Soil Arsenic Concentrations Research Articles

Polycyclic Aromatic Hydrocarbons, Mercury and Arsenic Content in Soils of Larsemann Hills, Pravda Coast and Fulmar Island, Eastern Antarctica.

This study is aimed at investigation of various potential contaminants (arsenic, mercury and polycyclic aromatic hydrocarbons) content in soils of different landscapes of Eastern Antarctica ice-free areas. Our data not only showed that intensive human impact might result in significant direct contamination of surrounding landforms, but also revealed a specific role of ornithogenic transport in distribution of contaminants. Analysis revealed that the contents of investigated elements were 0.100-8.055mgkg-1 (arsenic), 0.025-0.027mgkg-1 (mercury) in Larsemann Hills and 0.100-1.213mgkg-1 (arsenic), 0.023-0.593mgkg-1 (mercury) in vicinities of Mirny station and Fulmar Island. Accumulation of some elements in guano-derived and moss materials lead to higher values of other soil pollution indices at natural sites. Results of our study revealed the predominance of light molecular weight PAHs (fluorene and acenaphthylene) in studied soils. Results of our study are not completely in agreement with the idea of an practically uncontaminated Antarctic ecosystem which was previously reported for Eastern Antarctica ice-free areas. Various human activities carried out at local scale have been found to be responsible for increase of metal levels in studied Antarctic environments.

Elemental analysis in surface soil and dust of roadside academic institutions in Dhaka city, Bangladesh and their impact on human health

The increasing industrial activities, number of vehicles on road and population in large cities causes the contamination of air in urban environment, and eventually affect human health. Therefore, the aim of this study was to collect soil and dust samples from twelve roadside academic institutions in Dhaka City, Bangladesh. One of the twelve sites is control site for this study. The elemental (Ca, Fe, K, Ti, Sr, Zn, Zr, Rb, Cr, Ni, Pb and Cu) concentration in soil and dust samples were analyzed by XRF technique. The metals concentration in dust and soil samples followed the following order: Fe > Ti > Sr > Zn > Zr > Rb > Pb > Cu, and Fe > Ti > Zr > Sr > Rb > Zn > Cu > Pb > As, respectively. As expected, the most elemental concentration at the control site, which was situated inside a village and ~ 1 km far away from the road, was lower compared with those in soil and dust samples. Average As concentration (16.52 mg/kg) in soil was observed to be three times higher than its background value. The concentration of Pb in the dust sample of a school at Sadarghat (136.04 mg/kg) was significantly higher than the other sites. We observed that the mean concentration for most of the metals had a higher concentration than the background values set by Chinese Environmental Protection Administration (CEPA), except for K and Zr. Soil samples were analyzed to determine the percentage of organic matter by dry combustion technique, and the average amount of organic matter in soil samples was 1.42%. Conversely, the contamination levels of heavy metals were assessed based on the geo-accumulation index ( I geo ), enrichment factor ( EF ) and contamination factor (CF). Subsequently non-carcinogenic health risk was determined using lifetime average daily dose ( LADD ). The non-carcinogenic health risk was found to be more prominent for children than that for adults. No significant carcinogenic health risk was found in the study area. • Concentration of Ca, Fe, K, Ti, Sr, Zn, As, Zr, Rb, Cr, Ni, Pb and Cu in soil and dust were determined by XRF • Average concentration for most of the metals have higher concentration than the background value. • Average arsenic concentration in soil was observed to be three times higher than its background value • Non-carcinogenic health risk was found to be more prominent for children than that for adults. • No significant carcinogenic health risk was found in the study area.

Análisis de cadmio, plomo, níquel y arsénico en plantas de cacao y derivados: Industria Alimentaria

INTRODUCCIÓN. El cacao es una materia prima producida principalmente en varios países de América, África y Asia. El cultivo de cacao es una de las principales actividades socio-económicas, en el Ecuador, siendo el primer exportador de cacao fino de aroma en grano de América. OBJETIVO. El presente artículo tiene como objetivo la revisión de investigaciones que analicen la problemática del contenido de cadmio, plomo, arsénico y níquel en los suelos de plantaciones y en productos derivados del cacao. MÉTODO. Se realizó una revisión sistemática consultando 18 artículos de las principales bases de datos. RESULTADOS. Se encontraron análisis de metales pesados relacionados con el cacao en distintos países del mundo. DISCUSIÓN Y CONCLUSIONES. Se ha encontrado que el cultivo de cacao y sus derivados postcosecha pueden tener concentraciones elevadas de cadmio, plomo, níquel y arsénico, la legislación no es lo suficientemente clara y en ciertos casos no se han desarrollado límites para ciertos metales pesados Trabajar en modelos predictivos para determinar una posible contaminación de metales pesados resulta indispensable para el sector industrial, así como las herramientas de mitigación en campo y producción.

