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Selenium (Se) has a dual nature, with beneficial and harmful effects on plants, essential for both humans and animals, playing a crucial role in ecosystem regulation. Insufficient Se in specific terrestrial environments raises concerns due to its potential to cause diseases, while excess Se can lead to severe toxicity. Thus, maintaining an optimal Se level is essential for living organisms. This review focuses first on Se transformation, speciation, and geochemical properties in soil, and then provides a concise overview of Se distribution in Chinese soil and crops, with a focus on the relationship between soil Se levels and parent materials. Additionally, this paper explores Se bioavailability, considering parent materials and soil physicochemical properties, using partial least squares path modeling for analysis. This paper aimed to be a valuable resource for effectively managing Se-enriched soil resources, contributing to a better understanding of Se role in ecosystems., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Land-use change influences the fate of nutrient elements, including iron (Fe), and then threaten soil security. In this study, Fe forms and stable isotope composition (δ 56 Fe) in soils were investigated to identify the variations in the processes of Fe cycling during agricultural abandonment in a karst region of Southwest China. Soil δ 56 Fe compositions varied from -0.05‰-0.02‰ in croplands, 0.05‰-0.12‰ in abandoned croplands, to 0.30‰-0.80‰ in the native vegetation lands. In the croplands, Fe oxidation-precipitation process is considered as the main contributor to Fe migration and isotope fractionation, leading to a relatively enrichment of heavier Fe isotope in deeper soil layer. In the abandoned croplands and native vegetation lands, Fe isotope in the organic-rich layer (0-10 cm) was significantly lighter than that in subsurface layer (20-30 cm), mainly due to the recovery of soil organic carbon (SOC) and macro-aggregate after cropland abandonment. Moreover, the eluviation process mainly caused a decrease in soil Fe contents and enrichment of heavy Fe isotope in deeper soils (below 40 cm). The positive correlation between oxidized Fe and SOC contents suggested the accumulation of mobile Fe in soils after agricultural abandonment, which is beneficial for Fe uptake and assimilation by plants. This study suggests that agricultural abandonment significantly reduce soil Fe leaching loss and improve plant Fe supply by SOC accumulation in surface soil, which gives an environmental implication for the management of soil nutrients., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The effects of topography, land cover type, and soil physicochemical properties on the distribution of soil organic carbon (SOC) and total nitrogen (TN) have drawn growing attention recently, but little is known about how these features-associated interactions impact SOC and TN. To elucidate how these interactions affect the preservation of carbon and nitrogen in soils, we used data-driven models (random forest regression and structural equation modeling) to identify the dominant environmental factors affecting the distribution of SOC and TN in two different soil layers (0-20 and 20-40 cm) of the Qinghai-Tibet plateau. In addition, an algorithm based on random forest ("Boruta") was chosen to identify the relevant influencing factors and partial dependence was used to depict the two most important factors. We found that rather than land cover type, environmental properties, such as soil physicochemical characteristics and altitude had the most significant effects on the distribution of SOC and TN. Our findings indicate that elevation and TN are the two most important factors influencing SOC in the surface and subsurface soil layers. Moreover, total potassium (TK) impacts TN content in the surface soil layer, but only in a specific range of concentrations, which could be attributed to anthropogenic activities such as applying nitrogen and potassium fertilizers to increase the yields of local food crop, Tibetan hulless barley. These findings provide a scientific perspective on soil nutrient preservation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Biochar can significantly enhance soil organic carbon (SOC) and crop yield, and it is therefore the preferred material for soil improvement in medium-low yield fields. In this study, a field experiment was designed to explore the impacts of biochar application on SOC content and fraction composition. Results indicated that incorporation of biochar into soil increased the SOC content by 26.9%-65.3% in the surface layer (0-10 cm) and 30.3%-63.0% in the subsurface layer (10-20 cm) of soil, while water-soluble organic carbon (WSOC) of the two layers was increased by 2.2-40.0% and 2.3-39.8%, respectively. Microbial biomass carbon decreased under conventional nitrogen treatments and increased with biochar addition under increased nitrogen application. The C:N value increased with biochar application, while the water-soluble C:N value of soil applied with 30 t ha -1 biochar was lower than that of soil applied with 15 t ha -1 biochar, both in the two tested soil layers. Wheat yield is evidently correlated with SOC, with the correlation coefficients of 0.919 and 0.952 in the surface and subsurface soil layers (P < 0.01), respectively. Particularly, increasing fulvic and humic acid-like compounds of WSOC promoted the bioavailability of nutrient elements, thereby increasing the crop yields. Therefore, biochar application is an effective means to fertilize middle-low yield soils through increasing SOC sequestration and nutrient reserves, or adjusting soil C:N value to a proper range, thereby reducing nutrient loss and increasing wheat yield., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Afforestation is an essential process of ecological restoration, landscape reconstruction, and environmental improvement. While large-scale plantations have restored the fragile ecosystems of the Qinghai-Tibet Plateau, they have also changed local soil characteristics. A 30-year-old typical planted forest on the eastern Qinghai-Tibet Plateau was selected to determine the long-term ecological effects of artificial forests on the soil in this study. Physicochemical soil characteristics at varying soil depths and relative soil parameters, such as element stoichiometry and growing stock, were quantified on the different plantations. This soil quality information was used to construct an MDS-SQI Model. Our findings revealed that soil TN, TK, TP, and AP content was higher than pre-afforestation baseline values, while SOC and pH values were lower. Amounts of soil nutrients SOC, TN, TP, TK, AP, and AK, were positively correlated in the artificial forests. The ratio of soil C/N was higher and ratios C/P and N/P were lower in poplar than the Chinese pine plantation. The soil quality index values calculated from the MDS model were 0.31 and 0.40 for poplar and Chinese pine plantations in the top 30 cm and 0.55 and 0.46 in the 100 cm depth, respectively, which indicated that the two plantations had low-quality soil. LiDAR satellite imagery was used to estimate a growing stock of 7723 m 3 and 435 m 3 in the poplar and Chinese pine plantations. The results suggest that the artificial forest improves soil properties overall but that different stand forests have discrete effects on the soil environment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A total of 63 soil samples were collected from three soil profiles (yellow soil, red loam, red soil) from Jiulongjiang river catchment to investigate the distribution, controlling factors, and toxic risks of heavy metals, including Cr, Mn, Fe, Cu, Zn, Cd, Pb, and Ni. The results showed that Cr and Cd in soils were enriched. The relationships between heavy metals and soil properties were assessed by principal component analysis. The results indicated that soil organic matter (SOM) played a fundamental role in controlling Cd and Pb in yellow soil and red loam sites. The Cd was significantly correlated with Pb and Cu, and Cr, Zn, Ni, Fe displayed strong correlations with each other, however, no statistical correlation was found between Cd and Cr. The enrichment factor and geoaccumulation index analyses showed that the soils in the study area were contaminated by Cd. Potential ecological risk analyses indicated that Cd posed a considerable ecological risk in yellow soils, and posed a moderate ecological risk in red loams and red soils., Competing Interests: The authors declare no conflict of interest.

