Search Results (97)

To elucidate the long-term spatiotemporal patterns and key drivers factors, this study employed a meta-analysis of data from soil containing Potentially Toxic Elements (Cd, As, Cr, Hg, and Pb) in Chinese farmland soils from 2003 to 2025. The geoaccumulation index, the potential ecological risk index, and standard deviation ellipses were used to assess the spatiotemporal evolution of heavy metal accumulation and ecological risk, while the Random forest–SHapley Additive exPlanations (RF-SHAP) method was employed to identify driving mechanisms. At the national scale, Cd and Hg are significantly enriched relative to the background values, whereas As, Cr, and Pb remained at relatively low levels, with enrichment ranked as Cd > Hg > Pb > Cr > As. Cd and Hg indicated mild pollution, but the Sichuan Basin emerged as a hotspot, where Cd reached moderate pollution and showed strong ecological risk, and Hg also exhibited high ecological risk. Over the past two decades, the contamination center shifted from coastal to southwestern inland regions, with an expanded and more dispersed distribution. Since 2017, Cd and Hg pollution levels have stabilized, suggesting that the aggravating trend has been preliminarily curbed. Industrial waste and wastewater discharge, irrigation and fertilization were identified as the primary anthropogenic factors of soil heavy metal accumulation, while climatic factors (temperature, precipitation, and solar radiation) and soil physicochemical properties (pH, clay content, and organic matter) played fundamental roles in spatial distribution and accumulation. Our findings call for targeted predictive research and policies to manage heavy metal risks and preserve farmland sustainability in a changing climate. Full article

In order to investigate the current status of soil heavy metal pollution, ecological risk, and risk sources in the black soil area of the Eastern Inner Mongolia Province, topsoil (0–20 cm) samples from farmland in the black soil area (N = 163) were collected to determine the contents of seven heavy metals. The levels of soil heavy metal pollution and ecological risk in the study area were evaluated by combining the geo-accumulation index, potential ecological risk index, and static environmental carrying capacity; the positive matrix factorization (PMF) model was used to identify the pollution sources and contributions of heavy metals in the soil and analyze the risk levels to adults and children. The soil was predominantly weakly acidic, with mean values of Cr, Ni, Cu, As, Cd, Pb, and Zn of 61.77, 26.77, 17.07, 12.11, 0.08, 12.61, and 85.71 mg·kg⁻¹. The mean concentrations of heavy metals exceeded the background values, except for Pb, the mean concentration of which was lower than the soil background. Ni concentrations of 6.21% at the sampling sites exceeded the risk screening value for agricultural soils. The geo-accumulation index showed that Cr (55.15%) and As (54.00%) were mainly mild pollutants; the static environmental carrying capacity indicated that the soils were slightly polluted by Ni, As, and Zn; and the potential ecological risk indices of Cd, Ni, and As were at moderate levels. The PMF model analyzed three pollution sources: mixed agricultural practice–transportation sources (39.46%), mineral-related activity sources (27.01%), and pesticide–fertilizer agricultural practices (33.53%). The human health risk assessment indicated that 46.58% of sampling sites posed a carcinogenic risk to children, with Ni as the main carcinogenic element. In conclusion, the potential contamination of As, Cd, Ni, Cr, and Zn in the Eastern Inner Mongolia farmland black soil area should be further studied. Full article

With the escalating application of chemical fertilizers, the potential for environmental pollution has increased significantly. Currently, the degradation of soil quality due to the indiscriminate use of chemical fertilizers poses a more pressing challenge than ever before, threatening both human food production and the environment. The utilization of organic amendments not only enables the efficient recycling of organic waste resources but also reduces the reliance on chemical fertilizers. Meanwhile, organic amendments play a crucial role in soil improvement, helping to stabilize and enhance crop yields. Numerous studies have investigated the impacts of organic amendments on various aspects of crop production, including soil biology, biochemistry, heavy metal accumulation, and greenhouse gas (GHG) emissions. However, these studies have predominantly focused on isolated aspects rather than adopting a comprehensive perspective. Therefore, a comprehensive analysis of the positive and adverse effects of organic amendments is important in optimizing fertilizer use to meet crop nutrient demands and advancing carbon-neutral agriculture. This study mainly explores the intrinsic mechanism of the influence of organic amendments on soil physicochemical properties, enzyme activity and microbial diversity, heavy metal contamination and mobility, and GHG emissions in farmland. Finally, recommendations for the future development of organic amendments are proposed for promoting green and sustainable agricultural practices. Full article