Pteris vittata Arsenic Accumulation Only Partially Explains Soil Arsenic Depletion during Field-Scale Phytoextraction

Soil arsenic heterogeneity complicates our understanding of phytoextraction rates during arsenic phytoextraction with Pteris vittata, including in response to rate stimulation with nutrient treatments. In a 58-week arsenic phytoextraction field study, we determined the effects of soil arsenic concentrations, fertilizer application, and mycorrhizal fungi inoculation on P. vittata arsenic uptake rates, soil arsenic depletion, and arsenic soil–plant mass balances. Initial soil arsenic concentrations were positively correlated with arsenic uptake rates. Soil inoculation with mycorrhizal fungus Funneliformis mosseae led to 1.5–2 times higher fern aboveground biomass. Across all treatments, ferns accumulated a mean of 3.6% of the initial soil arsenic, and mean soil arsenic concentrations decreased by up to 44%. At depths of 0–10 cm, arsenic accumulation in P. vittata matched soil arsenic depletion. However, at depths of 0–20 cm, fern arsenic accumulation could not account for 61.5% of the soil arsenic depletion, suggesting that the missing arsenic could have been lost to leaching. A higher fraction of arsenic (III) (12.8–71.5%) in the rhizosphere compared to bulk soils suggests that the rhizosphere is a distinct geochemical environment featuring processes that could solubilize arsenic. To our knowledge, this is the first mass balance relating arsenic accumulation in P. vittata to significant decreases in soil arsenic concentrations under field conditions.

Exposure risk assessment, pollution level, and source identification of arsenic in soil: A case study of the Bardsir Plain (southeastern Iran)

ABSTRACT In this study, we investigated the total arsenic concentration in the soil and the related human exposure risks in the central part of the Bardsir Plain in southeastern Iran. The results show that the average total arsenic concentration in agricultural soil is 50.26 mg/kg, which is 2.5 times higher than the maximum acceptable limit (20 mg/kg) recommended by the European Community. The natural portion of the arsenic concentration was larger than the anthropogenic portion. The high total arsenic concentration could be due to a combination of geogenic sources and irrigation with polluted groundwater. The average values of Igeo, Ipoll, and IB for agricultural soils were 1.10, 0.14, and 0.15, respectively; which are characterized as moderately polluted. The average non-carcinogenic hazard (HI) values for children and adults were 2.27 and 0.24, respectively, suggesting that children are exposed to non-carcinogenic risks. The total carcinogen risk (CR) value was 1.16E−04, which indicates a high risk of harmful effects to inhabitants.

Heavy Metals and Arsenic in Soils and Street Dust of the Southeastern Administrative District of Moscow: Long-Term Data

The soils and street dust of the Southeastern administrative district of Moscow were analyzed for chemical properties and the content of acid-soluble and mobile compounds of heavy metals (HMs) and arsenic over three time spans: the end of industrial (1995), transitional (2004 and 2012), and recent postindustrial (2017) periods of the city development. The acid–base properties of soils and street dust have not changed during this period. However, the content of exchangeable sodium has considerably increased (to 20-fold), as well as the contents of calcium and organic matter. The total HM and arsenic contents in soils and street dust tend to decrease because of a reduction in the number of industrial facilities and periodic replacement of lawn soils. Ag, Hg, Sb, Zn, and As have the highest clarkes of concentration in soils and Sb, Zn, Hg, Ag, Cu, Pb, Mo, As, Cd, Cr, and Ni, in street dust. The degree of extraction of the acid-soluble compounds of several HMs in soils and street dust is very high but it decreases from 1995 to 2017. The amount of mobile HM compounds has decreased. However, the share of soil and street dust samples with the Cu, Zn, and Pb mobile compounds exceeding the maximum permissible concentrations is still high.

