Soil Quality Standards Research Articles

Classification and regression tree (CART) for predicting cadmium (Cd) uptake by rice (Oryza sativa L.) and its application to derive soil Cd threshold based on field data

The entry of Cd into soil-rice systems is a growing concern as it can pose potential risks to public health. To derive regional soil Cd threshold, a total of 333 paired soil and rice samples was collected in Anhui Province, Eastern China. The results showed that the total soil Cd and soil Zn/Cd were the most significant variables contributing to Cd content in polished rice. The Chinese Soil Quality Standards might overestimate risk posed by Cd-contaminated soil for rice production in the mining area due to high Zn/Cd values of some mining-associated soils. Cd levels in polished rice can be predictable using stepwise multiple linear regression (MLR) model. However, the derived soil Cd threshold based on the MLR model would be unrealistically high. The classification and regression tree method (CART) performed well in simulating Cd levels in polished rice and can be used to derive soil Cd threshold instead of MLR to minimize the uncertainty.

Predicting soil ecological criteria of 17 metal(loid)s in China based on quantitative ion character-activity relationship - Species sensitivity distribution (QICAR-SSD) coupled model

Soil pollution caused by metal(loid)s is increasingly serious and poses unexpected risks to terrestrial organisms. Establishing soil quality standards is essential for assessing ecological risks of metal(loid)s and protecting soil ecosystems. However, the limited availability of metal(loid) ecotoxicological data has hampered the development of soil quality standards due to financial and practical constraints on toxicity testing. This study collected 77 normalization equations and 58 cross-species extrapolation equations to calculate the normalized EC10 (the added concentration causing a 10 % inhibition effect) of metal(loid)s under a representative scenario. A set of quantitative ion character-activity relationship (QICAR) models were then constructed using normalized EC10 and nine critical ionic characters (AR, AR/AW, BP, MP, Z/r2, Z/r, Xm, σp, and |Log(KOH)|). Subsequently, these QICAR models were employed to predict ecotoxicological EC10 of 17 metal(loid)s to 12 soil species and coupled with species sensitivity distribution (SSD) to determine Predicted No Effect Concentration (PNEC). The results demonstrated the coupled QICAR-SSD model could effectively derive terrestrial PNEC for data-poor metal(loid)s, with errors between the predicted PNEC and reported soil standards (excluding soil background levels) from different countries mostly <0.3 orders of magnitude. Finally, soil ecological criteria (SEC) for 17 metal(loid)s were calculated using an added risk approach based on PNEC and national soil background concentration. Overall, the coupled model proposed here can provide a valuable supplement to the development of soil quality standards for numerous metal(loid)s in soil components.

Cd mobilization in mining-impacted soils with different bedrock lithology: Insights from stable Cd isotopes

The environmental risk of Cd in soils strongly depends on the mobilization of Cd in soils. However, limited knowledge exists on the redistribution of exogenic Cd inputs in soils, especially across diverse lithological regions. Herein, we aimed to investigate the fate of Cd in soils from two mining areas with contrasting lithologies (siliceous and calcareous) using stable Cd isotopes. The isotope tracing results confirm that mining activities are the main Cd source in both areas. The positive correlation between δ114/110Cd values and goethite/dolomite content indicates the release of heavy Cd isotopes during the dissolution of exogenetic minerals. Additionally, high contents of exchangeable Cd (11 % to 36 %) and Fe oxide-bound Cd (29 % to 42 %) drive plant pumps to transport heavy Cd isotopes from the deeper to upper horizons of the soils from the siliceous area. In the calcareous area, the total organic carbon content is positively correlated with the Cd concentration and δ114/110Cd value, suggesting potential complexation of Cd with organic matter due to the stabilizing effect of carbonate minerals on soil organic matter. This study highlights the different redistributions of exogenous Cd in soils from diverse lithological regions, emphasizing the need to consider regional lithology when developing soil quality standards for Cd.

