling mud is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Generally, drilling mud undergoes repeated grinding by the drill bit and continuous circulation during the drilling process, dispersing the particles. These particles can form colloidal particles, which help maintain the performance of the mud. This is one of the reasons for its low density and high viscosity. The suspended particles in the mud also affect the mud's performance, with particle sizes generally ranging from a few microns to several hundred microns.The particle size of sandy soil is relatively large, and there is a lack of cementing substances among the particles, making it difficult to form a stable aggregate structure. Therefore, improving the particle distribution of sandy soil and enhancing its stability are important prerequisites for sand control (Reza Vaezi et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eFractal Dimensions of Mixed Soils\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"7\" nameend=\"c8\" namest=\"c2\"\u003e \u003cp\u003ePercentage of soil particle size composition\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eFractal dimension\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eR\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.002mm\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.002\u0026ndash;0.02\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.02\u0026ndash;0.05\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.05\u0026ndash;0.1\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.1\u0026ndash;0.25\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.25\u0026ndash;0.5\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026gt;0.5\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.735f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.835f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.704g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.509f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e36.289a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e48.312a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.616a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.465c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.855d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e62.628b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e19.828c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.687c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.8459a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13.388c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e55.165d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22.451a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.395a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.601c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.8548a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.921a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e62.823b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e16.961d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.296d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.8736a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.783d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e60.721c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21.514b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.928b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.054d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.8442a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.58\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.509e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22.577e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.617f\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.376g\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e16.447b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e43.1b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e3.373b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.7131b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.95\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.155b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e66.67a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15.143e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.034e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0d\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0c\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e2.8726a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e0.55\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe different letters indicate statistical differences between the groups (one-way ANOVA test); small letters represent a 5% significance level.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe fractal dimension is a quantitative parameter that characterizes the irregularity and complexity of soil's fractal parameters. A higher fractal dimension indicates a more regular and stable soil pore structure (Guarino et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2017b\u003c/span\u003e). The overall characteristics of soil particle fractal dimensions under different treatments are shown in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Research indicates that the average fractal dimensions for the six treatments range between 2.84 and 2.87, with a trend towards increasing fine particles. The fractal dimension values for different treatments are ranked as follows: M3\u0026thinsp;\u0026gt;\u0026thinsp;MC2\u0026thinsp;\u0026gt;\u0026thinsp;M2\u0026thinsp;\u0026gt;\u0026thinsp;M1\u0026thinsp;\u0026gt;\u0026thinsp;M4\u0026thinsp;\u0026gt;\u0026thinsp;MC1\u0026thinsp;\u0026gt;\u0026thinsp;CK. A higher volume of clay and silt particles generally corresponds to a higher fractal dimension, indicating better soil structure. This suggests that applying drilling mud and cuttings can help improve the structural properties and stability of sandy soils to some extent.