Study of manganese traces in fluvial sediments along the Lluta riverbanks in the Arica and Parinacota region, northern Chile: Archaeological and current implications

Study of manganese traces in fluvial sediments along the Lluta riverbanks in the Arica and Parinacota region, northern Chile: Archaeological and current implications | 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 Study of manganese traces in fluvial sediments along the Lluta riverbanks in the Arica and Parinacota region, northern Chile: Archaeological and current implications Leonardo Figueroa, Bernardo Arriaza, Arnoldo Vizcarra, John Van Hoesen, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4253081/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 The ancient coastal populations of northern Chile called Chinchorro used manganese (Mn) oxide extensively for the preparation and ornamentation of their deceased. The possible sources of extraction of this mineral have been debated in several studies. This work focuses on the study of dry sediments from the Lluta riverbed in the Arica y Parinacota region to characterize Mn concentrations in alluvially transported material at different points along the river. Six riverbed sediment samples were collected from an altitude of 1,328 masl to 6 masl. The samples were sieved into five-size fractions and Mn concentrations were measured using atomic absorption spectroscopy. It was found that Mn concentrations vary inversely proportional to altitude with a correlation coefficient of -0.91. The highest Mn levels are found in samples near the coast with the following values: total water-soluble Mn 243 µg/g, total exchangeable Mn 248 µg/g, and total acid-soluble Mn 4,607 µg/g. These levels of Mn would not correspond to a primary or important source for the extraction of black Mn ore by the archaic inhabitants for mortuary preparation of the Chinchorro mummies. Nevertheless, the presence of Mn in the riverbed raises questions about the health consequences for the ancient populations and the importance of monitoring Mn in the water due to possible bioaccumulation of this mineral in agricultural products of the area. Manganese traces Chinchorro Riverbanks Mineral Arica y Parinacota Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction The Lluta River in the extreme northern of Chile, bisects the Atacama Desert and brings water from the highlands to the lowlands. At the highland’s headwaters, large manganese (Mn) mantles particularly within the Lauca and Huaylas Formations are present (Ossa, 1970 ; Van Hoesen et al., 2018 ). These Mn oxide-rich geological mantles are of significant socioeconomic interest from a mining point of view. In addition, the ancient Chinchorro people, the earliest settlers of the Atacama regions, traveled to the highlands to acquire Mn from these Formations and they were the main source of minerals used in their complex preparation of their deceased (Arriaza, 1995 ; Guillen, 1997 ; Sepúlveda et al., 2013 ; Standen, 1997 ). For example, the well-documented preparation of the so called, black and red mummies (Arriaza & Standen, 2016 ; Arriaza et al., 2023a , b ; Sepúlveda et al., 2013 ). Arriaza et al., 2023b recently proposed that due to heavy highland rains and steep slopes where the mantles are found, Mn rocks break down easily and in turn, reach the lowlands and form part of the river terraces. Along these lowland terraces, Chinchorro people could have extracted the Mn for use in the mortuary context described (Arriaza & Standen, 2016 ; Arriaza et al., 2023a , b ; Ossa, 1970 ; Sepúlveda et al., 2013 ; Van Hoesen et al., 2018 ). This Mn integration in the Lluta River ecosystem highlights not only the geological and landscape dynamics but also a profound cultural significance of the natural resources, linking the Lluta River to the Chinchorro's artistic and mortuary expressions. This work describes Mn levels present in the current sediments of the Lluta River to test the solubilization processes. Sediments from the Lluta riverbed at various elevations were sampled for the quantification of Mn, considering water-soluble, exchangeable forms, and acid-soluble forms in the sediment. We focused on the possible Mn sources available to the ancient archaic populations of northern Chile and its potential effects upon modern populations. 1.1 Local water processes and Mn mobility The heavy rains in the Andean Chilean highlands (January-February) contribute to physical and chemical weathering of the soil and native minerals. The natural weather phenomena occurring in the highlands and in the Lluta River basin are visible during the rainy season, where for example during February 2019, the river changed from an annual average flow of 3.01 m 3 /s to 19.53 m 3 /s ( https://snia.mop.gob.cl/BNAConsultas/reportes ). The colluvial and alluvial processes along the river facilitate the transportation of weathered material such as rocks, small stones, gravel, and fine sediments to lower elevations along the Lluta River. These materials undergo physical and chemical weathering according to seasonal water fluctuations, which results in a reduction of particle size for Mn-rich materials that are eventually deposited along the river. The resulting smaller particles possess a larger surface area, which facilitates chemical reactions within the aqueous solution of the Lluta River, transforming the Mn oxide into free Mn 2+ cations. Increased acidity in the Lluta River is produced by the Azufre River contribution, one of the tributaries at the Lluta River headwaters (ca. 3,982 meters above sea level or masl). This facilitates ionic speciation and interactions with the sediments depending on the pH of the water (Zumaeta, 1981 ). 1.2 The produced ionic Mn The Mn cation is an ionic chemical species, which becomes part of the solutes dissolved in the water of the river and can also be reactive with undissolved sediment. The Lluta River sediment is made up of sand, silt, clay, and various oxides-hydroxides that are deposited on the bank and riverbed after flooding. The Mn cation can interact with clay minerals through ion exchange reactions and can be transported by the river in times of flooding. These processes led to the formation of various ionic forms of Mn in the dry river deposits located on the banks of the Lluta River after the rainy seasons. 1.3 The different quantifiable forms of Mn To quantify the Mn present in the sediments we used three approaches: Water-soluble form: concentration of Mn in the sediment released by the action of water through the phenomenon of solubilization and hydrolysis. Exchangeable form: the Mn in the sediment retained by physical adsorption in the cation exchange complex and released by reaction with the aqueous solution of the potassium cation. Acid soluble form: the Mn in the sediment typical of oxide and oxide-hydroxide type minerals of the element. 1.4 Conductivity and pH In the study of sedimentary processes, the behavior of mineral components plays a crucial role the chemical and physical weathering of minerals resulting in the water-soluble fraction of Mn in the sediment, comprising inorganic and ionic salts. This fraction, when interacting with water, dissolves various saline species, thereby imparting electrolytic properties to the solution, as evidenced by electrical conductivity measurements. These interactions can also trigger hydrolysis reactions, altering the pH of the aqueous system. An acidic pH increases the likelihood of dissolving oxide-type components, including Mn oxides, contributing further to the water-soluble form of Mn. This study considers the sediment fractions, differentiated by particle size and by the weighted concentration of the total Mn transported in the fractions, at known location along the river. 1.5 Overall considerations The quantification of Mn concentrated in river sediments has archaeological implications. Its quantification allow us to determine whether the riverbed sediments have enough Mn in oxide form that could have been used by the Chinchorro populations to decorate their dead. It also provides new data to debate the potential toxicity that these sediments could have had on the health of the population that used this material. This is highly relevant considering overexposure to high Mn concentrations has toxic effects on humans (Arriaza & Galaz-Mandakovic, 2022 ; ATSDR, 2012; Guerra et al., 2016 ; Lucchini et al., 2015 ; Mena et al., 1967 ; O’Neal & Zheng, 2015 ; Ramírez y Ayala, & Azcona-Cruz (2017). The study of Mn in river sediment has current health importance (e.g., environmental contamination). 2. Materials and methods 2.1 Collection of sediment samples Dry sediment samples were collected from six different areas along the Lluta River after eight (8) months of the highland season rainfall. Before sampling the area, the characteristics of the riverbed were visually examined, looking for dry sediment banks visible to the naked eye. The sediment sought was characterized by the presence of clays and well-defined deposits. About 2 kg of soil per sample was collected at each area, using a plastic shovel cleaned with distilled water before collecting the next sample. Soil samples were collected in polyethylene bags. Each sample was assigned an identification code based on its extraction area, dated, and labeled including its GPS location and altitude, using a Garmin GPSMAP 62s Series (Fig. 1 and Table 1 ). Samples were transported to the Universidad de Tarapacá Chemical Laboratory for analysis. The sediment sample gathering was undertaken from higher to lower altitudes. Consequently, in the text, the terms 'area', 'zone', and 'sediment number' refer to the same sample and are used interchangeably. Table 1 Location of the sample collected along the Lluta riverbed. Sediment sample (Zone) masl UTM, grid zone 19K X (East) Y (North) 1 1,328 412495 7973598 2 1,124 406480 7969826 3 872 397732 7966086 4 527 386800 7959487 5 23 361963 7964444 6 6 360255 7963591 2.2 Treatment of the soil samples Sieving of the soil samples Each sediment sample was manually pulverized using a porcelain mortar, avoiding generation of high pressure to causes crystalline breakage. The resulting material was then fractionated using a stainless steel sieve model Retsch AS 200 digit CA, with five different mesh aperture sizes, ≤ 1,000 µm (coarse sand); ≤500 µm (medium sand); ≤250 µm (fine sand); ≤90 µm (very fine sand); and ≤ 63 µm (very fine sand, silt and clay). Following sediment separation, each fraction was packed into a plastic bag and labeled for subsequent analysis. Chemical treatment and analysis of the sediment fractions a) Water-soluble form (Mn, conductivity, and pH): 50 mL of distilled water (Electrical Conductivity - EC ≤ 3 µS/cm) was added to 20.00 g mass of the corresponding sediment fraction to get a 2.5 weight/volume ratio. The solution was placed in a 100 mL wide-mouth polypropylene bottle with a screw cap and properly labeled. The container was hermetically sealed and shaken orbitally for two hours at 250 rpm. After hydrolysis reactions between the reactive phases in the solubilization reached equilibrium, the flask was shaken manually to homogenize the aqueous mixture. Then electrical conductivity and pH were measured in the suspension of the sediment in water for each of the samples, using a conductivity meter calibrated with 0.01M KCl solution and a pH meter previously calibrated at pH 4 and 7. After the pH measurements were completed, the aqueous mixture of the sediment was filtered through Whatman 2 qualitative paper and packed in a hermetically sealed polypropylene bottle. The Mn concentration was quantified using this aqueous solution. b) Exchangeable form: The treatment of the sediment to quantify its exchangeable form was carried out in a similar way to the treatment of the water-soluble form, except that the reagent solution with the sediment was KCl of 1M concentration adjusted to pH 7.0. The Mn concentration was quantified in the respective filtrate of the potassium solution. c) Acid soluble form: A mass of 0.5 ± 1*10 − 4 g of the sediment sample and its respective fractions were weighed and placed in a beaker. 