This research investigated the characteristics and risks associated with heavy metal contamination in farmland soils surrounding an industrial aggregation area in Yuncheng City, southern Shanxi Province. It analyzed the concentrations and spatial accumulation patterns of eight heavy metal elements, employed principal component analysis (PCA) to identify sources, and assessed both the ecological and health risks. The results revealed the following: (1) The mean concentrations of Pb, Cd, As, Hg, Cr, Zn, Cu, and Ni in the study area were 26.1, 0.29, 13.4, 0.05, 61.4, 72.94, 27.15, and 32.33 mg·kg⁻¹, respectively. These concentrations were elevated above local background levels but remained within Chinese regulatory thresholds for agricultural soil. According to the geoaccumulation index, only Cd was classified as slightly polluted, while the other elements were essentially uncontaminated. The Nemerow comprehensive pollution index indicated light pollution. The potential ecological risk index identified Cd and Hg as the primary contributors to ecological risk, indicating moderate contamination. (2) Source apportionment results revealed that As, Cr, and Ni originated from industrial–natural sources; Cd, Zn, and Cu were linked to industrial production; and Pb and Hg were attributed to mining and traffic sources. (3) Health risk assessments suggested that non-carcinogenic risks for adults and children (0.28 and 0.51, respectively) were within safe limits. However, the carcinogenic risk for children (1.02 × 10⁻⁴) exceeded the acceptable threshold, while the level for adults (4.67 × 10⁻⁵) remained acceptable. This study provides a scientific basis for preventing, controlling and remediating local heavy metal contamination in soil. Full article

Soils in alpine mining areas suffer from severe heavy metal contamination and infertility, yet little is known about the effects of different materials on soil improvement in such regions. In this study, a field experiment was conducted in farmlands contaminated by the Lanping lead–zinc mine in Yunnan, China, to compare the effects of four materials (biochar, organic fertilizer, lime, and sepiolite) on soil properties, heavy metal (lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) fractions and their availability, and the growth of Phaseolus coccineus L. Results showed that biochar and organic fertilizer significantly enhanced soil nutrient content and enzyme activities. Lime, biochar, and sepiolite effectively reduced heavy metal bioavailability by promoting their transition to residual fractions. Notably, biochar outperformed other materials by substantially increasing grain yield (by 82%), improving nutritional quality (sugars, protein, and starch contents raised by 20–88%), and reducing heavy metal accumulation in grains (by 36–50%). A comprehensive evaluation based on subordinate function values confirmed biochar as the most effective amendment. Structural equation modeling further revealed that biochar promoted plant growth and grain quality primarily by enhancing soil available nutrients and immobilizing heavy metals. These findings demonstrate the strong potential of biochar for remediating heavy metal-contaminated farmlands in alpine lead–zinc mining regions. Full article

Heavy metals in farmland soils pose severe threats to agricultural productivity and food safety. To investigate contamination in the soil–wheat/corn system, 24 sets of adjacent farmland soil, wheat, and corn plant samples were collected near metal smelting facilities in Jinchang City, a typical urban oasis in northwestern China. Concentrations of Ni (nickel), Cu (copper), and Co (cobalt) were measured. Results indicated mean soil concentrations of 143.66 mg kg⁻¹ (Ni), 130.00 mg kg⁻¹ (Cu), and 24.04 mg kg⁻¹ (Co), all exceeding background values for Gansu Province, confirming that the sampling sites exhibit varying degrees of contamination with Ni, Cu, and Co. Correlation analyses revealed strong intermetal relationships (Ni, Cu, Co; p < 0.01), while spatial distribution patterns showed that Ni in wheat and corn grains closely mirrored soil Ni distribution. The bio-concentration factor (BCF) for wheat roots surpassed that of corn roots, highlighting wheat’s greater susceptibility to heavy metal uptake. Heavy metal levels in crop organs exceeded limits set by the Safety Guidelines for Feed Additives. Geo-accumulation indices and potential ecological risk assessments demonstrated substantial metal accumulation and varying ecological risks, with contamination levels ranked as Cu > Ni > Co. Non-carcinogenic hazard indices indicated elevated health risks for children consuming locally grown wheat and corn. This study provides a scientific foundation for crop rotation strategies and soil remediation in the region. Full article