Altered arsenic availability, uptake, and allocation in rice under elevated temperature

Climate change is expected to increase growing temperatures in rice cultivating regions worldwide. Recent research demonstrates that elevated temperature can increase arsenic concentrations in rice tissue, exacerbating an existing threat to rice quality and human health. However, the specific temperature-induced changes in the plant-soil system responsible for increased arsenic concentrations remain unclear and such knowledge is necessary to manage human dietary arsenic exposure in a warmer future. To elucidate these changes, we established four temperature treatments in climate-controlled growth chambers and grew rice plants (Oryza sativa cv. M206) in pots filled with Californian paddy soil with arsenic concentrations of 7.7 mg kg−1. The four chosen temperatures mimicked IPCC forecasting for Northern California, with a roughly 2.5 °C increase between treatments (nighttime temperatures ~2 °C cooler). We observed that arsenic concentrations in porewater, root iron plaque, and plant tissue increased in response to elevated temperature. There was a positive linear relationship between temperature and rice grain arsenic, almost all of which was present as inorganic As (III). Above-ground allocation patterns were consistent across treatments. We found no upregulation in the gene encoding the OsABCC1 transporter, believed to be important for arsenic sequestration in vacuoles and thereby preventing arsenic transfer to grain. Rice plants grown at higher temperatures had more adsorbed arsenic per unit of iron plaque (measured as [As]/[Fe]), indicating temperature may impact arsenic sorption to root plaque. We present evidence that increased soil mobilization of arsenic was the driving factor responsible for increased arsenic uptake into rice grain. Transpiration, which can increase arsenic transport to roots, was also heightened with elevated temperature but appeared to play a secondary role. Our system had low soil arsenic concentrations typical for California. Our findings highlight that elevated growing temperatures may increase the risk of dietary arsenic exposure in rice systems that were previously considered low risk.

Phytoremediation of a Highly Arsenic Polluted Site, Using Pteris vittata L. and Arbuscular Mycorrhizal Fungi.

Phytoremediation is a promising green technique for the restoration of a polluted environment, but there is often a gap between lab and field experiments. The fern, Pteris vittata L., can tolerate a high soil arsenic concentration and rapidly accumulate the metalloid in its fronds. Arbuscular mycorrhizal fungi (AMF) are mutualistic fungi that form a symbiosis with most land plants’ roots, improve their growth, and induce stress tolerance. This paper reports the results obtained using P. vittata inoculated with AMF, to extract Arsenic (As) from an industrial site highly contaminated also by other pollutants. Two experiments have been performed. In the first one, AMF colonized ferns were grown for two years under controlled conditions in soil coming from the metallurgic site. Positive effects on plant health and As phytoextraction and accumulation were detected. Then, considering these results, we performed a three year in situ experiment in the industrial site, to assess the remediation of As at two different depths. Our results show that the colonization of P. vittata with AMF improved the remediation process of As with a significant impact on the depth 0–0.2 m.

Analysis, spatial distribution and ecological risk assessment of arsenic and some heavy metals of agricultural soils, case study: South of Iran.

In this study, rates of arsenic, cadmium, chromium, copper, lead and zinc contents in agricultural soils from Eghlid County, south of Iran, were determined to assess the soil pollution and potential ecological risk index (PERI) and also spatial distribution of such elements. A total of 100 topsoil specimens were collected from 100 sampling stations. In the laboratory, after acid digestion the element contents in soil samples were determined using ICP-OES. Then, the soil contamination and also ecological risk of the soil were assessed using various indices especially Igeo, PI, IPI, PLI and PERI. Also, the spatial distribution maps of the studied elements in soil specimens were made using the kriging interpolation technique by ArcGIS software (10.4). Based on the results, the mean contents (mg/kg) of the elements in specimens were 1.85, 2.80, 19.04, 19.35, 7.17 and 38.77 for As, Cd, Cr, Cu, Pb and Zn, respectively. Arsenic and Cu contents were comparable to background values, while Cd contents were higher than their corresponding background values. The results of principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed that Cd had anthropogenic sources; while, other elements originated from natural sources. Pollution index (PI) values of As, Cd, Cr, Cu, Pb and Zn varied in the range of 0.45-1.49, 0.52-32.09, 0.096-0.33, 0.36-1.35, 0.18-0.32 and 0.23-1.59, with mean values of 0.92, 12.17, 0.21, 0.68, 0.21 and 0.96, respectively. The integrated pollution load index (PLI) values of the specimens with an average value of 0.84, indicated that 65% and 35% of soil samples were moderately and low contaminated, respectively. The mean value of PERI with 380.32 implied that the agricultural soils of the study area could be classified of high ecological risk. The spatial distribution of content of the elements showed that Cd had high spatial variability. Although in the short run, the contents of the elements found in the agricultural soil samples may not be alarming for agricultural production and consequently human health, signals it can be observed especially for Cd in the long term due to the impact of anthropogenic activities that lead to the discharge of this element to the environment and can result in its accumulation in agricultural soils. In conclusion, as it is expected that the metal inputs increase in the future, it is recommended that plant analyses be included in the future studies for determining the impact of the amount of bioavailable metals.