10 mL of 6M hydrochloric acid (HCl) A.C.S. was added to the beaker. The mixture was heated under a fume hood in a semi-closed system with constant stirring on a hot plate, bringing it to a boil until the volume was reduced by half. After room temperature cooling (20–25 o C), 25 mL of distilled water was added to ensure solubility, while monitoring the temperature. Once complete solubilization of the ionic forms was achieved at room temperature, the mixture was quantitatively transferred to a 100 mL volumetric flask and made up to volume with distilled water. The decanted solid phase mixture was filtered through qualitative Whatman 2 paper, and the filtrate was placed in a polypropylene container with a tight-fitting lid. The total concentration of Mn was quantified using this acid solution. The respective Mn concentrations of the water-soluble and exchangeable forms were subtracted from this concentration to obtain the Mn concentration corresponding to the acid-soluble form. 2.3 Quantification of manganese The Mn analyte contained in each of the solutions obtained from the different extraction methods was quantified using Atomic Absorption Spectroscopy, Agilent Technologies FSAA 240, with the following operating parameters: Hollow Cathode Lamp: Mn; PROMT (Precision Optimized Measurement Time) measurement system; Flame Type: Air- Acetylene (oxidant); Measurement replicates: 3 for calibration standard and sample; Read delay time: 2 seconds; Measurement time: 2 seconds; Wavelength: 279.5 nm; Slit width: 0.2 nm; Background correction: On (Deuterium-D 2 lamp); Calibration range in the aqueous matrix, KCl matrix and HCl matrix: 1 to 6 mg/L; Calibration algorithm: New rational, providing a rational best-fit line in the absorbance versus concentration domain; Calibration curve: Concentration = (a *Absorbance2) + (b * Absorbance) + c; Characteristic concentration: 0.045 mg/L; Correlation coefficient (r): 1; Limit of Detection (LOD), sd*3, for linear zero-intercept curve: 0.014 mg/L. 2.4 Statistical analyses The data was analyzed using Excel, SPSSV25, and Statgraphics V18. Graphs and a Spearman correlation were undertaken (non-parametric samples). A Shapiro-Wilk normality, Krukall-Wallis, and Games-Howell post Hoc analyses for non-parametric data were undertaken. 3. Results and discussion 3.1 Particle size of the sediment The results in Table 2 show that all five size fractions are present in each of the sediments analyzed. There is a tendency for the highest percentages of mass distribution to be found in the smallest size fraction of the sediment. The particle size in the collected sediment may be variable to some degree depending on the Mn forms. For example, the exchangeable Mn is assumed to interact with the clay fraction which facilitates the adsorption of the Mn 2+ cation through the simple attraction of charges, resulting in non-specific and exchangeable physical adsorption. Table 2 Percentage distribution of the mass of each sediment fraction according to the sampling zones. Sediment Percent of fraction in the sediment according to zone sampled Average (Fraction) Sediment category Fraction µm 1 2 3 4 5 6 ≤ 1000 4.70 10.00 14.30 14.80 2.80 18.50 10.85 Coarse sand ≤ 500 14.40 11.10 15.70 14.30 2.20 12.60 11.72 Medium sand ≤ 250 35.40 22.40 21.50 16.60 10.20 20.10 21.03 Fine sand ≤ 90 15.20 11.10 13.60 8.20 9.50 12.70 11.72 Very fine sand ≤ 63 30.20 45.40 35.00 46.10 75.20 36.20 44.68 Very fine sand, silt and clay Total 99.9 100 100.1 100 99.9 99.9 100 - Figure 2 displays the average percentage distribution of each fraction across six sediment samples. In the ≤ 63 µm fraction, consisting of very fine sand, silt, and clay, we found that the highest average percentage of total Mn material is 44.68%. This increased to 56.40% when considering the ≤ 90 µm fraction of very fine sand and reached up to 77.43% with the inclusion of the ≤ 250 µm fraction corresponding to fine sand. In general, the data showed a physical weathering of the larger particles entering the riverbed resulting in smaller particles at the lowlands (Table 3 , Zones 5 y 6). 3.2 Electric conductivity The electrical conductivity values in Table 3 reveal the significantly elevated presence of ionic activity in the aqueous solution of the overall sediment pool, including water-solubilized Mn. Table 3 Electrical conductivity of the water-solubilized sediment solution. Sediment EC µS/cm in sediment-water according to the zone sampled Average Fraction EC Fraction / µm 1 2 3 4 5 6 ≤ 1000 2,790 5,280 6,750 786 5,520 7,460 4,764.33 ≤ 500 1,849 4,950 8,240 720 5,160 4,900 4,303.17 ≤ 250 853 4,790 10,200 1,217 4,090 7,380 4,755.00 ≤ 90 866 4,200 10,550 1,694 2,170 6,990 4,411.67 ≤ 63 1,187 4,050 9,600 1,618 2,070 5,760 4,047.5 Average 1,509 4,654 9,068 1,207 3,802 6.498 4,456.33 S. D. 822.20 516.94 1,566.80 452.93 1,623.41 1,122.91 1,017.53 3.3 pH pH data from sediments collected at different zones of the Lluta River (Table 4 ) showed a gradient from low acidity to slight alkalinity (pH 6.1–7.9), with a general decrease in pH in finer fractions (≤ 90 µm and ≤ 63 µm), particularly in lower elevation zones 5 and 6. This pattern indicated a higher acidification influence in fine particles. The coarser fractions exhibited a higher pH, potentially reflecting their chemical stability and lower reactivity. These pH variations by particle size and zone may suggest differences in the source and nature of the sedimentary material, with potential implications for the mobility of Mn cations. Table 4 pH values in sediment water. Sediment Fraction / µm pH in sediment water according to zone sampled Average fraction pH 1 2 3 4 5 6 ≤ 1000 7.5 7.0 7.7 7.6 6.8 6.9 7.25 ≤ 500 7.6 7.3 7.7 7,5 6.8 7.0 7.32 ≤ 250 7.8 7.1 7.5 7.3 6.9 6.5 7.18 ≤ 90 7.9 7.0 7.5 7.3 7.3 6.1 7.18 ≤ 63 7.8 6.9 7.4 7.3 7.3 6.4 7.18 Average 7.7 7.1 7.6 7.4 7.0 6.6 7.23 S.D. 0.16 0.15 0.13 0.14 0.26 0.37 0.20 a) Water-soluble form The results shown in Table 5 correspond to the concentration of Mn in its water-soluble form, i.e. the Mn element is present in all the fractions (Average sediment 0.18–48.68 µg/g). Although the Mn element is present in all the fractions, in Zone 1 (1,328 masl) its concentration is practically extremely low or undetectable in each of the fractions. In contrast, the maximum concentrations of Mn revealed among all fractions tend to be present in Zone 6 with of maximum of 74.5 µg/g in the ≤ 90 µm fraction. Table 5 Water soluble Mn concentration. Sediment Fraction µm Mn µg/g sediment according to zone sampled Average Mn fraction 1 2 3 4 5 6 ≤ 1000 0.8 7.2 7.3 1.0 51.5 34.9 17.12 ≤ 500 0.0 4.7 9.9 1.0 60.1 46.7 20.40 ≤ 250 0.1 7.6 15.3 3.0 27.1 62.5 19.27 ≤ 90 0.0 8.1 14.7 4.2 9.2 74.5 18.45 ≤ 63 0.0 7.2 12.9 2.6 6.0 24.8 8.92 Total 0.9 34.8 60.1 11.8 15.9 243.4 61.15 Average 0.18 6.96 12.02 2.36 30.78 48.68 16.83 S.D. 0.35 1.32 3.37 1.37 24.40 20.14 4.58 This tendency of greater concentration of Mn in the lowlands aligned with the fluvial transport dynamics and suggested an increased potential for Mn bioaccumulation in the sediment matrix towards the river's mouth. Thus, at some point in the river, the larger clasts are broken down to a fine fraction that is carried to the mouth of the river. This finding is also significant for environmental impact studies and water resource management considering that large agriculture fields are present in the lowlands. b) Exchangeable form Table 6 shows the clay particles have more Mn in lower elevation areas (Zones 5 and 6) and Mn particles were effectively transported as non-dissolved solids in the river water flow. The desorption or cation exchange phenomenon occurred about the availability of Mn in the aqueous matrix and its cationic form Mn 2+ which can be subsequently assimilated by plant organisms. Table 6 Exchangeable Mn concentration. Sediment Mn µg/g sediment according to zone sampled Average Mn fraction Fraction µm 1 2 3 4 5 6 ≤ 1000 0.48 9.4 3.9 8.8 46.1 30.3 16.50 ≤ 500 0.30 2.6 2.4 6.0 20.3 76.7 18.05 ≤ 250 0.15 1.8 4.4 4.2 4.9 57.9 12.23 ≤ 90 0.21 2.8 8.1 6.1 10.7 52.9 13.47 ≤ 63 0.25 1.1 3.8 6.6 14.0 29.7 9.24 Total 1.39 26.7 22.6 31.7 96.0 247.5 70.98 Average 0.28 3.54 4.52 6.34 19.20 49.50 13.90 S.D. 0.13 3.34 2.13 1.65 16.04 19.89 7.20 The concentration of exchangeable Mn varies according to the zone in sediments. For all the Zones, the highest concentration of Mn was found in Zone 6 with 76.7 µg/g. This finding is comparable to that of Mn in its soluble form. c) Acid soluble form Table 7 indicates that there is significant spatial variability in the concentration of acid-soluble Mn within the sediments from different zones along the Lluta River. Zones 5 and 6 showed the highest total concentrations suggested either a localized source of Mn or less effective dilution and transport by the river system in these areas. Notably, the smallest particle size (≤ 63 µm) in Zone 3 contains the highest single concentration of Mn, which is consistent with the understanding that finer particles can have higher metal concentrations due to their larger surface area to volume ratio. Table 7 Acid soluble Mn concentration. Sediment Mn µg/g sediment according to zone sampled Average Mn fraction Fraction µm 1 2 3 4 5 6 ≤ 1000 309 434 315 352 917 973 550.00 ≤ 500 871 408 609 394 964 1.004 708.33 ≤ 250 729 581 708 587 826 944 729.17 ≤ 90 617 640 854 645 670 847 712.17 ≤ 63 642 623 1.114 597 641 839 742.67 Total 3,168 2,686 3,600 2,575 4,018 4,607 3,442.33 Average 633.60 537.20 720.00 515.00 803.60 921.40 688.47 S.D. 206.86 108.62 295.67 132.30 144.38 74.70 160.42 This form of Mn in the sediment represents the phenomenon of physical weathering due to water flow. There is a reduction of the original size of the Mn rock along the riverbed. 