The Bayan Obo Mine, the largest rare earth element (REE) deposit ever found in the world, has been mined for nearly 60 years for iron and rare earth elements. To assess the influences of mining activities on geochemical behavior of REEs in soils, 27 surface soil samples and three soil profile samples were collected from different directions in the vicinity of the mine area. The total concentrations of REEs in surface soils varied from 149.75 to 18,891.81 mg kg(-1) with an average value of 1906.12 mg kg(-1), which was apparently higher than the average values in China (181 mg kg(-1)). The order of the average concentrations of individual REEs in surface soils was similar to that in Bayan Obo ores, which confirmed that the concentration and distribution of REEs in the soils was influenced by the mining activities. The concentrations of single REE in the soil profiles showed a similar trend with depth with an increase at 0-25 cm section, then decreased and remained relatively stable in the deep part. The normalized curves inclined to the right side, showing the conspicuous fractionation between the light and heavy REEs, which supported by the North American Shale Composite (NASC) and Post-Archean Australian Shale (PAAS) normalized concentration ratios calculated for selected elements (La N /Yb N , La N /Sm N , Gd N /Yb N ). Slight positive Ce anomaly and negative Eu anomaly were also observed.

Rare earth mine tailing dumps are environmental hazards because tailing easily leaches and erodes by water and wind. To assess the influence of mine tailing on the geochemical behavior of rare earth elements (REEs) in soil, sixty-seven surface soil samples and three soil profile samples were collected from different locations near China's largest rare earth mine tailing. The total concentration of REEs in surface soils ranged from 156 to 5.65 × 10(4) mg·kg(-1) with an average value of 4.67 × 10(3) mg·kg(-1), which was significantly higher than the average value in China (181 mg·kg(-1)). We found obvious fractionation of both light and heavy REEs, which was supported by the North American Shale Composite (NASC) and the Post-Archean Average Australian Shale (PAAS) normalized concentration ratios calculated for selected elements (La(N)/Yb(N), La(N)/Sm(N) and Gd(N)/Yb(N)). A slightly positive Ce anomaly and a negative Eu anomaly were also found. For all 14 REEs in soils, enrichment was intensified by the mine tailing sources and influenced by the prevailing wind.

Introduction: Through leaching experiments and simulated rainfall experiments, characteristics of vertical leaching of exogenous rare earth elements (REEs) and phosphorus (P) and their losses with surface runoff during simulated rainfall in different types of soils (terra nera soil, cinnamon soil, red soil, loess soil, and purple soil) were investigated., Results and Analyses: Results of the leaching experiments showed that vertical transports of REEs and P were relatively low, with transport depths less than 6 cm. The vertical leaching rates of REEs and P in the different soils followed the order of purple soil > terra nera soil > red soil > cinnamon soil > loess soil. Results of the simulated rainfall experiments (83 mm h⁻¹) revealed that more than 92% of REEs and P transported with soil particles in runoff., Conclusion: The loss rates of REEs and P in surface runoff in the different soil types were in the order of loess soil > terra nera soil > cinnamon soil > red soil > purple soil. The total amounts of losses of REEs and P in runoff were significantly correlated.

A number of remediation measures have been used in paddy fields to alleviate serious cadmium (Cd) contamination, which may pose a public health risk through the food chain. In this study, a field trial was conducted in paddy fields with slight–moderate Cd contamination to investigate the remediation effects of combined remediation measures (CRMs), including the use of Cd-safe rice (Oryza sativa L.) cultivars, water management modes (WMMs), lime application (LA), soil amendment application (SAA), and foliar silicon (Si) fertilizers. Two groups of field trials were designed including CRMs with selenium (Se) and without selenium (non-Se) application. The results show that soil measures (LA + SAA) can increase the soil pH by 0.99 and decrease the soil DTPA-extracted Cd content by 34.19% (p < 0.05). All measures used in the present study significantly decreased the Cd content in husked rice and yield, except for the WMMs; the CRMs achieved the best results, and Se application enhanced the effects of all measures. This study shows that CRMs significantly decreased the Cd content in husked rice by 58.10%; this value increased to 72.69% after Se application (p < 0.05). These results provide useful information for selecting remediation measures in paddy fields with slight–moderate Cd contamination. [ABSTRACT FROM AUTHOR]