This study evaluates the pollution status, ecological risks, health risks, and sources of heavy metals from farmland in a mining city located in the Yangtze River basin, East China. A total of 2361 samples of topsoil were collected and analyzed for the concentration of five heavy metals and pH. The Nemerow index was used to assess integrated pollution, while absolute principal component scores-multiple linear regression (APCS-MLR) was used to identify the sources of heavy metals. The results revealed that, excluding Hg and Cr, the concentrations of Cd, As, and Pb in some samples exceeded intervention values, with Cd concentrations in 19.7% of samples surpassing this threshold. Based on the Nemerow index, 68.8% of sites were contaminated, with 27.4% classified as heavily polluted, indicating significant pollution in this area. Cd posed the primary ecological risk, with 19.8% of sites at high risk or above, also presenting carcinogenic risks to adults. Additionally, As exceeded safety thresholds for hazard quotient (HQ = 1) and carcinogenic risk (CR = 1 × 10⁻⁴). APCS-MLR revealed that heavy metals in farmland were mainly influenced by mining, agricultural activities, and natural soil-forming processes. This study offers insights into farmland heavy metal management and highlights industrial pollution sources in mining areas. Full article

To explore strategies for the safe utilization of farmland co-contaminated with cadmium (Cd) and lead (Pb), this field study systematically evaluated the impacts of humic acid (HA) and potassium fulvate (PF) at different application rates (0, 1500, 3000, and 4500 kg·ha⁻¹) on the growth, yield, and translocation of Cd and Pb within the soil–plant system of maize (Zea mays L.). The results showed that while HA and PF did not significantly alter total soil Cd and Pb concentrations, they markedly reduced their bioavailable fractions. This mitigation of heavy metal phytotoxicity significantly promoted maize growth and yield, with the high-dose HA treatment increasing yield by a maximum of 32.9%. Both amendments dose-dependently decreased Cd and Pb concentrations, bioconcentration factors (BCF), and translocation factors (TF) in all maize tissues, particularly in the grains. At equivalent application rates, PF was slightly more effective than HA in reducing heavy metal concentrations in the grains. Notably, a significant positive correlation was observed between Cd and Pb concentrations across all plant parts, confirming a synergistic accumulation and translocation mechanism. This synergy provides a physiological explanation for the broad-spectrum immobilization efficacy of these humic substances. In conclusion, applying HA and PF presents a dual-benefit strategy for increasing yield and reducing risks in Cd- and Pb-contaminated farmlands. This study proposes a differentiated application approach: PF is the preferred option when ensuring food-grade safety is the primary goal, whereas high-dose HA is more advantageous for maximizing yield in soils with low-to-moderate contamination risk. Full article

Selenium (Se) is a natural detoxifier of the heavy metal mercury (Hg), and the interaction between Se and Hg has been widely investigated. However, the ecological response of Hg to Se in Hg-contaminated farmland requires further study, especially the relationship between Se–Hg interactions and soil abiotic and biological properties. Through a field experiment, the effects of different levels of exogenous Se (0, 0.50, 0.75, 1.00, and 2.00 mg kg⁻¹) on Hg and Se transport in maize, soil properties, enzyme activities, and the microbial community in Hg-contaminated farmland were systematically studied. The Se treatments significantly reduced the Hg concentration in maize roots, stems, leaves, and grains and significantly increased the Se concentration in maize tissues. Except for the 0.75 mg kg⁻¹ Se treatment which significantly increased electrical conductivity compared to the control, other Se treatments had non-significant effect on soil physicochemical properties (pH, conductivity, organic matter content, and cation exchange capacity) and oxidoreductase activities (catalase, peroxidase, and ascorbate peroxide). The activities of soil invertase, urease, and alkaline phosphatase increased significantly after Se application, and the highest enzyme activities were observed with a 0.50 mg kg⁻¹ Se treatment. The bacteria and fungi with the highest relative abundance in this study were Proteobacteria (>30.5%) and Ascomycota (>73.4%). The results of a redundancy analysis and predictions of the microbial community showed that there was a significant correlation between the soil nutrient cycle enzyme activity, microbial community composition, and microbial community function. Overall, exogenous Se application was found to be a viable strategy for mitigating the impact of Hg stress on ecosystems. Furthermore, the results provide new insights into the potential for the large-scale application of Se in the remediation of Hg-contaminated farmland. Full article