3.4 Correlation comparisons Figure 3 shows a matrix correlation between the three Mn extraction methods used and their relationship with electrical conductivity, pH, elevation, and particle size. The Spearman correlation coefficient indicates the strength and direction of the associations. The three Mn extraction methods demonstrate a positive correlation with each other, the strongest being between water-soluble Mn and exchangeable Mn (r = 0.72). This suggests that despite differences in extraction techniques, there is a significant relationship in Mn levels detected by these methods and that extraction techniques do not affect the results. A marked negative correlation (r =-0.91) is observed between elevation and the concentration of available exchangeable Mn, indicating higher availability of exchangeable Mn at lower elevations, especially in coastal areas. Instead, electrical conductivity, shows a low to moderate correlation with Mn extraction methods, indicating that it is not a reliable indicator for predicting the concentration of soluble Mn ions. 3.5 Comparison between Mn extraction methods The water-soluble, exchangeable forms and acid soluble showed a certain tendency for the concentration of Mn in its oxidized species to be higher in the areas closest to the river mouth (Fig. 4 ). In some way, this could be validated by a particle size of Mn oxides small enough in their solid aggregate state to be transported by the fluvial system to a lower elevation and finally deposited with other solid materials of the system's matrix. In addition, the different methods are at a markedly higher ratio, in the order of 19 to 3,090 and 12 to 2,060 times respectively relative to the average values at their statistical maximum and minimum. Comparing the three extraction methods, the acid-soluble Mn form removed a higher concentration of manganese from the sediments. Taking into consideration the weathering processes already described, we can conclude that in all methods the lowlands samples have the highest concentration of Mn. 3.6 Statistical considerations The Shapiro-Wilk normality test indicated that both soluble Mn and exchangeable Mn present a non-parametric distribution (p-value = 0.001), while acid-soluble Mn present a parametric distribution (p-value = 0.332). Considering that two variables (soluble Mn and exchangeable Mn) presented a non-parametric distribution, a Kruskall-Wallis analysis was used, which resulted in a test value of 59.50 and a p-value of 0.001. This statistical test verifies that there are significant differences between the different Mn extraction methods. Thus, the Games-Howell post hoc test for non-parametric data shows a distribution cluster grouping the extraction of soluble Mn and exchangeable Mn as one group (p-value = 0.845) and the acid-soluble Mn into another group (p-value = 0.001). 3.7 Archaeological implications In the past, during different periods, ancient people probably could have accessed Mn highland sources to use in their rock art expressions (Sepúlveda et al., 2013 ) or for the ornamentation of the Chinchorro mummies. Nevertheless, for the Chinchorro it has been recently argued that the Chinchorro populations extracted Mn from the lowlands of Arica (Arriaza et al., 2023b ). According to the various types of chemical analyses, the higher levels of Mn concentration found in the sediments of the Lluta riverbed indicate that coastal populations living near Arica river mouths (e.g. Lluta River) would potentially have a higher level of exposure than populations inhabiting higher elevation floors at different stages of cultural development in the region. Although these Mn concentration levels, in relative terms, are low from the perspective of the raw material available (Mn pigment) not reaching a significant percentage. The overall average of the sediment fractions and zone concentration was less than 0.1%. However, this low concentration could hypothetically have been added to or accumulated in the mineralogical matrix of the Mn pigments used by the ancient Chinchorro populations. The mineral matrix used in the form of paste to ornament the Chinchorro mummies required water for its preparation, a vital element that must have been extracted from the water resources near the coast. 3.8 Human health implications On the other hand, the Chilean standard NCh 409, recommends that the level of Mn in drinking water should not exceed 0.1 mg/L (0.1 ppm), and the NCh 1333 applicable to water for irrigation suggested 0.2 mg/L (0.2 ppm). Nevertheless, the accumulation of Mn in the river sediments and the waters could have created a potential risk for the ancient settlers as well as for the modern ones. Overexposure to Mn either by ingestion of water or by suspended particulate matter is harmful to health (Dey et al., 2023; Lucchini et al., 2015; O’Neal & Zheng, 2015; Riojas-Rodríguez et al., 2010; Solís-Vivanco et al., 2009; Ramírez y Ayala, & Azcona-Cruz, 2017; Tchernitchin et al., 2015; Wu et al., 2022). The latter source of input is more harmful considering the alternative of a probable acute or short-term poisoning phenomenon by inhaling the Mn duct, which mainly affects miners (Mena et al., 1967). Although today the current populations of Arica do not practice Mn mining, agricultural products in the Lluta Valley could hypothetically bioaccumulate Mn from the use of Mn-contaminated irrigation water. Elsewhere scholars have reported Mn in crops (Awino et al., 2021). Average Mn in soil has been reported as 330 mg/kg with a range of 40 to 900 mg/kg (Lucchini et al., 2015). Table 5 on water-soluble Mn shows that river sediments in the geographical zones 3, 5 and 6 have Mn levels higher than the lower range reported in the literature with 60.1; 153.9 and 243.4 µg/g Mn. Conclusion The eventual natural disposition of Mn oxide rocks in the Lluta riverbed, coming from the mineral mantle, can be weathered by both chemical and physical mechanisms. The transport of materials generated by the flow of the river and the sedimentation of these, together with the evaporation of water on the riverbanks, generated solid sediments that present chemical and physical properties revealing the phenomenon of weathering. The presence of both water-soluble and exchangeable forms of Mn revealed a chemical weathering process associated with the Mn oxide ore, and the presence of the acid-soluble form of Mn suggests a physical weathering process of the Mn oxide ore. The higher Mn concentration associated with the size-reduced Mn oxide material compared to the concentration of both water-soluble and exchangeable Mn or the addition of the latter two revealed that physical weathering of the original Mn oxide material is the main process of size reduction of the Mn oxide material. There is increasing fine-grained Mn in lower elevations of the riverbed. However, the total Mn transported and the low concentration of Mn oxide ore, denoted that Lluta riverbed are not a significant source of Mn to be used for mortuary preparation. Certainly, the presence of Mn in the riverbed would be varied according to the magnitude of the alluvial phenomena, the ENSO fluctuations, and the amount of rain affecting the Mn mantles in the highlands. However, the riverbed does not provide enough Mn compared to the river terraces to aid in the preparation of the Chinchorro mummies. Mn in the riverbed sediments and dissolved in its waters could have been eventually ingested by ancient people, whose concentration and effects need to be studied. On the other hand, the waters of the Lluta River are currently used for agriculture so they should be monitored to verify that the availability and absorption of Mn does not present a risk to the current population due to bioaccumulation in the agricultural products irrigated with these waters. Declarations Conflict of interest The authors declare no conflict of interest. Author Contribution Specific Contributions of the AuthorsL.F.: Conceptualization, Methodology, Investigation, Supervision, Resources, Writing – review & editing.B.A.: Conceptualization, Methodology, Investigation, Supervision, Resources, Funding acquisition, Project administration, Writing – review & editing.A.V.: Methodology, Formal analysis, Writing – review & editing.C.C.: Methodology, Laboratory analysis, Writing – review & editing.S.B.: Methodology, Laboratory analysis.J.V.H.: Conceptualization, Writing – review & editing.All authors participated in the manuscript review process. Acknowledgement We thank Fondecyt 1210036 grant for financial support. References Agency for Toxic Substances and Disease Registry (ATSDR), (2012). Toxicological Profile for Manganese . U.S. Department of Health and Human Services, Public Health Service, Atlanta, GA. Arriaza, B. (1995). Beyond Death: The Chinchorro Mummies of Ancient Chile. Smithsonian Press. Arriaza, B., & Galaz-Mandakovic, D. (2022). Manganese mining in Corral Quemado: extractivism processes that resulted in manganese madness among miners (Coquimbo region, Chile, 1941-1969), Labor History , doi: 10.1080/0023656X.2022.2111550 Arriaza, B., & Standen, V. (2016). Catálogo de momias Chinchorro: Cuerpos con momificación artificial. Ediciones Universidad de Tarapacá. Arriaza, B., Ogalde, J.P., Gutiérrez, S., Cárcamo, J., Standen, & V., Figueroa, L. (2023a). Evidencia arqueométrica del uso del manganeso en artefactos asociados a la Cultura Chinchorro. Lat. Am. Antiq . in press. doi:10.1017/laq.2022.102. Arriaza, B., Ogalde, JP., Vizcarra, A., Aravena, N., Standen, V., Figueroa, L., Zelaya, G., Reich, M., Halcrow, S., & Van Hoesen, J. (2023b). To move or not to move? Manganese oxide procurement during the Archaic period in the Atacama Desert. Journal of Archaeological Science: Reports , 51, 104157. Awino, F.B., Maher, W., Lynch, A., Asanga, P.B., & Otim, O. (2021). Comparison of metal bioaccumulation in crop types and consumable parts between two growth periods. Integrated Environmental Assessment and Management , 18, 1056-1071. Dey, S., Tripathy, B., Kumar, M.S., Das, A.P. (2023). Ecotoxicological consequences of manganese mining pollutants and their biological remediation. Enviro. Chemistry and Ecotoxicology., 5, 55-61 (2023). Guerra, P., González, C., Escauriaza, C., Pizarro, G., & Pasten, P. (2016). Incomplete Mixing in the Fate and Transport of Arsenic at a River Affected by Acid Drainage. Water Air Soil Pollut , 227(3). Guillen, S. (1997). Morro 1-5 (Arica). Momias y sociedades complejas del Arcaico de los Andes Centrales. Boletín de Arqueología PUCP, 1, 65-78. Lucchini, R., Aschner, M., Kim, Y., & Saric, M (2015). Manganese in G.F. Nordberg, B.A. Fowler, M. Nordberg, (Eds.), Handbook on Toxicology of Metals (4th ed., pp. 975-1005). Academic Press. Mena, I., Marin, O., Fuenzalida, S., Cotzias, G. (1967). Chronic manganese poisoning. Clinical picture and manganese turnover. Neurology, 17, 128-136. O’Neal, S. & Zheng, W. (2015). Manganese toxicity upon overexposure: A decade in review. Curr. Environ. Health Rep ., 2, 315-328. Ossa, A.C. (1970). Genesis of manganese deposits in Northern Chile. Economic Geology and the Bulletin of the Society of Economic Geologists ,65 (6), 681-689. doi: 10.2113/gsecongeo.65.6.681. Ramírez y Ayala, R., & Azcona-Cruz, M.I. (2017). Efectos tóxicos del manganeso. Revista de especialidades médico-quirúrgicas 22, 71-75. Riojas-Rodríguez, H., Solís-Vivanco, R., Schilmann, A., Montes, S., Rodríguez, S., Ríos, C., & Rodríguez, A. (2010). Intellectual function in Mexican children living in a mining area and environmentally exposed to manganese. Environ. Health. Perspect., 118, 1465-1470. Sepúlveda, M., Valenzuela, D., Cornejo, L., Lienqueo, H., & Rousselière, H. (2013). Óxidos de manganeso en el extremo norte de chile: abastecimiento, producción y movilidad del color negro durante el período arcaico. Chungará, 45(1), 143-159. Solís-Vivanco, R., Rodríguez-Agudeloa, Y., Riojas-Rodríguez, H., Ríos, C., Rosas, I., & Montes, S. (2009). Cognitive impairment in an adult Mexican population non-occupationally exposed to manganese. Environ. Toxicol. Pharmacol ., 28, 172-178. Standen, V. (1997).Temprana complejidad funeraria de la cultura Chinchorro: norte de Chile. Latin American Antiquity, 8, 134-156. Tchernitchin, A., Ríos, J., Cortés, I., & Gaete, L. (2015). Polimetales en agua de Arica-Parinacota: Posibles orígenes y efectos en la salud. Congreso Geológico Chileno XIV . La Serena, pp. 296-299. Van Hoesen, J., Arriaza, B., Ryan, P., & Grady, C. (2018). A multianalytical approach for identifying a manganese source for the black pigment of the Chinchorro mortuary palette. Geoarchaeology, 34, 322-335. Wu, R., Yao, F., Li, X., Shi, C., Zang, X., Shu, X., Liu, H., & Zhang, W. (2022). Manganese Pollution and Its Remediation: A Review of Biological Removal and Promising Combination Strategies. Microorganisms , 10, 2411. Zumaeta, D. (1981). Constituyentes químicos en varias aguas de riego de las provincias de Arica y Parinacota, Primera Región - Chile. Revista Arica, Serie Química, Universidad del Norte, 1327-169. 