Estimation of Soil Arsenic Content with Hyperspectral Remote Sensing.

With the continuous application of arsenic-containing chemicals, arsenic pollution in soil has become a serious problem worldwide. The detection of arsenic pollution in soil is of great significance to the protection and restoration of soil. Hyperspectral remote sensing is able to effectively monitor heavy metal pollution in soil. However, due to the possible complex nonlinear relationship between soil arsenic (As) content and the spectrum and data redundancy, an estimation model with high efficiency and accuracy is urgently needed. In response to this situation, 62 samples and 27 samples were collected in Daye and Honghu, Hubei Province, respectively. Spectral measurement and physical and chemical analysis were performed in the laboratory to obtain the As content and spectral reflectance. After the continuum removal (CR) was performed, the stable competitive adaptive reweighting sampling algorithm coupled the successive projections algorithm (sCARS-SPA) was used for characteristic band selection, which effectively solves the problem of data redundancy and collinearity. Partial least squares regression (PLSR), radial basis function neural network (RBFNN), and shuffled frog leaping algorithm optimization of the RBFNN (SFLA-RBFNN) were established in the characteristic wavelengths to predict soil As content. These results show that the sCARS-SPA-SFLA-RBFNN model has the best universality and high prediction accuracy in different land-use types, which is a scientific and effective method for estimating the soil As content.

Arsenic in agro-ecosystems under anthropogenic pressure in Germany and France compared to a geogenic As region in Finland

Arsenic concentrations in soil and water were examined at the European level via a literature review and data inventory in the first phase of the AgriAs European Water JPI project. Arsenic in soil can be derived from both natural and anthropogenic sources. At the European scale, the distribution of arsenic in agricultural topsoil can mostly be explained by geology. In the next step, the AgriAs project investigated arsenic concentrations in soil and water in two regions: Saxony in Germany and Verdun in France. The results were compared with arsenic data from a geogenic arsenic region around the city of Tampere in Finland. In Saxony, arsenic is partly natural and partly derived from the widespread mining and ore processing activities in the area that have lasted for centuries. Areas contaminated with As were found to cover 970 km2 in Saxony. The soil baseline for As is only 20–40 mg/kg but the highest concentrations in soil are up to 5000 mg/kg. The large number of investigations in Saxony has given a possibility to evaluate As transfer into plants, fodder and food and to develop guidelines for farmers. In Verdun, arsenic is derived from a former chemical ammunition destruction facility that operated in the interwar period. Today, there are hot spots of As in topsoil with concentrations ranging from 100 to 1000 mg/kg, while the baseline concentration in soil is 18 mg/kg. In the Tampere region, baseline concentrations of As in glacial till forest soils are relatively high (30 mg/kg) over an area of 7400 km2, with hot spots of 1050 mg/kg in topsoil. However, agricultural soils contain clearly lower As concentrations. In all three regions, As concentrations in surface waters and in groundwater were found to be relatively low, and the As concentration in topsoil could not be linked to irrigation with As-containing water. Fortunately, As transfer from soil into plants via root systems is generally low in aerated soil, but As-containing dust can affect fodder plants. Especially in the Freiberg area of Saxony, As is usually associated with Cd contamination in topsoil, and guidelines for farmers based on Cd concentrations are also a good risk management method for As.

Heavy metals in the Arctic: Distribution and enrichment of five metals in Alaskan soils.

