Contamination Of Agricultural Soils Research Articles

Assessing heavy metal contamination in agricultural soils: a new GIS-based Probabilistic Pollution Index (PPI) – case study: Guarda Region, Portugal

ABSTRACT Soil contamination by heavy metals is a global agricultural problem, as these elements can be absorbed by plants and transferred to humans through the food pathway. Current contamination assessment methods rely on in situ sample collection, which restricts the evaluation process due to the number of samples that can be analysed and the associated costs. This study addresses the need for a more efficient and cost-effective approach to identifying areas at risk of heavy metal contamination without the logistical constraints of physical sampling. To meet this challenge, we developed a new Probabilistic Pollution Index (PPI), calculated by integrating GIS tools with an 8-parameter probability-risk matrix to identify agricultural areas potentially contaminated by heavy metals. The factors considered included roads, industrial sites, pH levels, soil organic matter content, terrain slope, soil texture, mining areas, and drainage. Each parameter was classified and reclassified to produce a contamination risk map, categorizing each pixel into five levels of risk. To test the PPI, data analysis, parameter classification, and reclassification were applied in the district of Guarda, Portugal. The PPI map revealed that the central portion of the Guarda municipality, along with specific zones in Celorico da Beira, Sabugal, Mêda, and Pinhel, exhibited a high-probability risk of contamination. Given the agricultural expanse within each municipality, enhanced monitoring of heavy metal levels was recommended for Mêda, Pinhel, and Vila Nova de Foz Côa. This index provides a scalable, cost-effective, and easily replicable tool for identifying potential contamination hotspots and the sources and processes of contamination. Designed as a first-line method for large-scale assessments, it supports governmental decision-making and facilitates targeted risk mitigation strategies through a low-cost approach.

Use of Hydroxyapatite Nanoparticles to Reduce Cd Contamination in Agricultural Soils: Effects on Growth and Development of Chenopodium quinoa Willd

Use of Hydroxyapatite Nanoparticles to Reduce Cd Contamination in Agricultural Soils: Effects on Growth and Development of Chenopodium quinoa Willd

Identification of driving factors for heavy metals and polycyclic aromatic hydrocarbons pollution in agricultural soils using interpretable machine learning.

This study integrated data-driven interpretable machine learning (ML) with statistical methods, complemented by knowledge-driven discrimination diagrams, to identify the primary driving factors of heavy metal (HM) and polycyclic aromatic hydrocarbon (PAH) contamination in agricultural soils influenced by complex sources in a rapidly industrializing region of a megacity in southern China. First, the statistical characteristics of the concentrations of HMs and PAHs, and their correlations with the environmental covariates were explored. Three ML models and a statistical model comprising multiple environmental variable predictors were developed and assessed to predict the concentration of HMs in the agricultural soil. The Shapley Additive Explanations (SHAP) tool was introduced to reveal the influences of the main driving factors on pollutant concentrations. In addition, knowledge-based discrimination diagrams were adopted to discriminate the potential sources of the PAHs. Our findings indicated that Cd, Hg and Cu could be effectively predicted by the LightGBM and RF models. The identification of pollution drivers revealed that traffic emission, industry activity and irrigation significantly contributed to the pollution of Cd, Hg, Cu and high-ring PAHs in the study area, while the soil nature properties including SOM and pH also played crucial roles in influencing the HM and PAH concentrations. This work introduced an innovative approach to leverage ML for understanding complex urban soil pollution, thereby setting a precedent for data-driven environmental protection strategies to mitigate the pollution of HMs and PAHs. Future research is encouraged to optimize the models, enhance the prediction accuracy, and incorporate a broader range of influential parameters.