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-4253081","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":291057232,"identity":"b90d144f-1747-4ab0-966e-1444f1b1db39","order_by":0,"name":"Leonardo Figueroa","email":"","orcid":"","institution":"University of Tarapacá","correspondingAuthor":false,"prefix":"","firstName":"Leonardo","middleName":"","lastName":"Figueroa","suffix":""},{"id":291057233,"identity":"51961f48-4228-4e72-8a4e-e1b3c76a7357","order_by":1,"name":"Bernardo Arriaza","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA80lEQVRIiWNgGAWjYBACAxCRAGYyNjAwVABpZuYGUrScAWlhJEILHDC2wfTiAebsZ599eFBTJ88/+3Djh5/zaqP524FaflRsw6nFsifdeEbCMTbDGecSmyV7tx3PnXGYsYGx58xt3A47kMbMkMDGw9hwBugq3m3HchuAWpgZ2/BoOf8MqOWfhP18oBbGv3OO5c4nqOUG0JbENoPEDUAtzLwNNbkbCGmxnAG0JbEvIXnjGcZmaZljB3I3ArUcxOcXc/40ZsYf3+ps551hf/jxTU1d7rzzhw8++FGBWws6OAwmDxCtHgjqSFE8CkbBKBgFIwQAADp/WveyvQEpAAAAAElFTkSuQmCC","orcid":"","institution":"University of Tarapacá","correspondingAuthor":true,"prefix":"","firstName":"Bernardo","middleName":"","lastName":"Arriaza","suffix":""},{"id":291057234,"identity":"0ad5c8c8-c0e8-4222-901e-dc79f837e1b9","order_by":2,"name":"Arnoldo Vizcarra","email":"","orcid":"","institution":"University of Tarapacá","correspondingAuthor":false,"prefix":"","firstName":"Arnoldo","middleName":"","lastName":"Vizcarra","suffix":""},{"id":291057235,"identity":"845150af-8f8c-417f-9a8a-ad097a411c30","order_by":3,"name":"John Van Hoesen","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"John","middleName":"Van","lastName":"Hoesen","suffix":""},{"id":291057236,"identity":"7ff0daaa-af63-46e7-8865-124674903489","order_by":4,"name":"Stephanie Bustamante","email":"","orcid":"","institution":"University of Tarapacá","correspondingAuthor":false,"prefix":"","firstName":"Stephanie","middleName":"","lastName":"Bustamante","suffix":""},{"id":291057237,"identity":"0bcb9003-a79e-4c17-becd-6c1357bed408","order_by":5,"name":"Camila Contreras","email":"","orcid":"","institution":"University of Tarapacá","correspondingAuthor":false,"prefix":"","firstName":"Camila","middleName":"","lastName":"Contreras","suffix":""}],"badges":[],"createdAt":"2024-04-11 14:35:04","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4253081/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4253081/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":54869398,"identity":"cf1c2867-5ebd-4649-b9b8-b716b516da76","added_by":"auto","created_at":"2024-04-18 00:01:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":5191689,"visible":true,"origin":"","legend":"\u003cp\u003eSediment samples collected along the Lluta River; all samples were taken from dry riverbed soil\u003c/p\u003e","description":"","filename":"Fig.1.png","url":"https://assets-eu.researchsquare.com/files/rs-4253081/v1/1b1b788c1c48e60ae8178b4f.png"},{"id":54869395,"identity":"da107dcb-8547-4894-91bd-8f6317428916","added_by":"auto","created_at":"2024-04-18 00:01:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":270278,"visible":true,"origin":"","legend":"\u003cp\u003ePercentage distribution trend of particle size based on the average sieve of six sediment samples\u003c/p\u003e","description":"","filename":"Fig.2.png","url":"https://assets-eu.researchsquare.com/files/rs-4253081/v1/56436c44a132d173b6245597.png"},{"id":54869460,"identity":"c30323f5-5021-4bd2-adba-a3965cca500c","added_by":"auto","created_at":"2024-04-18 00:09:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":308005,"visible":true,"origin":"","legend":"\u003cp\u003eHeat map summary of Spearman correlation coefficient between Mn extraction methods and other environmental parameters\u003c/p\u003e","description":"","filename":"Fig.3.png","url":"https://assets-eu.researchsquare.com/files/rs-4253081/v1/6b01cdb0088f4021ae172b90.png"},{"id":54869396,"identity":"997ec66c-122d-425c-91bb-f1fd76e924fb","added_by":"auto","created_at":"2024-04-18 00:01:07","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":638131,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of Mn types based on the average fractions between six sediment samples. a) Distribution trend of water-soluble Mn. b) Distribution trend of exchangeable Mn. c) Distribution trend of acid-soluble Mn\u003c/p\u003e","description":"","filename":"Fig.4.png","url":"https://assets-eu.researchsquare.com/files/rs-4253081/v1/7cf8747f404e960b150f8443.png"},{"id":55265058,"identity":"9a67f141-0644-4e09-9d55-2d5cacbb4fb5","added_by":"auto","created_at":"2024-04-25 01:54:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3271119,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4253081/v1/d08d43c1-cb27-4dfe-aa0a-510ba9162429.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Study of manganese traces in fluvial sediments along the Lluta riverbanks in the Arica and Parinacota region, northern Chile: Archaeological and current implications","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe Lluta River in the extreme northern of Chile, bisects the Atacama Desert and brings water from the highlands to the lowlands. At the highland\u0026rsquo;s headwaters, large manganese (Mn) mantles particularly within the Lauca and Huaylas Formations are present (Ossa, \u003cspan class=\"CitationRef\"\u003e1970\u003c/span\u003e; Van Hoesen et al., \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). These Mn oxide-rich geological mantles are of significant socioeconomic interest from a mining point of view. In addition, the ancient Chinchorro people, the earliest settlers of the Atacama regions, traveled to the highlands to acquire Mn from these Formations and they were the main source of minerals used in their complex preparation of their deceased (Arriaza, \u003cspan class=\"CitationRef\"\u003e1995\u003c/span\u003e; Guillen, \u003cspan class=\"CitationRef\"\u003e1997\u003c/span\u003e; Sep\u0026uacute;lveda et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e; Standen, \u003cspan class=\"CitationRef\"\u003e1997\u003c/span\u003e). For example, the well-documented preparation of the so called, black and red mummies (Arriaza \u0026amp; Standen, \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Arriaza et al., \u003cspan class=\"CitationRef\"\u003e2023a\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003eb\u003c/span\u003e; Sep\u0026uacute;lveda et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e). Arriaza et al., \u003cspan class=\"CitationRef\"\u003e2023b\u003c/span\u003e recently proposed that due to heavy highland rains and steep slopes where the mantles are found, Mn rocks break down easily and in turn, reach the lowlands and form part of the river terraces. Along these lowland terraces, Chinchorro people could have extracted the Mn for use in the mortuary context described (Arriaza \u0026amp; Standen, \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Arriaza et al., \u003cspan class=\"CitationRef\"\u003e2023a\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003eb\u003c/span\u003e; Ossa, \u003cspan class=\"CitationRef\"\u003e1970\u003c/span\u003e; Sep\u0026uacute;lveda et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e; Van Hoesen et al., \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). This Mn integration in the Lluta River ecosystem highlights not only the geological and landscape dynamics but also a profound cultural significance of the natural resources, linking the Lluta River to the Chinchorro's artistic and mortuary expressions.\u003c/p\u003e\n\u003cp\u003eThis work describes Mn levels present in the current sediments of the Lluta River to test the solubilization processes. Sediments from the Lluta riverbed at various elevations were sampled for the quantification of Mn, considering water-soluble, exchangeable forms, and acid-soluble forms in the sediment. We focused on the possible Mn sources available to the ancient archaic populations of northern Chile and its potential effects upon modern populations.\u003c/p\u003e\n\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e\n\u003ch2\u003e1.1 Local water processes and Mn mobility\u003c/h2\u003e\n\u003cp\u003eThe heavy rains in the Andean Chilean highlands (January-February) contribute to physical and chemical weathering of the soil and native minerals. The natural weather phenomena occurring in the highlands and in the Lluta River basin are visible during the rainy season, where for example during February 2019, the river changed from an annual average flow of 3.01 m\u003csup\u003e3\u003c/sup\u003e/s to 19.53 m\u003csup\u003e3\u003c/sup\u003e/s (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://snia.mop.gob.cl/BNAConsultas/reportes\u003c/span\u003e\u003c/span\u003e). The colluvial and alluvial processes along the river facilitate the transportation of weathered material such as rocks, small stones, gravel, and fine sediments to lower elevations along the Lluta River. These materials undergo physical and chemical weathering according to seasonal water fluctuations, which results in a reduction of particle size for Mn-rich materials that are eventually deposited along the river. The resulting smaller particles possess a larger surface area, which facilitates chemical reactions within the aqueous solution of the Lluta River, transforming the Mn oxide into free Mn\u003csup\u003e2+\u003c/sup\u003e cations. Increased acidity in the Lluta River is produced by the Azufre River contribution, one of the tributaries at the Lluta River headwaters (ca. 3,982 meters above sea level or masl). This facilitates ionic speciation and interactions with the sediments depending on the pH of the water (Zumaeta, \u003cspan class=\"CitationRef\"\u003e1981\u003c/span\u003e).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n\u003ch2\u003e1.2 The produced ionic Mn\u003c/h2\u003e\n\u003cp\u003eThe Mn cation is an ionic chemical species, which becomes part of the solutes dissolved in the water of the river and can also be reactive with undissolved sediment. The Lluta River sediment is made up of sand, silt, clay, and various oxides-hydroxides that are deposited on the bank and riverbed after flooding. The Mn cation can interact with clay minerals through ion exchange reactions and can be transported by the river in times of flooding. These processes led to the formation of various ionic forms of Mn in the dry river deposits located on the banks of the Lluta River after the rainy seasons.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003e1.3 The different quantifiable forms of Mn\u003c/h2\u003e\n\u003cp\u003eTo quantify the Mn present in the sediments we used three approaches:\u003c/p\u003e\n\u003col style=\"list-style-type: lower-alpha;\"\u003e\n\u003cli\u003e\n\u003cp\u003eWater-soluble form: concentration of Mn in the sediment released by the action of water through the phenomenon of solubilization and hydrolysis.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eExchangeable form: the Mn in the sediment retained by physical adsorption in the cation exchange complex and released by reaction with the aqueous solution of the potassium cation.\u003c/p\u003e\n\u003c/li\u003e\n\u003cli\u003e\n\u003cp\u003eAcid soluble form: the Mn in the sediment typical of oxide and oxide-hydroxide type minerals of the element.\u003c/p\u003e\n\u003c/li\u003e\n\u003c/ol\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003ch2\u003e1.4 Conductivity and pH\u003c/h2\u003e\n\u003cp\u003eIn the study of sedimentary processes, the behavior of mineral components plays a crucial role the chemical and physical weathering of minerals resulting in the water-soluble fraction of Mn in the sediment, comprising inorganic and ionic salts. This fraction, when interacting with water, dissolves various saline species, thereby imparting electrolytic properties to the solution, as evidenced by electrical conductivity measurements.