Metal contamination of food and water resources is a known public health issue in Arctic and sub-Arctic communities due to the proximity of many communities to mining and drilling sites. In addition, permafrost thaw may release heavy metals sequestered in previously frozen soils, potentially contaminating food and water resources by increasing the concentration of metals in freshwater, plants, and wildlife. Here we assess the enrichment of selected heavy metals in Alaskan soils by synthesizing publicly available data of soil metal concentrations. We analyzed data of soil concentrations of arsenic, chromium, mercury, nickel, and lead from over 1,000 samples available through the USGS Alaskan Geochemical Database to evaluate 1) the spatial distribution of sampling locations for soil metal analysis, 2) metal concentrations in soils from different land cover types and depths, and 3) the occurrence of soils in Alaska with elevated metal concentrations relative to other soils. We found substantial clustering of sample sites in the southwestern portion of Alaska in discontinuous and sporadic permafrost, while the continuous permafrost zone in Northern Alaska and the more populous Interior are severely understudied. Metal concentration varied by land cover type but lacked consistent patterns. Concentrations of chromium, mercury, and lead were higher in soils below 10 cm depth, however these deeper soils are under-sampled. Arsenic, chromium, mercury, nickel and lead concentrations exceeded average values for US soils by one standard deviation or more in 3.7% to 18.7% of the samples in this dataset. Our analysis highlights critical gaps that impede understanding of how heavy metals in thawing permafrost soils may become mobilized and increase exposure risk for Arctic communities.

Relationship of Arsenic and Lead in Soil with Fruit and Leaves of Apple Trees at Selected Orchards in Michigan

Historically, lead arsenate pesticides were commonly used in fruit orchards. Residues of metals from this historical use can persist in soil for decades, which can result in potential risk for humans if they consume fruits grown on contaminated soil. This research was conducted to assess lead and arsenic levels in apples, leaves, and orchard soil where the apples were grown to determine the relationship between metal levels in fruits and fruit products with those in orchard soil. Soil and tree tissue samples were collected from several Michigan farms, and metal concentrations were quantified by using microwave extraction and inductively coupled plasma mass spectrometry. Soil samples were collected at depths of 0 to 20 cm and 20 to 40 cm at a distance of 1 m from the tree trunk. Fruit samples also were processed into juice and pomace fractions to assess the partitioning of arsenic and lead during juice processing. The lead concentration was significantly higher in topsoil (9.4 μg/kg) compared with subsoil (6.9 μg/kg), but the arsenic content did not differ between the two soil layers (P > 0.05). Lead concentrations in apple leaves were correlated with lead in topsoil (0 to 20 cm; P = 0.03). Concentrations of total arsenic in all juice samples were less than 1 μg/kg and showed less potential than lead for uptake and translocation to fruits. There was no significant relationship between soil arsenic content and total arsenic concentrations in juice, pomace, and leaf samples (P > 0.05). Results of this research indicate that lead and total arsenic concentrations in apples and apple products from these selected orchards in Michigan are unlikely to be impacted by the contamination of these metals in orchard soil.

The migration dynamics and the speciation of arsenic in the Hetao area, Inner Mongolia.

Arsenic contamination of the groundwater in the Hetao area in Inner Mongolia, China, has been a serious problem since the 1980s. In this study, the behavioral mechanics of arsenic in soil in the Hetao area, in relation to arsenic concentrations in groundwater, were studied using elemental speciation analysis. It is for probing the possible mechanisms of correlation and interaction within water and soil of the area, which is little work on it not only in the Hetao area but also worldwide. Associated with our previous work on water in this area, soil samples were collected along transects through areas strongly affected by arsenic poisoning. Sequential extractions were used to determine the speciation in soil of arsenic and other elements (Cd, Cu, Mo, Pb, Sb, Sn, and Zn) which are with similar geochemical behaviors to arsenic in natural systems. The results show that the arsenic concentration in soil is correlated with arsenic concentration in groundwater. This implies that arsenic transformation as a main factor of the resident poisoning of the area could be related with groundwater and soil. These results suggest that arsenic poisoning in the Hetao area is related with water and soil. The tracers moving through water are retained in the shallow stratum including soil and persist in the water affected by the movement of arsenic through the shallow stratum and soil. Graphical abstract.