Soil heavy metal pollution threatens agricultural safety and human health, with Cd exceeding standards being the most common problem in contaminated farmland. The development of hyperspectral remote sensing technology has provided a novel methodology of quickly and non-destructively monitoring heavy metal contamination in soil. This study aims to explore the potential of an interpretable Stacking ensemble learning model for the estimation of soil Cd contamination in farmland hyperspectral data. We assume that this method can improve the modeling accuracy. We chose Zhangjiagang City, Jiangsu Province, China, as the study area. We gathered soil samples from wheat fields and analyzed soil spectral data and Cd level in the lab. First, we pre-processed the spectra utilizing fractional-order derivative (FOD) and standard normal variate (SNV) transforms to highlight the spectral features. Second, we applied the competitive adaptive reweighted sampling (CARS) feature selection algorithm to identify the significant wavelengths correlated with soil Cd content. Then, we constructed and compared the estimation accuracy of multiple machine learning models and a Stacking ensemble learning method and utilized the Optuna method for hyperparameter optimization. Ultimately, the SHAP method was used to shed light on the model’s decision-making process. The results show that (1) FOD can further highlight the spectral features, thereby strengthening the correlation between soil Cd content and wavelength; (2) the CARS algorithm extracted 3.4–6.8% of the feature wavelengths from the full spectrum, and most of them were the wavelengths with high correlation with soil Cd; (3) the optimal estimation precision was achieved using the FOD1.5-SNV spectral pre-processing combined with the Stacking model (R² = 0.77, RMSE = 0.05 mg/kg, RPD = 2.07), and the model effectively quantitatively estimated soil Cd contamination; and (4) SHAP further revealed the contribution of each base model and characteristic wavelengths in the Stacking modeling process. This research confirms the advantages of the interpretable Stacking model in hyperspectral estimation of Cd contamination in farmland wheat soil. Furthermore, it offers a foundational reference for the future implementation of quantitative and non-destructive regional monitoring of heavy metal contamination in farmland soil. Full article

Systematic assessment of heavy metal contamination in agricultural soils is critical for addressing ecological and public health risks in industrial-intensive cities like Lanzhou, with direct implications for achieving UN Sustainable Development Goals (SDGs) 2 (Zero Hunger), 15 (Life on Land), and 3 (Good Health). The present study evaluates farmland soils around six industrial sectors: waste disposal (WDZ), pharmaceutical manufacturing (PMZ), chemical manufacturing (CMZ), petrochemical industry (PIZ), metal smelting (MSZ), mining (MZ) and one sewage-irrigated zone (SIZ) using geo-accumulation index, Nemerow composite pollution index, potential ecological risk index, and health risk models. The following are the major findings: (1) SIZ and PMZ emerged as primary contamination clusters, with Hg (I_geo = 1.89) and Cd (I_geo = 0.61) showing marked accumulation. Chronic wastewater irrigation caused severe Hg contamination (0.97 mg·kg⁻¹) in SIZ, where 100% of the samples reached strong polluted levels according to the Nemerow composite pollution index; (2) Hg and Cd dominated the ecological risks, with 41.32% of the samples exhibiting critical Hg risks (100% in PMZ and SIZ) and 32.63% showing strong Cd risks; and (3) oral ingestion constituted the dominant exposure pathway. Children faced carcinogenic risks (CR = 1.33 × 10⁻⁴) exceeding safety thresholds, while adult risks remained acceptable. Notably, high Hg and Cd levels did not translate to proportionally higher health risks due to differential toxicological parameters. The study recommends prioritizing Hg and Cd control in PMZ and SIZ, with targeted exposure prevention measures for children. Full article

Heavy metal pollution severely affects soil and rice quality in China. In a one-year field experiment conducted in Hg-Cd co-contaminated farmland in Tongren, Guizhou, we examined the effects of low-accumulation rice cultivars, soil amendments (Fupei (D1), Wansan (D2), Shengwujun (D3), and Shigou (D4)) and foliar barrier agents on Hg and Cd transport and uptake. The rice cultivar Longliangyouhuanglizhan (P1) showed lower Hg and Cd accumulation. When combined with amendments, P1 further reduced health risks. All amendments effectively reduced non-carcinogenic health risks, with Fupei reducing Hg and Cd accumulation in rice by 65.16% and 97.54%, respectively, achieving a 91.74% reduction in health risks. Foliar barrier agents further decreased heavy metal content in rice. Additionally, D1 was the most cost-effective option. Soil assessments showed amendments reduced available Hg content by 66.67–70.51%, while Cd content increased by 3.51–16.67%. Mechanistic analysis indicated that D1 and D2 mainly immobilized heavy metals through adsorption and precipitation, while D3 facilitated removal via microbial reduction, and D4 relied on adsorption. Overall, D1 was most effective in mitigating heavy metal risks and improving soil quality, providing a comprehensive strategy for managing contamination in rice production with important implications for food safety and sustainable agriculture. Full article