A screening model for predicting the potential of soil colloids-enhanced leaching of hydrophobic organic contaminants to groundwater at contaminated sites

Modeling the fate and transport of organic pollutants at contaminated sites is critical for risk assessment and management practices, such as establishing realistic cleanup standards or remediation endpoints. Against the conventional wisdom that highly hydrophobic persistent organic pollutants (POPs) (e.g., polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons) in surface soils are essentially immobile, mounting evidence has demonstrated the potential of these contaminants leaching into the groundwater, due to enhanced transport by soil colloids. Here, we develop a Colloids-Enhanced Transport (CET) model, which can be used as a simple screening tool to predict the leaching potential of POPs into groundwater, as mediated by soil colloids. The CET model incorporates several processes, including the release of POPs-bearing colloids into the porewater, the vertical transport of colloids and associated POPs in the vadose zone, the mixing of POPs-containing soil leachate with groundwater, and the migration of POPs-bearing colloids in saturated zone. Thus, using parameters that can be easily obtained (e.g., annual rainfall, soil type, and common hydrogeological properties of the subsurface porous media), the CET model can estimate the concentrations of POPs in the saturated zone from the observed POPs concentrations in surface or shallow subsurface zones. The CET model can also be used to derive soil quality standards or cleanup endpoints by back-calculating soil concentrations based on groundwater protection limits.

Urban green space area mitigates the accumulation of heavy metals in urban soils

Despite that the heavy metals in urban soils pose a threat to public health, the critical factors that influence their concentrations in urban soils are not well understood. In this study, we conducted a survey of surface soil samples from urban green spaces in Shanghai, to analyze the concentrations of the key heavy metals. The results showed that Zn was the most abundant metal with an average concentration of 122.99 mg kg−1, followed by Pb (32.72 mg kg−1) and Cd (0.23 mg kg−1). All concentrations were found to be below the risk screening values defined by the National Environmental Quality Standards for soils of development land in China (GB36600-2018), indicating no current risk in Shanghai. However, there was a clear accumulation of heavy metals, as the mean concentrations were significantly higher than the background values. Furthermore, we explored the relationships between key heavy metals with population density, GDP and green space area. Both Spearman correlation and Random Forest analysis indicated that per capita green space area (pGSA) and population density were the most crucial factors influencing the status of heavy metals in urban soils, unlike edaphic factors e.g. SOM content in farmland soils. Specifically, there was a significantly positive linear correlation between heavy metal concentrations and population density, with correlation coefficients ranging from 0.3 to 0.4. However, the correlation with pGSA was found to be non-linear. The nonlinear regression analysis revealed threshold values between heavy metals concentrations and pGSA (e.g Zn 22.22 m2, Pb 24.92 m2, and Cd 25.92 m2), with a sharp reduction in heavy metal concentrations below the threshold and a slow reduction above the threshold. It suggests that an increase in per capita green space area can mitigate the accumulation of heavy metals caused by growing population density, but the effect is limited after the threshold. Our findings not only provide insights into the distribution patterns of heavy metals in the urban soils at the local scale, but also contribute to the urban greening at the global scale and offer guidance for city planning in the face of increasing population densities over the coming decades.

Spatial distribution and health risk assessment of toxic metal(oid)s in soils of coal mining areas of the Salt Range, Punjab, Pakistan

Long-term coal mining operations have been linked to increases in HM concentrations in subterranean soils, which degrades soil quality. The clusters of coal mines and mine tailings considerably increase metal(loid)s concentrations in the surrounding soils and air of the Eastern (ESR), Central (CSR), and Trans-Indus Salt Range (TSR). The present study was conducted in this scenario to ascertain the occurrence and dispersion of toxic metals from mine tailings to different environmental components and their pollution load in soils and possible risk. The geochemical characterization of the soil, coal waste, and dust particulate matter revealed that waste samples are highly enriched in As, Cd, Pb, Fe, and Zn. In terms of soil quality standards, geo-accumulation index (Igeo), enrichment factor (EF), and contamination factor (CF), Fe, Mn, and Zn are extremely contaminated. However, As, Cd, Co, and Cr show moderate contamination. These harmful soil contaminants, primarily originate from coal-associated tailings. Further, the principal component analysis, multiple linear regression (PCA-MLR), and agglomerative hierarchical clustering (AHC) signify that mineralization and weathering of sulfide and carbonate minerals within the coal wastes and lithological units of the present study area cause the release of environmentally sensitive trace elements, which upon dispersion, leaching, and atmospheric deposition enters the air and soils of the present study area. We propose that higher HI index of Co (4), Fe (35), Mn (11), and Zn (13) values can be a significant human health concern.