\u003c/p\u003e\n\u003cp\u003eThese interactions can also trigger hydrolysis reactions, altering the pH of the aqueous system. An acidic pH increases the likelihood of dissolving oxide-type components, including Mn oxides, contributing further to the water-soluble form of Mn. This study considers the sediment fractions, differentiated by particle size and by the weighted concentration of the total Mn transported in the fractions, at known location along the river.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n\u003ch2\u003e1.5 Overall considerations\u003c/h2\u003e\n\u003cp\u003eThe quantification of Mn concentrated in river sediments has archaeological implications. Its quantification allow us to determine whether the riverbed sediments have enough Mn in oxide form that could have been used by the Chinchorro populations to decorate their dead. It also provides new data to debate the potential toxicity that these sediments could have had on the health of the population that used this material. This is highly relevant considering overexposure to high Mn concentrations has toxic effects on humans (Arriaza \u0026amp; Galaz-Mandakovic, \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e; ATSDR, 2012; Guerra et al., \u003cspan class=\"CitationRef\"\u003e2016\u003c/span\u003e; Lucchini et al., \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Mena et al., \u003cspan class=\"CitationRef\"\u003e1967\u003c/span\u003e; O\u0026rsquo;Neal \u0026amp; Zheng, \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e; Ram\u0026iacute;rez y Ayala, \u0026amp; Azcona-Cruz (2017). The study of Mn in river sediment has current health importance (e.g., environmental contamination).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n\u003ch2\u003e2.1 Collection of sediment samples\u003c/h2\u003e\n\u003cp\u003eDry sediment samples were collected from six different areas along the Lluta River after eight (8) months of the highland season rainfall. Before sampling the area, the characteristics of the riverbed were visually examined, looking for dry sediment banks visible to the naked eye. The sediment sought was characterized by the presence of clays and well-defined deposits. About 2 kg of soil per sample was collected at each area, using a plastic shovel cleaned with distilled water before collecting the next sample. Soil samples were collected in polyethylene bags. Each sample was assigned an identification code based on its extraction area, dated, and labeled including its GPS location and altitude, using a Garmin GPSMAP 62s Series (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e and Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). Samples were transported to the Universidad de Tarapac\u0026aacute; Chemical Laboratory for analysis. The sediment sample gathering was undertaken from higher to lower altitudes. Consequently, in the text, the terms 'area', 'zone', and 'sediment number' refer to the same sample and are used interchangeably.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eLocation of the sample collected along the Lluta riverbed.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eSediment sample\u003c/p\u003e\n\u003cp\u003e(Zone)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003emasl\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eUTM, grid zone 19K\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eX (East)\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eY (North)\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003c/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1,328\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e412495\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7973598\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e1,124\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e406480\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7969826\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e3\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e872\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e397732\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7966086\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e527\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e386800\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7959487\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e23\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e361963\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7964444\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e6\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e360255\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"char\" char=\".\"\u003e\n\u003cp\u003e7963591\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/tbody\u003e\n\u003c/table\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n\u003ch2\u003e2.2 Treatment of the soil samples\u003c/h2\u003e\n\u003cp\u003e\u003cem\u003eSieving of the soil samples\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eEach sediment sample was manually pulverized using a porcelain mortar, avoiding generation of high pressure to causes crystalline breakage. The resulting material was then fractionated using a stainless steel sieve model Retsch AS 200 digit CA, with five different mesh aperture sizes, \u0026le;\u0026thinsp;1,000 \u0026micro;m (coarse sand); \u0026le;500 \u0026micro;m (medium sand); \u0026le;250 \u0026micro;m (fine sand); \u0026le;90 \u0026micro;m (very fine sand); and \u0026le;\u0026thinsp;63 \u0026micro;m (very fine sand, silt and clay). Following sediment separation, each fraction was packed into a plastic bag and labeled for subsequent analysis.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eChemical treatment and analysis of the sediment fractions\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003ea) Water-soluble form (Mn, conductivity, and pH): 50 mL of distilled water (Electrical Conductivity - EC\u0026thinsp;\u0026le;\u0026thinsp;3 \u0026micro;S/cm) was added to 20.00 g mass of the corresponding sediment fraction to get a 2.5 weight/volume ratio. The solution was placed in a 100 mL wide-mouth polypropylene bottle with a screw cap and properly labeled. The container was hermetically sealed and shaken orbitally for two hours at 250 rpm.\u003c/p\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eAfter hydrolysis reactions between the reactive phases in the solubilization reached equilibrium, the flask was shaken manually to homogenize the aqueous mixture. Then electrical conductivity and pH were measured in the suspension of the sediment in water for each of the samples, using a conductivity meter calibrated with 0.01M KCl solution and a pH meter previously calibrated at pH 4 and 7.\u003c/p\u003e\n\u003cp\u003eAfter the pH measurements were completed, the aqueous mixture of the sediment was filtered through Whatman 2 qualitative paper and packed in a hermetically sealed polypropylene bottle. The Mn concentration was quantified using this aqueous solution.\u003c/p\u003e\n\u003cp\u003eb) Exchangeable form: The treatment of the sediment to quantify its exchangeable form was carried out in a similar way to the treatment of the water-soluble form, except that the reagent solution with the sediment was KCl of 1M concentration adjusted to pH 7.0. The Mn concentration was quantified in the respective filtrate of the potassium solution.\u003c/p\u003e\n\u003cp\u003ec) Acid soluble form: A mass of 0.5\u0026thinsp;\u0026plusmn;\u0026thinsp;1*10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e g of the sediment sample and its respective fractions were weighed and placed in a beaker. 10 mL of 6M hydrochloric acid (HCl) A.C.S. was added to the beaker. The mixture was heated under a fume hood in a semi-closed system with constant stirring on a hot plate, bringing it to a boil until the volume was reduced by half.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\n\u003cp\u003eAfter room temperature cooling (20\u0026ndash;25 \u003csup\u003eo\u003c/sup\u003e C), 25 mL of distilled water was added to ensure solubility, while monitoring the temperature. Once complete solubilization of the ionic forms was achieved at room temperature, the mixture was quantitatively transferred to a 100 mL volumetric flask and made up to volume with distilled water. The decanted solid phase mixture was filtered through qualitative Whatman 2 paper, and the filtrate was placed in a polypropylene container with a tight-fitting lid.\u003c/p\u003e\n\u003cp\u003eThe total concentration of Mn was quantified using this acid solution. The respective Mn concentrations of the water-soluble and exchangeable forms were subtracted from this concentration to obtain the Mn concentration corresponding to the acid-soluble form.\u003c/p\u003e\n\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n\u003ch2\u003e2.3 Quantification of manganese\u003c/h2\u003e\n\u003cp\u003eThe Mn analyte contained in each of the solutions obtained from the different extraction methods was quantified using Atomic Absorption Spectroscopy, Agilent Technologies FSAA 240, with the following operating parameters: Hollow Cathode Lamp: Mn; PROMT (Precision Optimized Measurement Time) measurement system; Flame Type: Air- Acetylene (oxidant); Measurement replicates: 3 for calibration standard and sample; Read delay time: 2 seconds; Measurement time: 2 seconds; Wavelength: 279.5 nm; Slit width: 0.2 nm; Background correction: On (Deuterium-D\u003csub\u003e2\u003c/sub\u003e lamp); Calibration range in the aqueous matrix, KCl matrix and HCl matrix: 1 to 6 mg/L; Calibration algorithm: New rational, providing a rational best-fit line in the absorbance versus concentration domain; Calibration curve: Concentration = (a *Absorbance2) + (b * Absorbance)\u0026thinsp;+\u0026thinsp;c; Characteristic concentration: 0.045 mg/L; Correlation coefficient (r): 1; Limit of Detection (LOD), sd*3, for linear zero-intercept curve: 0.014 mg/L.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n\u003ch2\u003e2.4 Statistical analyses\u003c/h2\u003e\n\u003cp\u003eThe data was analyzed using Excel, SPSSV25, and Statgraphics V18. Graphs and a Spearman correlation were undertaken (non-parametric samples). A Shapiro-Wilk normality, Krukall-Wallis, and Games-Howell post Hoc analyses for non-parametric data were undertaken.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Particle size of the sediment\u003c/h2\u003e\n \u003cp\u003eThe results in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e show that all five size fractions are present in each of the sediments analyzed. There is a tendency for the highest percentages of mass distribution to be found in the smallest size fraction of the sediment. The particle size in the collected sediment may be variable to some degree depending on the Mn forms. For example, the exchangeable Mn is assumed to interact with the clay fraction which facilitates the adsorption of the Mn\u003csup\u003e2+\u003c/sup\u003e cation through the simple attraction of charges, resulting in non-specific and exchangeable physical adsorption.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePercentage distribution of the mass of each sediment fraction according to the sampling zones.