Assessment of Health Risks from Agricultural Soils Contaminated with Polycyclic Aromatic Hydrocarbons (PAHs) Across Different Land-Use Categories of Bangladesh

Polycyclic aromatic hydrocarbons (PAHs) are a matter of deep concern as they pose significant environmental and health hazards due to their persistence, bioaccumulation, and toxic effects. In soils, PAHs accumulate, contaminating ecosystems, entering food chains, and posing threats to plant and human health. This study conducted a comprehensive assessment of PAH contamination in agricultural soils (particle size < 20 µm) across various land-use categories and depths to determine contamination levels and associated health risks, as such comprehensive studies are very rare in Bangladesh. Soil samples were investigated using gas chromatography–mass spectrometry (GC–MS). The findings revealed that the concentrations of ∑16PAH ranged from 299 to 1928 µg/kg, with the lowest levels observed in research areas and the highest in industrial soils. Concentration trends were as follows: industrial areas > coastal areas > local market areas > rural areas > research areas. Higher concentrations were noted for individual PAHs such as Nap, Phe, BbF, and BkF (313.14 µg/kg ± 62.01 to 546.97 µg/kg ± 146.76), while the lowest concentrations were recorded for BghiP, DBahA, and Ind (1.25 µg/kg ± 1.10 to 5.74 µg/kg ± 3.77). PAH levels were highest in surface soils, following a depth sequence of 0–5 cm > 5–10 cm > 10–15cm. The results also showed that low-, intermediate-, and high-molecular-weight PAHs comprised 46.06–83.18%, 16.47–48.68%, and 0.23–6.51% of total PAHs, respectively. The source of PAHs was identified as integration of pyrogenic petrogenic. Children were found to have higher exposure through ingestion compared to adults, with lower exposure through inhalation and dermal pathways. The total incremental lifetime cancer risk (ILCR) for children ranged from 2.03 × 10−8 to 9.07 × 10−7, and for adults from 1.96 × 10−8 to 8.04 × 10−7. Both groups exhibited no carcinogenic risk, as per the USEPA threshold. These findings underscore the need for ongoing monitoring and management strategies to mitigate PAH contamination in agricultural soils, thus protecting environmental and public health concerns.

Trends in Heavy Metal Pollution in Agricultural Land Soils of Tropical Islands in China (2000-2024): A Case Study on Hainan Island.

Heavy metal contamination in agricultural soils has garnered increasing attention, yet research on the spatiotemporal trends of heavy metal pollution in tropical regions with multiple annual crop harvests remains limited. This study examines data from 41 studies published between 2000 and 2024, including 206 records from 4122 sampling points on Hainan Island in China, to investigate the spatial distribution and temporal trends of heavy metal pollution. The results reveal that the average concentrations of Cd, Pb, As, Cr, and Hg in surface soil samples from agricultural lands on Hainan Island are 0.12, 28.28, 4.36, 63.98, and 0.075 mg/kg, respectively, all below the risk screening thresholds set by the Soil Pollution Risk Control Standard for Agricultural Land (GB 15618-2018). Spatially, heavy metal concentrations exhibit considerable regional variation. Cd levels are lower in the central region but higher in the northern and southern parts of the island. Both the cumulative pollution index and potential ecological risk index are elevated at the northern and southern ends, indicating more severe pollution in these areas. Pb and As show similar spatial patterns, with higher concentrations in the west and lower concentrations in the east. Conversely, Cr has higher concentrations in the northeast and lower concentrations in the southwest. Hg levels are elevated at the northern and southern ends of the island, though the overall pollution and ecological risk in these areas remain relatively low. Temporally, the concentration of heavy metals in agricultural soils has increased overall over the past two decades, with peak values occurring between 2017 and 2023. From 2002 to 2013, the variation was modest, while the largest fluctuations occurred between 2014 and 2016. Among the metals, Cr exhibited the most significant increase, indicating the most severe pollution, followed by Cd and Hg. As and Pb showed relatively lower levels of contamination. Regarding exceedance rates, the exceedances were evaluated against the thresholds established in GB15618-2018 and GB15618-1995. Cd's exceedance rate increased from approximately 1% between 2002 and 2014 to between 7.78% and 20.93% in the following years, peaking in 2017. The exceedance rate for As rose slightly from 0% to 0.83%, with sporadic exceedances starting in 2015. Although these were relatively minor, a severe pollution point for As was observed in 2019. Exceedance rates for Pb and Cr increased significantly, from 0.75% and 7.50% in 2019 to 1.94% and 9.44% in 2023, reflecting increases of 4.8 to 10 times. These findings underscore the need for strengthened monitoring and management of heavy metal pollution in agricultural soils on Hainan Island to safeguard land quality and ensure the sustainability of local agricultural practices.