Optimizing the development of contaminated land in China: Exploring machine-learning to identify risk markers

Often available for use, previously developed land, which includes residential and commercial/industrial areas, presents a significant challenge due to the risk to human health. China's 2018 release of health risk assessment standards for land reuse aimed to bridge this gap in soil quality standards. Despite this, the absence of representative indicators strains risk managers economically and operationally. We improved China's land redevelopment approach by leveraging a dataset of 297,275 soil samples from 352 contaminated sites, employing machine learning. Our method incorporating soil quality standards from seven countries to discern patterns for establishing a cost-effective evaluative framework. Our research findings demonstrated that detection costs could be curtailed by 60% while maintaining consistency with international soil standards (prediction accuracy = 90–98%). Our findings deepen insights into soil pollution, proposing a more efficient risk assessment system for land redevelopment, addressing the current dearth of expertise in evaluating land development in China.

Identifikasi Karakteristik Mineral Magnetik Berdasarkan Analisis XRF di Lahan Pertanian Sekitar Sungai Biyonga Kabupaten Gorontalo

An analysis of soil chemical elements using X-Ray Fluorescence (XRF) has been conducted on paddy fields in Dutulanaa Village, Gorontalo Regency, and corn farms in Polohungo Village, Gorontalo Regency. Soil samples were taken at three locations, namely corn location 1 (location I), corn location 2 (location II), and paddy fields (location III). At each location, samples were taken at 2 points to obtain 6 pieces. The distance between sampling points is 10 m. Based on the results of XRF measurements, the elements that dominate in paddy fields and corn include silica (Si), iron (Fe), aluminum (Al), calcium (Ca), titanium (Ti), potassium (K), and manganese (Mn), where Si is a diamagnetic element, Fe is a ferromagnetic element, and Al, Ca, Ti, and K are paramagnetic elements. The most significant percentage is silica (Si), 60.27% in corn soil 2 points J2T2. The next highest element is iron (Fe), 29.47% in corn soil, 1 point J1T2. The next element is aluminum (Al), 9.10% in corn soil at 1 point J1T1, calcium (Ca) in corn soil at 2 points J2T2 is 10.03 %, titanium (Ti) was 2.31% in paddy fields at ST5 point and potassium (K) was 2.31% in a paddy field at ST5 point, and the lowest value was manganese (Mn) of 0.59% in corn soil 2 points J2T1. Even some heavy metal elements, such as lead (Pb), were found—zinc (Zn) and manganese (Mn). The highest heavy metal elements were found in agricultural corn land at 2 J2T2 points, namely lead (Pb) at 158 ppm, zinc (Zn) at 4,555 ppm, and manganese (Mn) at 17,100 ppm, where these results have exceeded the threshold of soil quality standards, resulting in environmental pollution of agricultural land.

Accumulation and Transport of Phthalic Acid Esters in the Soil-Plant System of Agricultural Fields with Different Years of Film Mulching

In this study, we investigated the accumulation and transport patterns of phthalate ester (PAEs) compounds in the soil-plant system of maize and cabbage fields under different film mulching years. The total content of five PAEs in the maize fields soil ranged from 156.19 to 566.1 μg kg−1 with film mulching for 0–20 years. The total content of five PAEs in the cabbage field soils ranged from 252.48 to 559.07 μg kg−1 with film mulching for 0–30 years. The PAEs content in cabbage and maize field soils was lower than the environmental quality standards for soil (GB 15618-2008). With the increase in film mulching years, both maize and cabbage soil PAEs contents increased significantly (p &lt; 0.05), while among the five PAEs, the contents of di-n-butyl phthalate (DnBP) and di(2-ethylhexyl) phthalate (DEHP) increased the most significantly, and the content of DEHP in the soils was the highest. The DEHP content in soils planted with maize ranges from 134.03 to 406.79 μg kg−1 with the film mulching for 20 years; while in soil planted with cabbage, it ranges from 229.35 to 405.2 μg kg−1 with the film mulching for 30 years. The DEHP content in all of the soils has not exceed the limit value established by the USEPA in U.S. Five PAEs were detected in maize seeds and cabbage leaves, among which the DEHP content exceeded the maximum residue limit set by the National Food Safety Standard (GB 9685-2016) for DEHP in food after more than 10 years of mulching. The bioaccumulation and translocation factors in cabbage showed a significant positive correlation with the film mulching years. However, the bioaccumulation factor and translocation factor in maize have weak correlations with the film mulching years, possibly due to the lower PAEs content in the deep soil layers where maize roots are distributed. Our research revealed a significant association between the presence and distribution of PAEs in crops and mulching years. These novel discoveries provide fundamental information for controlling PAEs pollution in agricultural environments.