Development of Visible/Near-Infrared Hyperspectral Imaging for the Prediction of Total Arsenic Concentration in Soil

Soil total arsenic (TAs) contamination caused by human activities—such as mining, smelting, and agriculture—is a problem of global concern. Visible/near-infrared (VNIR), X-ray fluorescence spectroscopy (XRF), and laser-induced breakdown spectroscopy (LIBS) do not need too much sample preparation and utilization of chemicals to evaluate total arsenic (TAs) concentration in soil. VNIR with hyperspectral imaging has the potential to predict TAs concentration in soil. In this study, 59 soil samples were collected from the Daye City mining area of China, and hyperspectral imaging of the soil samples was undertaken using a visible/near-infrared hyperspectral imaging system (wavelength range 470–900 nm). Spectral preprocessing included standard normal variate (SNV) transformation, multivariate scatter correction (MSC), first derivative (FD) preprocessing, and second derivative (SD) preprocessing. Characteristic bands were then identified based on Spearman’s rank correlation coefficients. Four regression models were used for the modeling prediction: partial least squares regression (PLSR) (R2 = 0.71, RMSE = 0.48), support vector machine regression (SVMR) (R2 = 0.78, RMSE = 0.42), random forest (RF) (R2 = 0.78, RMSE = 0.42), and extremely randomized trees regression (ETR) (R2 = 0.81, RMSE = 0.38). The prediction results were compared with the results of atomic fluorescence spectrometry methods. In the prediction results of the models, the accuracy of ETR using FD preprocessing was the highest. The results confirmed that hyperspectral imaging combined with Spearman’s rank correlation with machine learning models can be used to estimate soil TAs content.

Status of arsenic accumulation in agricultural soils across China (1985–2016)

Based on 1677 published studies, 1648 sites across China collected from 1985 to 2016 were used to research the concentrations of arsenic in agricultural soils. In order to understand the status of arsenic pollution in agricultural soils in China over the past three decades, and to learn about the arsenic stocks in agricultural soils in various regions, and compared the relationship with annual arsenic emissions in China, and finally evaluated the potential ecological risks and human health risks. The median arsenic concentration in the surface agricultural soils of China was 10.40 mg Kg−1, and it ranged from 0.4 mg Kg−1 to 175.8 mg Kg−1. The inventory of arsenic in Chinese agricultural surface soils was estimated to be 3.71 × 106 t. In this study, the arsenic concentrations were found to be higher in Central, South, and Southwest China than those in other regions. The trend of arsenic pollution in agricultural soils has gradually increased over the past three decades. However, the growth rate of arsenic concentrations pollution in farmlands agricultural in China slowed during 2012–2016. The ecological risk index and geoaccumulation index revealed that arsenic in Chinese agricultural soil poses a low risk to the ecosystem. For human health assessment, the dietary pathway was the main pathway of exposure to arsenic in farmland soil of China. However, children's soil intake also contributed 34.48% to the exposure to arsenic, owing to their behavior. This study can provide a reference for the management of arsenic agricultural pollution in farmland soils in China.

ОЦЕНКА ТРАНСФОРМАЦИИ ПРИРОДНО-ТЕРРИТОРИАЛЬНЫХ КОМПЛЕКСОВ ПРИ ГОРНОПРОМЫШЛЕННОМ ТЕХНОГЕНЕЗЕ

Актуальность. Структуризация и формирование природно-территориальных комплексов происходит на протяжении длительного времени. За весь период преобразования и установления стабильно устойчивых территорий ландшафты претерпевают значительные изменения. Одним из факторов аналогичной трансформации является техногенная деятельность горнопромышленной отрасли, в связи с чем проводится оценка преобразованности, изучение процессов и схем преобразованности ландшафтов под действием техногенеза как одного из главных критериев, учитывающих месторасположение и расширение данных отраслей промышленности, что и обуславливает актуальность данной работы. Цель: произвести оценку экологической напряженности и видоизмененности ландшафтов, подверженных интенсивной техногенной нагрузке, в районе деятельности медеплавильного комбината. Объекты: компоненты ландшафтного комплекса и почвенный покров в районе интенсивной техногенной нагрузки, расположенные в окрестностях города Красноуральск, Свердловской области. Методы: оценка экологической напряженности территории; расчет коэффициента экологической защищенности ландшафтов по методике Б.И. Кочурова; расчет коэффициента радиальной дифференциации мышьяка в почвенном покрове в зоне интенсивной техногенной нагрузки. Результаты. Произведен анализ отдельных компонентов ландшафтных комплексов. Выявлены характеристики процессов видоизменения территорий, подверженных техногенной нагрузке. После расчетов коэффициента экологической стабильности по методике Б.И. Кочурова выявлено, что исследуемые ландшафты имеют острую экологическую ситуацию и обладают малой стабильностью. В качестве подтверждения техногенной нагрузки измерялась концентрация мышьяка в почвах исследуемых территорий, в результате чего зафиксированы превышения предельно допустимой концентрации в видоизмененных ландшафтах. В ходе подсчета коэффициента радиальной миграции мышьяка в почве объясняются процессы техногенной нагрузки.