Abstract Due to increasing anthropogenic disturbance, various pollutants have been frequently detected in QingHai-Tibet Plateau, where the environment is extremely fragile and sensitive to human activities. In this study, 51 sampling sites with different land covers were selected in a sub-basin in the Huangshui watershed in eastern QingHai-Tibet Plateau. A total of 102 soil samples were collected at surface (0–20 cm) and subsurface (20–40 cm) depths for studying on heavy metal pollution in this region. The relationships between land cover types and spatial distribution of five heavy metals Cr, Cu, Cd, Pb, and Zn were systematically analyzed combing field survey, remote-sensing database, and geostatistical methods. The relationships between soil physiochemical properties and heavy metals were assessed by geostatistics, co-occurrence network analysis and geographically weighted regression (GWR) model. The results indicated that the average concentrations of all five heavy metals in soil were higher than the local background values, indicating the influence of anthropogenic inputs of these elements into environment. Strong positive correlations were observed between some heavy metals and soil physic-chemical properties in different land covers, combined with the geoaccumulation index, human activities contribution can be interpolated. The Cr and Zn in surface soils are explainers for Cr and Zn in subsurface soils in the GWR models respectively, as well as the area of different land cover. Cd contamination was specifically analyzed due to its degree of contamination and then the sources of Cd were identified such as energy production as well as chemical fertilizers. The results of this study can provide basic data for long-term accumulation of heavy metals in soils under different land uses in QingHai-Tibet Plateau. Graphical abstract Unlabelled Image Highlights • Correlation between heavy metals and land use was analyzed by polygon definition and raster correlation. • Geographically weighted regression was used to identify the relationships between heavy metals. • Contamination sources were identified using combination of land cover and geoaccumulation index. [ABSTRACT FROM AUTHOR]

Highlights: [•] Rare earth elements has influence on P adsorption process in soil. [•] P adsorption declined when soils were amended with lower concentration rare earth. [•] Langmuir equation fitted P adsorption in all five types soils. [•] P desorption increased when soil were amended with rare earth. [ABSTRACT FROM AUTHOR]

Abstract: Controlling phosphorous (P) inputs through management of its sources and transport is critical for limiting freshwater eutrophication. In this study, characteristics of exogenous rare earth elements (REEs) and P and their losses with surface runoff (both in the water and sediments) during simulated rainfall experiments (83mmh−1) were investigated. The results revealed that on average most REEs (La, 94%; Nd, 93%; Sm, 96%) and P (96%) transported with sediments in the runoff. The total amounts of losses of REEs and P in the runoff were significantly correlated, suggesting the possibility of using REEs to trace the fate of agricultural nonpoint P losses. [Copyright &y& Elsevier]

Based on systematic sampling of soil around the coal-fired power plant (CFPP), the content of Hg was determined, using atomic fluorescence spectrometry. The result shows that the content of Hg in soil is different horizontally and vertically, ranges from 0.137 to 2.105 mg/kg (the average value is 0.606 mg/kg) and is more than the average content of Hg in Shaanxi, Chinese and world soil. In this study, spatial distribution and hazard assessment of mercury in soils around a CFPP were investigated using statistics, geostatistics and geographic information system (GIS) techniques. Ordinary kriging was carried out to map the spatial patterns of mercury and disjunctive kriging was used to quantify the probability of the Hg concentration higher than the threshold. The maps show that the spatial variability of the Hg concentration in soils was apparent. These results of this study could provide valuable information for risk assessment of environmental Hg pollution and decision support. [ABSTRACT FROM AUTHOR]

Intensive anthropogenic activity has triggered serious heavy metal contamination of soil. Land use and land cover (LULC) changes bear significant impacts, either directly or indirectly, on the distribution of heavy metal in soils. A total of 180 samples were acquired from various land covers at different depths, namely surface soils (020 cm) and subsurface soils (20–40 cm). Spatial interpolation, geographically weighted regression (GWR) and self-organizing map (SOM) were used to discern how variations in the spatial distributions of soil heavy metals were caused by human activities for different land uses, and how these pollutants contributed to environmental risks. The medium concentrations of Cd, Cr, Cu, Pb and Zn in surface soil all exceeded the corresponding local background values in flat cropland and developed area soil. The overall ecological risk level of the study varied from low to medium. The GWR model indicated that the land use intensity had a certain influence on the accumulation of heavy metals in the surface soil. K-means clustering of the SOM revealed that the type of LULC also contributed to the redistribution of heavy metals in the surface soil. Image 1 • Heavy metal differentiation in soil was described by spatial interpolation. • The correlation between heavy metals and land use intensity was analyzed. • Most of samples from cropland and developed areas were polluted by heavy metals. • SOM was used to identify the impact of LULC on heavy metal accumulation in soil. Changes in land use and land cover caused by human activities affect the enrichment and redistribution of heavy metals in soil. [ABSTRACT FROM AUTHOR]