Soil heavy metal pollution from waste electrical and electronic equipment of repair and junk shops in southern Thailand and their ecological risk

The waste electrical and electronic equipment (WEEE) stream in Thailand shifted from exporting WEEE to recycling them in domestic enterprises after China's import restrictions on e-waste in 2018. This study aims to investigate the pollution status, pollution sources, and ecological risk of heavy metals from manual WEEE dismantling facilities (12 repair shops and 8 junk shops) in the Nakhon Si Thammarat province of southern Thailand by examining the concentrations of As, Cd, Ni, and Pb in the topsoil (0–15 cm) during the wet and dry seasons. The results revealed that the mean concentrations of all heavy metals were higher during the dry season than in the wet season. The concentrations of analyzed soil heavy metals decreased as the intensity of e-waste dismantling activities increased, with recycling sites > repair sites > control sites (no e-waste recycling activities). Only 10% of WEEE processing workshops (junk shops) had soil Pb and As concentrations that exceeded Thailand's residential soil quality standards. However, ecological indexing models based on the geo-accumulation index found that 75% of electric repair shops were contaminated with the analyzed heavy metals, particularly Pb. Moreover, the Nemerow integrated pollution index indicated that 16.7% of electric repair shops were on the pollution warning line. Our findings suggest that policymakers should promote ecological risk assessment as a method for mitigating the negative environmental impact of electronic repair businesses, which are widely dispersed in residential areas and tend to dominate the WEEE stream because of the circular economy concept of “right to repair”, and highlight the decline of junk shops and e-waste dismantling villages for waste export resulting from China's ban.

Application of machine learning and multivariate approaches for source apportionment and risks of hazardous elements in the cropland soils near industrial areas in Bangladesh

Quick industrial and urban development accelerates the hazardous elements (HEs) content in agricultural soil which is a matter of concern for ecological and public health. This present study investigates the HEs content (As, Pb, Cd, Cr, Ni, and Cu) in agricultural fields near industrial areas of Bangladesh to assess the metal concentration, distribution, sources apportionment, and their probable ecological and human health impacts using an integrated approach of machine learning and multivariate indices. Principal component analysis (PCA) showed about 28.9% of spatial variation of HEs in the study area. Metal concentrations were compared to international soil quality standards (ISQSs) and found that Cd, Ni, and Cu exceeded the ISQSs while about 80% and 100% of samples surpassed the Toxic reference value for Cd, Cr, Ni, and Cu, respectively. All HEs contents exceeded the background value excluding As. According to Positive matrix factorization (PMF) analysis, three possible sources controlled HEs content in the study area: (i) anthropogenic (Cd; 79%); (ii) mixed sources (Cu; 76%), (Ni; 51%), (Cr; 48%), and (As; 39%); and (iii) atmospheric fallout (Pb; 67%), that is corresponding by self-organizing map (SOM), and random forest (RF). The pollution load index indicated that about 77% area was polluted by studied HEs. Additionally, other pollution evolution indices including mean Effect Range Median quotient (0.31 ± 0.05), Nemerow pollution index (2.64 ± 1.13), Degree of contamination (8.20 ± 2.16), and Modified hazard quotient (1.69 ± 0.19), exhibited moderate contamination of HEs in soil samples. Based on ecological risk about 20–53% of samples were moderate to high risk, while the descending order of HEs was Cd > Pb > Ni > As > Cr > Cu. For the public health aspect, no significant non-carcinogenic health risks (THI < 1) for adults (female = 1.03E-01 and male = 9.50E-02) and children (6.83E-01), while moderate carcinogenic health risks for adults (female = 2.65E-05and male = 2.36E-05), and children (4.37E-05). Overall, this study area soils are polluted with HEs mainly by anthropogenic activities, which have significant health hazards for the inhabitants.

Assessment of roadside pollution by heavy metals: A case study from the District of Bani Kinanah, Irbid, Northern Jordan.