\u003c/p\u003e \u003cp\u003eThe parameter 'a' of the Kostiakov one-dimensional infiltration model ranges from 0.04856 to 51.52251 for different treatments. As 'K' increases, the slope of the soil moisture infiltration curve also increases, and soil moisture infiltration accelerates. Overall, the infiltration rates for different treatments are CK\u0026thinsp;\u0026gt;\u0026thinsp;M2\u0026thinsp;\u0026gt;\u0026thinsp;M1\u0026thinsp;\u0026gt;\u0026thinsp;MC1\u0026thinsp;\u0026gt;\u0026thinsp;M3\u0026thinsp;\u0026gt;\u0026thinsp;MC2\u0026thinsp;\u0026gt;\u0026thinsp;M4. This may be because the drilling mud and cake alter the original soil structure upon entering the soil, rebind with the organic matter in the sandy soil, and form cementitious materials, which causes microaggregates in the soil to reassemble into larger aggregates (Puget et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2000\u003c/span\u003e), thereby inhibiting soil moisture infiltration. Some studies (Dinka et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Razmi \u0026amp; Sepaskhah, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Zaher et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2005\u003c/span\u003e) also found that soil pore blockage caused by dispersed clay particles is one of the reasons for the drastic reduction in water infiltration.\u003c/p\u003e \u003cp\u003eSoil physicochemical properties are the main factors affecting the soil infiltration process. Specifically, reduced soil porosity leads to decreased infiltration rate (Hussain et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Soil texture, bulk density, and soil aggregation also significantly affect soil moisture infiltration (Jeffery et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Lim et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The experiment demonstrates that adding drilling mud can effectively delay the infiltration rate of clean water into the soil. This is because the mud particles are very fine, mostly clay, and the solid micro-particles in the drilling mud fill the voids, hindering water infiltration. Additionally, the swelling of polymers and intermolecular bonding also restrict the sample's infiltration.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe M4 group exhibited the best water retention performance. This indicates that as the proportion of drilling mud increases, the water retention performance of the soil improves significantly. This is because, as the ratio of drilling mud to sand increases, the free water in the sand is enhanced by molecular interactions, adsorption, and bonding. Moreover, drilling mud contains a significant amount of clay particles, which promote cohesion between sand particles. Therefore, with an increasing ratio of drilling mud, water retention performance also improves. Hydrophilic polymers, such as polyacrylamide, which act as water-holding agents during drilling, have been proven to increase soil water retention (Geesing \u0026amp; Schmidhalter, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2004\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe addition of small-sized mud particles between large soil particles acts as a bridging agent after compaction and infiltration, altering the soil pore structure. This not only increases soil permeability but also enhances the overall water absorption capacity of large and small particles, leading to improved overall water retention performance. Specifically, the fine particles or clay in the drilling mud fill the larger pores in the sandy soil, causing pore blockage (Bagarello et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Castellini et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Herath et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Soil pore blockage ultimately results in increased water retention. Further comparative analysis reveals that changes in soil water retention are consistent with changes in soil permeability and particle size distribution, though the peak positions differ. This indicates that the particle size distribution of the soil affects changes in water retention. This result is similar to previous findings that drilling mud can help sandy soil form a better structure, increase soil moisture infiltration, and enhance soil water storage (Zvomuya et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2009b\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eThe experiment showed that the addition of drilling mud and cake improved various soil properties. Soil pH increased from 6.51 (CK) to 6.85 (M4), indicating a neutral change without salinization. EC values in M1, M2, and M3 were higher than CK, but decreased with increasing mud amount. Soil organic matter (SOM) and organic carbon (TOC) increased with mud application, with SOM rising from 6.23 g\u0026middot;kg^\u003csup\u003e-1\u003c/sup\u003e (CK) to 19.32 g\u0026middot;kg^\u003csup\u003e-1\u003c/sup\u003e (M4). CEC in M3 reached 12.94 cmol\u0026middot;kg^\u003csup\u003e-1\u003c/sup\u003e, 2.79 times higher than CK. Available phosphorus was highest in M2 (339.01 mg\u0026middot;kg^\u003csup\u003e-1\u003c/sup\u003e), while readily available potassium was highest in M3 (187.35 mg\u0026middot;kg^\u003csup\u003e-1\u003c/sup\u003e). Total nitrogen content increased with mud amount.The total amount of heavy metals in the soil increased with the application of drilling mud and cake. According to the \"Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard\" (GB15618-2018), the risk of heavy metal pollution in the agricultural soil did not reach the threshold.