Magnetic response of Arsenic pollution in a slag covered soil profile close to an abandoned tungsten mine, southern China

Previous studies indicated serious soil arsenic (As) pollution of large spatial extent related to tungsten mining. We performed systematic analyses of magnetic parameters and As contents of a slag covered soil profile close to the abandoned tungsten mine in southern China, in order to discuss the feasibility of using sensitive, non-destructive, and cost-effective magnetic methods for monitoring the soil arsenic content in such arsenic pollution areas. The results indicate that arsenic sulfide entered from slags into the underlying soil and changed to iron arsenate and moveable arsenic ion. The arsenic ions were transported from the upper to the lower part of the soil profile, leading to more serious arsenic pollution at lower levels of the section. Pedogenesis and oxidation of the entered iron and arsenic sulfide resulted in coexistence of magnetite/maghemite and hematite, with different contributions at depths of 125–195 cm, 60–125 cm, and 0–60 cm. The arsenic content is significant positively correlated with the hematite concentration given by the magnetic parameter HIRM and negatively correlated with the S−300 ratio that measures the relative contributions of magnetite(+maghemite) and hematite. The S−300 ratio is effective for semi-quantification of soil arsenic content, and may be also used for soil arsenic pollution assessment and monitoring in similar settings of tungsten mining.

Estimating Soil Arsenic Content with Visible and Near-Infrared Hyperspectral Reflectance

Soil arsenic (AS) contamination has attracted a great deal of attention because of its detrimental effects on environments and humans. AS and inorganic AS compounds have been classified as a class of carcinogens by the World Health Organization. In order to select a high-precision method for predicting the soil AS content using hyperspectral techniques, we collected 90 soil samples from six different land use types to obtain the soil AS content by chemical analysis and hyperspectral data based on an indoor hyperspectral experiment. A partial least squares regression (PLSR), a support vector regression (SVR), and a back propagation neural network (BPNN) were used to establish a relationship between the hyperspectral and the soil AS content to predict the soil AS content. In addition, the feasibility and modeling accuracy of different interval spectral resampling, different spectral pretreatment methods, feature bands, and full-band were compared and discussed to explore the best inversion method for estimating soil AS content by hyperspectral. The results show that 10 nm + second derivative (SD) + BPNN is the optimum method to predict soil AS content estimation; R v 2 is 0.846 and residual predictive deviation (RPD) is 2.536. These results can expand the representativeness and practicability of the model to a certain extent and provide a scientific basis and technical reference for soil pollution monitoring.

Effects of exogenous arsenic stress on bacterial and archaeal communities in two types of soils

Mining, smelting and other activities result in arsenic accumulation in soils, with adverse impacts on the quality and safety of agricultural products and soil microorganisms. We monitored the changes of available arsenic content with incubation time after the addition of exogenous arsenic to the yellow soil (YS) and soil derived from purple sandy shale (RS). The community changes of bacteria and archaea in soils without spiked arsenic and soils after 1, 30 and 360 days of exogenous arsenic stress were measured by MiSeq high-throughput sequencing, to investigate the community adaptative mechanism of bacteria and archaea in soil under arsenic stress. Results showed that the available arsenic content in soils decreased gradually with time, which significantly affected the composition of soil bacteria and archaea community. The abundance of dominant bacterial group changed significantly, whereas only archaea with lower abundance changed obviously, and little change occurred in dominant archaea group, indicating that archaea community had high arsenic tolerance and stability. Compared with the arsenic stress time, soil arsenic availability had greater impacts on community structures of bacteria and archaea. The results could provide refe-rences for safe utilization and microbial remediation of arsenic-contaminated cropland.