Rapid socio-economic transition is often accompanied by intensive anthropogenic activities, leading to a significant build-up of heavy metals within farmland soils. However, this unwanted outcome may not be fully uniform but exhibit spatial variability, particularly involving different land uses. Based on 1839 topsoil samples from China’s Sunan Economic Region, this study estimated the contamination profiles and associated ecological risks posed by five heavy metals (As, Cd, Cr, Pb, and Hg) across cash-crop and cereal-crop soils. Further, we applied a combination of geostatistics and positive matrix factorization (PMF) model to identify the targeted zones, priority pollutants, and their underlying sources to pave the way for formulating detailed and fine-scale risk-mitigation strategies. Our results revealed that heavy metal pollution in Sunan displayed significant spatial variability, predominantly influenced by localized Hg and Cd accumulation, with more severe contamination observed in cash-crop soils compared to cereal-crop soils. The 232,532 ha of agricultural land could be designated as the targeted zones in which excessive Hg and Cd accumulation can be identified as the priority pollutants contributing to potential ecological risk. PMF modeling also suggested that within targeted zones, Cd accumulation was predominantly driven by intensive agrochemical application, whereas multiple sources simultaneously determined Hg accumulation. Our findings offer valuable guidance for optimizing land management strategies aimed at mitigating agricultural soil degradation driven by intensive anthropogenic activities. In addition, the integrated approach highlighted the crucial values in aspects to spatially identify risk-targeted zones and priority pollutants. Full article

Heavy metal pollution refers to the presence of excessive levels of heavy metal elements in soil beyond their natural background concentrations, posing serious threats to human health and ecological systems. Several factors are involved in the contamination disparity in agriculture soils from various terrains, demanding extra care. An examination of the topographical HM dispersions in farmland soils from the Licheng District was conducted to reveal spatial changes in pollution levels and sources and to establish an empirical framework to develop targeted remediation strategies and promote sustainable land management practices. Cd and As had over-standard rates of more than 50% in the low-lying area, whereas the HMs in the high-lying area had over-standard rates of more than 50%. Also, the rates of HMs in high terrain were higher than in low terrain. Using the single-factor pollution index, only low-lying Cu, Ni, Pb, and Hg contamination levels were clean in low-lying and high-lying areas. The overall decline in HM pollution occurred from high to low terrain, triggered by soil physicochemical properties and human interventions. Meanwhile, strong anthropogenic influence fell in high terrain for pollution. Nevertheless, low levels of HM-integrated contamination prevailed in both topographies. Natural and anthropogenic processes gave rise to environmental pollution, such as soil formation, fertilization, metal smelting, and traffic emissions. Overall, the district held a low risk for HMs. The results highlight that strong anthropogenic interventions resulted in increased HM contamination, in addition to natural processes. It is possible to further reduce HM pollution and risk by promoting scientific agricultural techniques, new energy vehicles, and cleaner production. Full article

The accumulation of heavy metal cadmium (Cd) in farmland soil in edible parts of crops seriously threatens plant growth, human health, and even the global ecological environment. Finding stabilization remediation technology is an important means to treat Cd-contaminated soil. This study comprehensively evaluated the synergistic effects of independent or combined application of biochar (BC) (10, 30 g kg⁻¹) and nano zero-valent iron (nZVI) (0.1% w/w) on soil properties and morphological and physiological traits of pakchoi (Brassica rapa L. subsp. chinensis) under Cd (1, 3 mg kg⁻¹) stress by pot experiments. It was shown that Cd toxicity negatively affected soil properties, reduced pakchoi biomass and total chlorophyll content, and increased oxidative stress levels. On the contrary, the combined application of BC (30 g kg⁻¹) and nZVI (0.1%, w/w) reduced the Cd accumulation in the shoot parts of pakchoi from 0.78 mg·kg⁻¹ to 0.11 mg·kg⁻¹, which was lower than the Cd limit standard of leafy vegetables (0.20 mg kg⁻¹) in GB 2762-2017 “National Food Safety Standard”. Compared with the control, the treatment group achieved a 61.66% increase in biomass and a 105.56% increase in total chlorophyll content. At the same time, the activities of catalase (CAT) and superoxide dismutase (SOD) increased by 34.86% and 44.57%, respectively, and the content of malondialdehyde (MDA) decreased by 71.27%. In addition, the application of BC alone (30 g·kg⁻¹) increased the soil pH value by 0.43 units and the organic carbon (SOC) content by 37.82%. Overall, the synergistic effect of BC (30 g kg⁻¹) and nZVI (0.1% w/w) helped to restore soil homeostasis and inhibit the biotoxicity of Cd, which provided a new option for soil heavy metal remediation and crop toxicity mitigation. Full article