The accurate identification of sources for soil heavy metal(loid) is difficult, especially for multi-functional parks, which include multiple pollution sources. Aiming to identify the apportionment and location of heavy metal(loid)s pollution sources, this study established a method combining principal component analysis (PCA), Geodetector, and multiple linear regression of distance (MLRD) in soil and dust, taking a multi-functional industrial park in Anhui Province, China, as an example. PCA and Geodetector were used to determine the type and possible location of the source. Source apportionment of individual elements is achieved by MLRD. The detection results quantified the spatial explanatory power (0.21 ≤ q ≤ 0.51) of the potential source targets (e.g., river and mining area) for the PCA factors. A comparative analysis of the regression equation (Model 1 and Model 3) indicated that the river (0.50 ≤ R 2 ≤0.78), main road (0.47 ≤ R 2 ≤ 0.81), and mine (0.14 ≤ R 2 ≤ 0.92) (p < 0.01) were the main sources. Different from the traditional source apportionment methods, the current method could obtain the exact contributing sources, not just the type of source (e.g., industrial activities), which could be useful for pollution control in areas with multiple sources. [Display omitted] • PCA- Geodetector-MLRD was used to determine the location of the sources, not just the type of source. • The river, main road, mining area, metal plant, and community can significantly explain the PCA factors. • A distance-based prediction model for heavy metal concentration was established and its effectiveness was verified. [ABSTRACT FROM AUTHOR]

The production of 2,4,6-trinitrotoluene (TNT) produces a great deal of waste water, and dinitrotoluene sulfonates (DNTs) are the main pollutants in its waste. This paper presents a pilot investigation on the geochemical transformation of DNTs affected by historical wastewater spillage from a typical TNT production company in Northwest China. In the horizontal direction, DNTs diffused from the evaporation pond to the surrounding area of the site, and the concentration of DNTs in the evaporation pond surface soil exceeded 1000 mg/kg. The horizontal distribution of DNTs in the site showed a migration trend to the east and south of evaporation, which was consistent with the terrain of high northwest and low southeast of the site. Due to the high water solubility of pollutants, water flow is the main driving force for the horizontal distribution of DNTs. In the vertical direction, the concentration of pollutants gradually increased with the depth of the soil. DNTs are mainly adsorbed in the third layer (6.0–8.0 m). It can be seen that the accumulation of the 2,4-DNTs-3-SO 3 - is obviously larger than that of the 2,4-DNTs-5-SO 3 -, which may be related to the steric hindrance effect of sulfonic acid groups in the two isomers. Results showed DNTs distribution strongly linked to soil physicochemical properties and the migration of DNTs in soil exhibited obvious heterogeneity in time and space. The carcinogenic risks in surface soil (0–1.5 m) and lower soil (1.5–6.0 m, 6.0–8.0 m) are all higher than 1✕10−6; non-carcinogenic risk surface soil (0–1.5 m) is 4.011✕10, which is greater than 1, indicating that they may cause certain harm to the human body. Meanwhile, this study presented a pioneering investigation for the contamination and geochemical transfer of DNTs. [Display omitted] • Geochemical fate of sodium dinitrotoluene sulfonate (DNTs) in soil was studied. • The spatial variability of DNTs and soil properties interrelated. • Exposure risk assessment of DNTs pollution is calculated. • Recommendations in both management and policy implication are proposed. [ABSTRACT FROM AUTHOR]