\u003c/p\u003e \u003cp\u003eThe water holding and retention properties of the mixed soil exhibited significant differences under various amounts of drilling mud and cake. The infiltration rate decreased over time and eventually stabilized. The trend of infiltration rate was similar across different amounts, but the infiltration rate in the drilling mud-treated soils was significantly lower than in the sandy soil control group. This is primarily due to the alteration of the soil structure by the drilling mud, which causes the fine particles to reaggregate into larger aggregates, thereby reducing water infiltration. The infiltration rate ranking for different treatments was CK\u0026thinsp;\u0026gt;\u0026thinsp;M2\u0026thinsp;\u0026gt;\u0026thinsp;M1\u0026thinsp;\u0026gt;\u0026thinsp;MC1\u0026thinsp;\u0026gt;\u0026thinsp;M3\u0026thinsp;\u0026gt;\u0026thinsp;MC2\u0026thinsp;\u0026gt;\u0026thinsp;M4, indicating that the addition of drilling mud and cake significantly reduced the infiltration rate.The water retention performance of the soil increased with the amount of drilling mud applied. Compared to the CK group, most treatment groups showed improved water retention performance, with the M4 group exhibiting the best performance. The fine particles in the drilling mud filled the larger pores in the sandy soil, enhancing the overall water retention capacity. This improvement is closely related to the hydrophilic polymers in the mud, such as polyacrylamide, which help enhance soil water retention.\u003c/p\u003e \u003cp\u003eOverall, the application of drilling mud not only improved the particle size distribution of sandy soil but also effectively enhanced the soil's water retention capability. However, excessive water retention might lead to poor plant growth, so the proportion of drilling mud should be adjusted based on the actual needs to achieve optimal soil stabilization results.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflicts of Interest:\u003c/h2\u003e \u003cp\u003eThe authors declare no conflicts of interest.\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eThe authors gratefully acknowledge the financial support provided by the National Key Research and Development Program of China (Grant No. 2021YFC1808902), Agricultural Science and Technology Innovation Project of Shaanxi Province (Grant No. NYJK-2022-XA-02) and Key Research and Development Program of Shaanxi Province (Grant No. 2019NY-200; 2020ZDLNY06-06; 2020ZDLNY07-10), Northwest University Graduate Innovation Project (Grant No. 363052204001).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, Yiliang Liu and Xing Zhang; methodology, Yiliang Liu, Jie Yu, and Xing Zhang; software, Yiliang Liu; validation, Xiaoli Zhu, Ziye Zhang, and Jie Yu; formal analysis, Yiliang Liu and Jie Yu; investigation, Yiliang Liu and Xing Zhang; resources, Yiliang Liu and Shi Zhou; data curation, Shi Zhou; writing\u0026mdash;original draft preparation, Yiliang Liu and Xing Zhang; writing\u0026mdash;review and editing, Xing Zhang; visualization, Xiaoli Zhu; supervision, Shi Zhou; funding acquisition, Xiaoli Zhu. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAbd El Halim AA , Lennartz B (2017) Amendment with sugarcane pith improves the hydrophysical characteristics of saline‐sodic soil. European Journal of Soil Science 68: 327-335.\u003c/li\u003e\n\u003cli\u003eBagarello V, Castellini M , Iovino M (2007) Comparison of unconfined and confined unsaturated hydraulic conductivity. Geoderma 137: 394-400.\u003c/li\u003e\n\u003cli\u003eBall AS, Stewart RJ , Schliephake K (2012) A review of the current options for the treatment and safe disposal of drill cuttings. Waste Management \u0026amp; Research: The Journal for a Sustainable Circular Economy 30: 457-473.\u003c/li\u003e\n\u003cli\u003eBauder TA, Barbarick KA, Ippolito JA, Shanahan JF , Ayers PD (2005) Soil properties affecting wheat yields following drilling-fluid application. 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Soil Science Society of America Journal 72: 1217-1225.\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":"Drilling Mud, Desertified Soil, Soil Improvement, Soil Fertility","lastPublishedDoi":"10.21203/rs.3.rs-5106537/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5106537/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDrilling mud, composed of clay, bentonite, and potassium humate, can enhance nutrient availability in barren, coarse-textured soils. This study examines drilling mud from a coalfield and adjacent wind-sand land, focusing on its microscopic structure, particle size distribution, heavy metal content, and potential for resource utilization.The analysis reveals that the drilling mud is a solid-liquid mixture with a pH of 6.94 and 68.44% water content. The fine precipitated particles have a smooth surface. Adding drilling mud did not significantly affect soil pH or electrical conductivity, nor did it alter salinization or alkalization levels. However, soil organic matter, total nitrogen, available phosphorus, and rapid-release potassium increased significantly. Total heavy metal levels remained within acceptable limits as per the \"Soil Environmental Quality - Risk Control Standard for Soil Pollution of Agricultural Land\" (GB15618-2018).The particle size distribution of the mud spans a few micrometers to several hundred micrometers, effectively filling small sandy soil pores and improving particle size distribution. Adding 30% drilling mud significantly reduced medium and fine sand content while increasing clay and silt from 2.5% (CK group) to 12.8% (M3 group), enhancing soil structure and stability. Water retention in sandy soil improved significantly, with the M4 group achieving 20.5% retention compared to 12.3% in the CK group, demonstrating remarkable enhancement.\u003c/p\u003e","manuscriptTitle":"Feasibility on the Reuse of Waste Drilling Mud for the Treatment of Desertified Soils","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-08 06:39:05","doi":"10.21203/rs.3.rs-5106537/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":"ca31c62e-44a7-4f7c-aa29-fd5d7ccb1dc5","owner":[],"postedDate":"November 8th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-12-03T05:08:10+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-08 06:39:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5106537","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5106537","identity":"rs-5106537","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}