The District of Bani Kenanah is home to natural reserves, forests, local agricultural practices, and a multitude of historical and cultural sites. The majority of the population in the study area is employed in the agricultural sector, which is dominated by olive tree cultivation and the production of premium olive oil. The current study aimed to assess the degree of roadside soil pollution and predict the potential ecological impacts of Pb, Cd, Zn, Cr, Ni, Mn, Cu, Fe, and Co. Therefore, 30 soil samples were collected and analyzed with a Flame atomic absorption spectrophotometer for the aforementioned metals. The spatial distribution maps of these metals were generated by inverse distance weighted (IDW) interpolation in ArcGIS 10.3. The values of heavy metals (HMs) in the study were lower than the international standards for soil quality. The soil was classified as moderately to substantially enriched with Cd, Pb, and Zn based on the EF values. However, the indices of geo-accumulation (Igeo), contamination factor (CF), and potential ecological risk (RI) generally revealed minor metallic contamination. The traffic and agricultural activities were the potential sources of Cd, Pb, and Zn in the study area. Incorporating HMs analysis with GIS maps was beneficial for assessing soil pollution.

STUDY OF THE DISCIPLINE "NORMATION OF ANTHROPOGENIC LOAD ON THE NATURAL ENVIRONMENT" AS THE BASIS OF TRAINING STUDENTS FOR ECOLOGY 101

The regulation of anthropogenic load on the environment is an important problem in the modern world, since human activity significantly affects nature and can lead to serious environmental problems. In order to reduce the negative impact on the environment, it is necessary to establish norms and limits on the level of anthropogenic load.&#x0D; The moderation of anthropogenic load on the environment is an important topic for environmental students who study the impact of human activities on natural ecosystems.&#x0D; For environmental students, it is necessary to know the principles and methods of normalization of anthropogenic load, as well as to understand what types of activities can have a negative impact on the environment and how this impact can be reduced. They must be familiar with air, water, and soil quality standards, and know how to measure and monitor pollution levels. In addition, environmental students need to understand that the regulation of anthropogenic load is only one of the ways to reduce the negative impact of human activity on the environment.&#x0D; In order for the normalization of anthropogenic load to be effective, it is necessary to ensure many factors, such as types of damage, their sources, geographical and climatic conditions, and other factors that affect the distribution and concentration of pollutants in the environment. Therefore, the anthropogenic load should be regulated taking into account the specific conditions of the area and the type of activity.&#x0D; Limitation of anthropogenic load plays an important role in ensuring sustainable development and preservation of natural resources. The use of air, water and soil quality standards ensures the safety and health of the population, preserves biodiversity and natural ecosystems, and reduces the impact of human activity on the climate.

Generalizable consistency of soil quality standards for pesticides: Modeling perspectives

Soil quality standards for pesticides play a crucial role in protecting plants and preventing potential health hazards to humans. Here we discuss modeling approaches to define pesticide soil quality standards from two effect endpoints, which ensures consistency throughout the entire pesticide life cycle from application to human exposure assessment. Given that pesticides are applied in a pulse-like emission pattern and their soil concentrations change over time, both a ceiling legal limit and an average legal limit for pesticide soil quality standards should apply to the initial pesticide application practice and the potential human health effect. The timing intervals for pesticide application and the dissipation half-life in the soil can be used to quantify the relationship between the ceiling and average legal limits. By analyzing primary exposure pathways related to soil contamination, the average legal limit can be linked to theoretical human health risks, which requires a comprehensive evaluation for an adequate safety margin, including human interactions with soil, exposure assessment of soil pesticides, and allocation exposure assessment. To establish acceptable human health risks, the average legal limit can be determined, and the ceiling legal limit can be estimated based on the quantitative relationship between the ceiling and average legal limits. Additionally, we discuss situation-specific factors, including climate-pattern and behavior-pattern factors, to define pesticide soil quality standards to further complete the modeling framework. We hope insights presented in this paper will assist regulatory agencies worldwide in defining pesticide soil quality standards that meet their specific regulatory needs throughout the entire pesticide life cycle.