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSediment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"6\" align=\"left\"\u003e\n \u003cp\u003ePercent of fraction in the sediment according to zone sampled\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAverage\u003c/p\u003e\n \u003cp\u003e(Fraction)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eSediment category\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFraction \u0026micro;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;1000\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.85\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCoarse sand\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;500\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMedium sand\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;250\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e35.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFine sand\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.50\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVery fine sand\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;63\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e45.40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e35.00\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e46.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e75.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e36.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e44.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVery fine sand, silt and clay\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e99.9\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e100\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e100.1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e100\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e99.9\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e99.9\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e100\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e-\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e displays the average percentage distribution of each fraction across six sediment samples. In the \u0026le;\u0026thinsp;63 \u0026micro;m fraction, consisting of very fine sand, silt, and clay, we found that the highest average percentage of total Mn material is 44.68%. This increased to 56.40% when considering the \u0026le;\u0026thinsp;90 \u0026micro;m fraction of very fine sand and reached up to 77.43% with the inclusion of the \u0026le;\u0026thinsp;250 \u0026micro;m fraction corresponding to fine sand. In general, the data showed a physical weathering of the larger particles entering the riverbed resulting in smaller particles at the lowlands (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, Zones 5 y 6).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 Electric conductivity\u003c/h2\u003e\n \u003cp\u003eThe electrical conductivity values in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e reveal the significantly elevated presence of ionic activity in the aqueous solution of the overall sediment pool, including water-solubilized Mn.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eElectrical conductivity of the water-solubilized sediment solution.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSediment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"6\" align=\"left\"\u003e\n \u003cp\u003eEC \u0026micro;S/cm in sediment-water according to the zone sampled\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAverage Fraction EC\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFraction / \u0026micro;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;1000\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2,790\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5,280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6,750\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e786\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5,520\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7,460\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4,764.33\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;500\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1,849\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4,950\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8,240\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e720\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5,160\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4,900\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4,303.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;250\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e853\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4,790\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10,200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1,217\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4,090\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7,380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4,755.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e866\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4,200\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10,550\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1,694\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2,170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6,990\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4,411.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;63\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1,187\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4,050\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9,600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1,618\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2,070\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5,760\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4,047.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1,509\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e4,654\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e9,068\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1,207\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e3,802\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e6.498\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e4,456.33\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS. D.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e822.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e516.94\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1,566.80\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e452.93\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1,623.41\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e1,122.91\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e1,017.53\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 pH\u003c/h2\u003e\n \u003cp\u003epH data from sediments collected at different zones of the Lluta River (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e) showed a gradient from low acidity to slight alkalinity (pH 6.1\u0026ndash;7.9), with a general decrease in pH in finer fractions (\u0026le;\u0026thinsp;90 \u0026micro;m and \u0026le;\u0026thinsp;63 \u0026micro;m), particularly in lower elevation zones 5 and 6.\u003c/p\u003e\n \u003cp\u003eThis pattern indicated a higher acidification influence in fine particles. The coarser fractions exhibited a higher pH, potentially reflecting their chemical stability and lower reactivity. These pH variations by particle size and zone may suggest differences in the source and nature of the sedimentary material, with potential implications for the mobility of Mn cations.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003epH values in sediment water.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eSediment\u003c/p\u003e\n \u003cp\u003eFraction / \u0026micro;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"6\" align=\"left\"\u003e\n \u003cp\u003epH in sediment water according to zone sampled\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAverage fraction pH\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;1000\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;500\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.32\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;250\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;63\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.7\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.4\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e6.6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.23\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS.D.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.16\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.15\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.13\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.14\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.26\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.37\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cem\u003ea) Water-soluble form\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eThe results shown in Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e correspond to the concentration of Mn in its water-soluble form, i.e. the Mn element is present in all the fractions (Average sediment 0.18\u0026ndash;48.68 \u0026micro;g/g).\u003c/p\u003e\n \u003cp\u003eAlthough the Mn element is present in all the fractions, in Zone 1 (1,328 masl) its concentration is practically extremely low or undetectable in each of the fractions. In contrast, the maximum concentrations of Mn revealed among all fractions tend to be present in Zone 6 with of maximum of 74.5 \u0026micro;g/g in the \u0026le;\u0026thinsp;90 \u0026micro;m fraction.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eWater soluble Mn concentration.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eSediment\u003c/p\u003e\n \u003cp\u003eFraction \u0026micro;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"6\" align=\"left\"\u003e\n \u003cp\u003eMn \u0026micro;g/g sediment according to zone sampled\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAverage Mn fraction\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;1000\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e51.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e34.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;500\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e60.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e46.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;250\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e62.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.27\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e74.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.45\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;63\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e24.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.92\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.9\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e34.8\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e60.1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e11.8\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e15.9\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e243.4\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e61.15\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.18\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e6.96\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e12.02\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e2.36\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e30.78\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e48.68\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e16.83\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS.D.