Significant urban hotspots of atmospheric trace element deposition and potential effects on urban soil pollution in China

Rapid urbanization has profoundly altered the spatial patterns of multiple element cycles. Whether and how urbanization shapes the spatial patterns of atmospheric trace element deposition remains, however, poorly understood. Using a newly compiled database on bulk deposition of eight trace elements (i.e., Cu, Ni, Zn, As, Cd, Cr, Hg and Pb) in China, we assessed the urban imprints on the spatial patterns of trace element deposition. Bulk deposition of the eight trace elements all showed a significant increase with closer distance to the nearest large cities, while the urban effect was also mediated by point emission sources and precipitation. We further compiled a database of urban topsoil (0–10 cm) concentrations of the eight trace elements and found that urban soil quality standards were exceeded in 80% of the studied cities for Cr, 49% for As, and less than 25% for other trace elements, respectively. The urban topsoil concentrations of six trace elements (except As and Hg) showed no significant correlations with their background values for natural soils, while we found a significant correlation between bulk deposition and urban topsoil concentrations of trace elements corrected by background values. We also demonstrated that current levels of trace element deposition would substantially increase urban soil pollution over the coming decades. Our findings confirm the occurrence of urban hotspots of trace element deposition and their impact on soil pollution and highlight a need of emission control of trace elements for safety urban soil quality.

Accumulation of Cr in different vegetables and derivation of soil Cr threshold using the species sensitivity distribution method

Due to its high mobility and bioavailability, hexavalent chromium [Cr(VI)] in agricultural soil can be taken up by crops and pose threat to human being. In this study, two soils (Jiangxi red soil and Shandong fluvo-aquic soil) spiked with Cr(VI) and 8 common vegetable varieties were used to conduct the pot experiment. The bioconcentration factor (BCF) values based on the tetraacetic acid extractable Cr (EDTA-Cr) in soils were used to construct the species sensitivity distribution (SSD) curve. Afterwards, the soil Cr threshold was derived based on the critical BCF value and the permissible limit of Cr for vegetables. The results showed that when spiked with 5.6 mg kg−1 of Cr(Ⅵ), the soil EDTA-Cr concentrations were significantly increased compared with the control except Jiangxi red soil planted with carrot and radish, while the Cr concentrations in the edible parts of vegetables in both soils were below the permissible limit (0.5 mg kg−1 FW). However, there are dramatic differences in the accumulation of Cr by different varieties of vegetables. Apparent discrepancy was observed between the two soils for the bioconcentration of Cr by carrot. Among the leafy vegetables, lettuce and oilseed rape are the most and the least sensitive to Cr pollution, respectively. The safety threshold values of EDTA-Cr were 0.70 mg kg−1 for Shandong fluvo-aquic soil and 0.85 mg kg−1 for Jiangxi red soil, respectively. This study provides information on the safety production of vegetable products in Cr(Ⅵ) polluted soils and is helpful to the revision of soil quality standards of Cr.

Analysis of productivity levels of saline coastal land for crop cultivation activities

Saline land is an area zone that is widely developed for agribusiness activities with high economic value. The purpose of this study is to determine the parameters that affect the level of productivity of saline land in coastal areas for agricultural agribusiness activities. The research methods used were descriptive quantitative and descriptive qualitative methods. The indicators observed were soil and water parameters on saline land. The results showed that soil parameters that are not following the quality standards of agricultural cultivation are N 0.12-0.14%, P2O5 14-57 mg/L, K2O 473-506 mg/L, Ca 0.47-1.27%, Mg 0.51-5.14%, Al 8.51-243%, and Na 0-0.37%. Water parameters that do not comply with agricultural cultivation quality standards are Ca 54.02-320.60 mg/L, Mg 78.22-424.94 mg/L, Na 582.31-3208.68 mg/L, PO4 0.11-0.72 mg/L. Y= 18.021+0.80X1+0.262X2+0.332X3+0.081X4+0.105X5+0.177X6+0.794X7 Is formula of soil regression test resulted. Meaning that parameters that do not meet soil quality standards will simultaneously affect the land productivity. The water regression model formula by Y= 7890+0.001X1+0.002X2+0.003X3+0.004X4, means that water quality parameters that do not comply with quality standards do not affect the level of land productivity. The results of the dynamic analysis estimate that the level of productivity and carrying capacity of land in saline coastal areas will decrease along with the increase in crop yields. Based on the study of modelling analysis, it can be concluded that there are several soil parameters such as N, P2O5, K2O, Ca, Mg, Al, and Na that affect the productivity level of saline land in coastal areas.