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.35\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.32\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e3.37\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.37\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e24.40\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e20.14\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e4.58\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThis tendency of greater concentration of Mn in the lowlands aligned with the fluvial transport dynamics and suggested an increased potential for Mn bioaccumulation in the sediment matrix towards the river\u0026apos;s mouth. Thus, at some point in the river, the larger clasts are broken down to a fine fraction that is carried to the mouth of the river. This finding is also significant for environmental impact studies and water resource management considering that large agriculture fields are present in the lowlands.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eb) Exchangeable form\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e shows the clay particles have more Mn in lower elevation areas (Zones 5 and 6) and Mn particles were effectively transported as non-dissolved solids in the river water flow. The desorption or cation exchange phenomenon occurred about the availability of Mn in the aqueous matrix and its cationic form Mn\u003csup\u003e2+\u003c/sup\u003e which can be subsequently assimilated by plant organisms.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab6\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eExchangeable Mn concentration.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSediment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"6\" align=\"left\"\u003e\n \u003cp\u003eMn \u0026micro;g/g sediment according to zone sampled\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAverage Mn\u003c/p\u003e\n \u003cp\u003efraction\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFraction \u0026micro;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;1000\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e46.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;500\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e20.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e76.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;250\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e57.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.23\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e52.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.47\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;63\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.24\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.39\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e26.7\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e22.6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e31.7\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e96.0\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e247.5\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e70.98\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.28\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e3.54\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e4.52\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e6.34\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e19.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e49.50\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e13.90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS.D.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e0.13\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e3.34\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e2.13\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e1.65\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e16.04\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e19.89\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e7.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThe concentration of exchangeable Mn varies according to the zone in sediments. For all the Zones, the highest concentration of Mn was found in Zone 6 with 76.7 \u0026micro;g/g. This finding is comparable to that of Mn in its soluble form.\u003c/p\u003e\n \u003cp\u003e\u003cem\u003ec) Acid soluble form\u003c/em\u003e\u003c/p\u003e\n \u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e indicates that there is significant spatial variability in the concentration of acid-soluble Mn within the sediments from different zones along the Lluta River. Zones 5 and 6 showed the highest total concentrations suggested either a localized source of Mn or less effective dilution and transport by the river system in these areas. Notably, the smallest particle size (\u0026le;\u0026thinsp;63 \u0026micro;m) in Zone 3 contains the highest single concentration of Mn, which is consistent with the understanding that finer particles can have higher metal concentrations due to their larger surface area to volume ratio.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab7\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eAcid soluble Mn concentration.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSediment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"6\" align=\"left\"\u003e\n \u003cp\u003eMn \u0026micro;g/g sediment according to zone sampled\u003c/p\u003e\n \u003c/th\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eAverage Mn fraction\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFraction \u0026micro;m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;1000\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e309\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e434\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e315\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e352\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e917\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e973\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e550.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;500\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e871\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e408\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e609\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e394\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e964\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e708.33\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;250\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e729\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e581\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e708\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e587\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e826\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e944\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e729.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;90\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e617\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e640\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e854\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e645\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e670\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e847\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e712.17\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026le;\u0026thinsp;63\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e642\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e623\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.114\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e597\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e641\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e839\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e742.67\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e3,168\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e2,686\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e3,600\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e2,575\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e4,018\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e4,607\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e3,442.33\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e633.60\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e537.20\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e720.00\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e515.00\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e803.60\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e921.40\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e688.47\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS.D.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e206.86\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e108.62\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e295.67\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e132.30\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e144.38\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003e74.70\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e\u003cstrong\u003e160.42\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eThis form of Mn in the sediment represents the phenomenon of physical weathering due to water flow. There is a reduction of the original size of the Mn rock along the riverbed.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Correlation comparisons\u003c/h2\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e shows a matrix correlation between the three Mn extraction methods used and their relationship with electrical conductivity, pH, elevation, and particle size. The Spearman correlation coefficient indicates the strength and direction of the associations.\u003c/p\u003e\n \u003cp\u003eThe three Mn extraction methods demonstrate a positive correlation with each other, the strongest being between water-soluble Mn and exchangeable Mn (r\u0026thinsp;=\u0026thinsp;0.72). This suggests that despite differences in extraction techniques, there is a significant relationship in Mn levels detected by these methods and that extraction techniques do not affect the results.\u003c/p\u003e\n \u003cp\u003eA marked negative correlation (r =-0.91) is observed between elevation and the concentration of available exchangeable Mn, indicating higher availability of exchangeable Mn at lower elevations, especially in coastal areas. Instead, electrical conductivity, shows a low to moderate correlation with Mn extraction methods, indicating that it is not a reliable indicator for predicting the concentration of soluble Mn ions.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Comparison between Mn extraction methods\u003c/h2\u003e\n \u003cp\u003eThe water-soluble, exchangeable forms and acid soluble showed a certain tendency for the concentration of Mn in its oxidized species to be higher in the areas closest to the river mouth (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). In some way, this could be validated by a particle size of Mn oxides small enough in their solid aggregate state to be transported by the fluvial system to a lower elevation and finally deposited with other solid materials of the system\u0026apos;s matrix.\u003c/p\u003e\n \u003cp\u003eIn addition, the different methods are at a markedly higher ratio, in the order of 19 to 3,090 and 12 to 2,060 times respectively relative to the average values at their statistical maximum and minimum. Comparing the three extraction methods, the acid-soluble Mn form removed a higher concentration of manganese from the sediments. Taking into consideration the weathering processes already described, we can conclude that in all methods the lowlands samples have the highest concentration of Mn.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 Statistical considerations\u003c/h2\u003e\n \u003cp\u003eThe Shapiro-Wilk normality test indicated that both soluble Mn and exchangeable Mn present a non-parametric distribution (p-value\u0026thinsp;=\u0026thinsp;0.001), while acid-soluble Mn present a parametric distribution (p-value\u0026thinsp;=\u0026thinsp;0.332). Considering that two variables (soluble Mn and exchangeable Mn) presented a non-parametric distribution, a Kruskall-Wallis analysis was used, which resulted in a test value of 59.50 and a p-value of 0.001. This statistical test verifies that there are significant differences between the different Mn extraction methods. Thus, the Games-Howell post hoc test for non-parametric data shows a distribution cluster grouping the extraction of soluble Mn and exchangeable Mn as one group (p-value\u0026thinsp;=\u0026thinsp;0.845) and the acid-soluble Mn into another group (p-value\u0026thinsp;=\u0026thinsp;0.001).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 Archaeological implications\u003c/h2\u003e\n \u003cp\u003eIn the past, during different periods, ancient people probably could have accessed Mn highland sources to use in their rock art expressions (Sep\u0026uacute;lveda et al., \u003cspan class=\"CitationRef\"\u003e2013\u003c/span\u003e) or for the ornamentation of the Chinchorro mummies. Nevertheless, for the Chinchorro it has been recently argued that the Chinchorro populations extracted Mn from the lowlands of Arica (Arriaza et al., \u003cspan class=\"CitationRef\"\u003e2023b\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eAccording to the various types of chemical analyses, the higher levels of Mn concentration found in the sediments of the Lluta riverbed indicate that coastal populations living near Arica river mouths (e.g. Lluta River) would potentially have a higher level of exposure than populations inhabiting higher elevation floors at different stages of cultural development in the region. Although these Mn concentration levels, in relative terms, are low from the perspective of the raw material available (Mn pigment) not reaching a significant percentage. The overall average of the sediment fractions and zone concentration was less than 0.1%. However, this low concentration could hypothetically have been added to or accumulated in the mineralogical matrix of the Mn pigments used by the ancient Chinchorro populations. The mineral matrix used in the form of paste to ornament the Chinchorro mummies required water for its preparation, a vital element that must have been extracted from the water resources near the coast.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\n \u003ch2\u003e3.8 Human health implications\u003c/h2\u003e\n \u003cp\u003eOn the other hand, the Chilean standard NCh 409, recommends that the level of Mn in drinking water should not exceed 0.1 mg/L (0.1 ppm), and the NCh 1333 applicable to water for irrigation suggested 0.2 mg/L (0.2 ppm). Nevertheless, the accumulation of Mn in the river sediments and the waters could have created a potential risk for the ancient settlers as well as for the modern ones.\u003c/p\u003e\n \u003cp\u003eOverexposure to Mn either by ingestion of water or by suspended particulate matter is harmful to health (Dey et al., 2023; Lucchini et al., 2015; O\u0026rsquo;Neal \u0026amp; Zheng, 2015; Riojas-Rodr\u0026iacute;guez et al., 2010; Sol\u0026iacute;s-Vivanco et al., 2009; Ram\u0026iacute;rez y Ayala, \u0026amp; Azcona-Cruz, 2017; Tchernitchin et al., 2015; Wu et al., 2022). The latter source of input is more harmful considering the alternative of a probable acute or short-term poisoning phenomenon by inhaling the Mn duct, which mainly affects miners (Mena et al., 1967). Although today the current populations of Arica do not practice Mn mining, agricultural products in the Lluta Valley could hypothetically bioaccumulate Mn from the use of Mn-contaminated irrigation water. Elsewhere scholars have reported Mn in crops (Awino et al., 2021). Average Mn in soil has been reported as 330 mg/kg with a range of 40 to 900 mg/kg (Lucchini et al., 2015). Table 5 on water-soluble Mn shows that river sediments in the geographical zones 3, 5 and 6 have Mn levels higher than the lower range reported in the literature with 60.1; 153.9 and 243.4 \u0026micro;g/g Mn.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe eventual natural disposition of Mn oxide rocks in the Lluta riverbed, coming from the mineral mantle, can be weathered by both chemical and physical mechanisms. The transport of materials generated by the flow of the river and the sedimentation of these, together with the evaporation of water on the riverbanks, generated solid sediments that present chemical and physical properties revealing the phenomenon of weathering.\u003c/p\u003e\n\u003cp\u003eThe presence of both water-soluble and exchangeable forms of Mn revealed a chemical weathering process associated with the Mn oxide ore, and the presence of the acid-soluble form of Mn suggests a physical weathering process of the Mn oxide ore.\u003c/p\u003e\n\u003cp\u003eThe higher Mn concentration associated with the size-reduced Mn oxide material compared to the concentration of both water-soluble and exchangeable Mn or the addition of the latter two revealed that physical weathering of the original Mn oxide material is the main process of size reduction of the Mn oxide material.\u003c/p\u003e\n\u003cp\u003eThere is increasing fine-grained Mn in lower elevations of the riverbed. However, the total Mn transported and the low concentration of Mn oxide ore, denoted that Lluta riverbed are not a significant source of Mn to be used for mortuary preparation. Certainly, the presence of Mn in the riverbed would be varied according to the magnitude of the alluvial phenomena, the ENSO fluctuations, and the amount of rain affecting the Mn mantles in the highlands. However, the riverbed does not provide enough Mn compared to the river terraces to aid in the preparation of the Chinchorro mummies.\u003c/p\u003e\n\u003cp\u003eMn in the riverbed sediments and dissolved in its waters could have been eventually ingested by ancient people, whose concentration and effects need to be studied. On the other hand, the waters of the Lluta River are currently used for agriculture so they should be monitored to verify that the availability and absorption of Mn does not present a risk to the current population due to bioaccumulation in the agricultural products irrigated with these waters.\u003c/p\u003e"},{"header":"Declarations","content":" \u003ch2\u003eConflict of interest\u003c/h2\u003e \u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e \u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eSpecific Contributions of the AuthorsL.F.: Conceptualization, Methodology, Investigation, Supervision, Resources, Writing \u0026ndash; review \u0026amp; editing.B.A.: Conceptualization, Methodology, Investigation, Supervision, Resources, Funding acquisition, Project administration, Writing \u0026ndash; review \u0026amp; editing.A.V.: Methodology, Formal analysis, Writing \u0026ndash; review \u0026amp; editing.C.C.: Methodology, Laboratory analysis, Writing \u0026ndash; review \u0026amp; editing.S.B.: Methodology, Laboratory analysis.J.V.H.: Conceptualization, Writing \u0026ndash; review \u0026amp; editing.All authors participated in the manuscript review process.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eWe thank Fondecyt 1210036 grant for financial support.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAgency for Toxic Substances and Disease Registry (ATSDR), (2012). \u003cem\u003eToxicological Profile for Manganese\u003c/em\u003e. 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Polimetales en agua de Arica-Parinacota: Posibles or\u0026iacute;genes y efectos en la salud. \u003cem\u003eCongreso Geol\u0026oacute;gico Chileno XIV\u003c/em\u003e. La Serena, pp. 296-299.\u003c/li\u003e\n\u003cli\u003eVan Hoesen, J., Arriaza, B., Ryan, P., \u0026amp; Grady, C. (2018). A multianalytical approach for identifying a manganese source for the black pigment of the Chinchorro mortuary palette. \u003cem\u003eGeoarchaeology,\u003c/em\u003e 34, 322-335.\u003c/li\u003e\n\u003cli\u003eWu, R., Yao, F., Li, X., Shi, C., Zang, X., Shu, X., Liu, H., \u0026amp; Zhang, W. (2022). Manganese Pollution and Its Remediation: A Review of Biological Removal and Promising Combination Strategies. \u003cem\u003eMicroorganisms\u003c/em\u003e, 10, 2411.\u003c/li\u003e\n\u003cli\u003eZumaeta, D. (1981). Constituyentes qu\u0026iacute;micos en varias aguas de riego de las provincias de Arica y Parinacota, Primera Regi\u0026oacute;n - Chile. Revista Arica, Serie Qu\u0026iacute;mica, Universidad del Norte, 1327-169.\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":"Manganese traces, Chinchorro, Riverbanks, Mineral, Arica y Parinacota","lastPublishedDoi":"10.21203/rs.3.rs-4253081/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4253081/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe ancient coastal populations of northern Chile called Chinchorro used manganese (Mn) oxide extensively for the preparation and ornamentation of their deceased. The possible sources of extraction of this mineral have been debated in several studies. This work focuses on the study of dry sediments from the Lluta riverbed in the Arica y Parinacota region to characterize Mn concentrations in alluvially transported material at different points along the river. Six riverbed sediment samples were collected from an altitude of 1,328 masl to 6 masl. The samples were sieved into five-size fractions and Mn concentrations were measured using atomic absorption spectroscopy. It was found that Mn concentrations vary inversely proportional to altitude with a correlation coefficient of -0.91. The highest Mn levels are found in samples near the coast with the following values: total water-soluble Mn 243 \u0026micro;g/g, total exchangeable Mn 248 \u0026micro;g/g, and total acid-soluble Mn 4,607 \u0026micro;g/g. These levels of Mn would not correspond to a primary or important source for the extraction of black Mn ore by the archaic inhabitants for mortuary preparation of the Chinchorro mummies. Nevertheless, the presence of Mn in the riverbed raises questions about the health consequences for the ancient populations and the importance of monitoring Mn in the water due to possible bioaccumulation of this mineral in agricultural products of the area.\u003c/p\u003e","manuscriptTitle":"Study of manganese traces in fluvial sediments along the Lluta riverbanks in the Arica and Parinacota region, northern Chile: Archaeological and current implications","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-18 00:01:02","doi":"10.21203/rs.3.rs-4253081/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":"d4c2f528-6861-49cf-b830-9c1261a97ab0","owner":[],"postedDate":"April 18th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-22T08:47:36+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-18 00:01:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4253081","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4253081","identity":"rs-4253081","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}