Effects of anthropogenic and natural environmental factors on the spatial distribution of trace elements in agricultural soils

The concentrations of trace elements in agricultural soils directly affect the ecological security and quality of agricultural products. A comprehensive study aimed at quantitatively analyze the effects of anthropogenic and natural environmental factors on the spatial distribution of heavy metals (HMs) and selenium (Se) in agricultural soils in a typical grain producing area of China. Factors considered in this study were parent rock, soil physicochemical properties, topography, precipitation, mine activity, and vegetation. Results showed that the median values of Zn, Cd, Cr, and Cu of 111 topsoil samples exceeded the background values of Guangxi province but were lower than the relevant national soil quality standards, and 85% of soil samples were classified as having rich Se levels (0.40 −3.0 mg kg−1). The potential ecological risk index of soil heavy metals as a whole was low, with Cd in 9% of the samples posing moderate ecological risk. The concentrations of heavy metals and Se were relatively high in soils from shale rock. Soil properties, mainly Fe2O3 and Mn played a dominant role on soil HMs and Se concentrations. Based on GeoDetector, we found that the interaction effects of two factors on the spatial differentiation of soil HMs and Se were greater than their sum effect. Among the factors, Mn enhanced the explanatory power of the model the most when interacting with other factors for soil Zn; the greatest interactive effect was between distance from mining area and Mn for Cd (q = 0.70); Fe2O3 significantly promoted the spatial differentiation of soil Cr, Cu and Se when interacting with other factors (q > 0.50). These findings contribute to a better understanding of the factors that drive the distribution of HMs and Se in agricultural soils.

Tracing and quantifying the source of heavy metals in agricultural soils in a coal gangue stacking area: Insights from isotope fingerprints and receptor models

Historic coal gangue stacking probably brings heavy metals (HMs) into the surrounding agricultural soil, posing potential harm to human and environmental health. For better controlling and preventing agricultural soil HMs pollution, the screening of priority pollutants and identification of their pollution pathways are urgent in coal gangue stacking areas. Thus, this study selected a coal gangue stacking area in Chongqing, China as the research object and conducted the pollution evaluation, spatial distribution and source apportionment of the HMs (Cd, Cr, Ni, Cu, Zn, As, Pb and Hg) in surrounding agricultural soil. Results showed that the soil was moderately to heavily contaminated by Cd with average concentrations of 1.23 mg/kg, which were 4.1 times higher than the Environmental Quality Standards for Soils of China. Cd was considered as the soil precedent-controlled pollutant in this study area and subsequent soil δ114/110Cd values indicated that Cd in surface soils primarily originated from the leachate of coal gangue stacking, which contributed about 89.9 % and 85.47 % to the total soil Cd according to the absolute principal component scores-multiple linear regression model (APCS-MLR) and positive matrix factorization model (PMF), respectively. In addition, other HMs mainly resulted from the leachate of coal gangue, natural and agricultural mixed pollution as well as traffic pollution. Therefore, this study provided basic information for pollution control of the HMs in agricultural soil in the coal gangue stacking area.

Contamination, Source Apportionment, and Health Risk Assessment of Heavy Metals in Farmland Soils Surrounding a Typical Copper Tailings Pond.

Tailings resulting from mining and smelting activities may cause soil heavy-metal pollution and harm human health. To evaluate the environmental impact of heavy metals from tailings on farmland soils in the surrounding area, heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) in tailings and farmland soils in the vicinity of a typical copper tailings pond were analyzed. Contamination status, potential sources, and health risks for farmland soils were investigated. The results showed that the tailings contained a high concentration of Cu (1136.23 mg/kg). The concentrations of Cd and Cu in the farmland soils exceeded the soil quality standard. The geoaccumulation index (Igeo) indicated that the soils were moderately polluted by Cu and Cd, and slightly polluted by Ni, Cr, and Zn. The absolute principal component scores-multiple linear regression (APCS-MLR) model was applied for source apportionment. The results showed that tailings release is the main source of soil heavy-metals contamination, accounting for 35.81%, followed by agricultural activities (19.41%) and traffic emission (16.31%). The health risk assessment suggested that the children in the study region were exposed to non-carcinogenic risks caused by As, while the non-carcinogenic risk to adults and the carcinogenic risk to both adults and children were at acceptable levels. It is necessary to take effective measures to control heavy-metal contamination from tailings releases to protect humans, especially children, from adverse health risks.