Nanoscale particles-induced mitigation of tannery wastewater chromium stress in rice: Implications for plant performance and human health risk assessment.

Due to the rapid increase in industrial and urban areas, environmental pollution is increasing worldwide, which is causing unwanted changes in air, water, and soil at biological, physical, as well as chemical levels that ultimately causing the negative effects in living things because of toxic level of chromium (Cr). However, nanotechnology is capturing great interest worldwide due to their stirring applications in various fields. For this purpose, a pot experiment was conducted to examine plant growth and exo-physiology in rice (Oryza sativa L.) under the different levels of wastewater 50% and 100% concentrations which were also primed with three nanoparticles (NPs)-copper oxide (nCuO), silicon (nSi), and zinc oxide (nZnO). The research outcomes indicated that elevated levels of wastewater in the soil (100%) notably reduced plant growth and biomass, photosynthetic pigments, and gas exchange attributes. However, increasing levels of Cr stress also induced oxidative stress in the plants by increasing malondialdehyde (MDA), hydrogen peroxide (H2O2), which also induced increased compounds of various enzymatic and non-enzymatic antioxidants and also the gene expression and sugar content. Furthermore, a significant increase in proline metabolism, the AsA-GSH cycle, and the pigmentation of cellular components was observed. Although, the application of nCuO, nSi, nZnO-NPs showed a significant increase in plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds, and their gene expression and also decreased oxidative stress. In addition, the application of nCuO, nSi, nZnO-NPs enhanced cellular fractionation and decreased the proline metabolism and AsA-GSH cycle in O. sativa plants. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

Does Microplastic Contamination in Agricultural Soils Decrease the Efficiency of Herbicides for Weed Control?

The contamination of agricultural soils by microplastics (MPs) has significant implications for herbicide efficacy and soil health. This study investigates the effects of MPs on critical processes such as the sorption, desorption, and degradation of herbicides, highlighting their influence on these compounds’ mobility, persistence, and bioavailability. MPs interact with herbicides through sorption mechanisms, often reducing the availability of these compounds for weed control by retaining them on their surfaces. This sorption not only limits the immediate efficacy of herbicides but also alters their desorption process, resulting in a prolonged release into the soil environment. Additionally, MPs can inhibit microbial activity involved in herbicide degradation, increasing the time degradation of the half-life of these substances and extending their persistence in the environment. These processes collectively enhance the risks of bioaccumulation and environmental contamination. Understanding these interactions is essential for developing strategies to mitigate the impacts of MPs on herbicide performance and promote sustainable agricultural practices.

PFAS, PCBs, PCDD/Fs, PAHs and extractable organic fluorine in bio-based fertilizers, amended soils and plants: Exposure assessment and temporal trends

Bio-based fertilizers (BBFs) produced from organic waste contribute to closed-loop nutrient cycles and circular agriculture. However, persistent organic contaminants, such as per- and poly-fluoroalkyl substances (PFAS), polychlorobiphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as well as polyaromatic hydrocarbons (PAHs) can be present in organic waste or be formed during valorization processes. Consequently, these hazardous substances may be introduced into agricultural soils and the food chain via BBFs. This study assessed the exposure of 84 target substances and extractable organic fluorine (EOF) in 19 BBFs produced from different types of waste, including agricultural and food industrial waste, sewage sludge, and biowaste, and through various types of valorization methods, including hygienization at low temperatures (<150 °C) as well as pyrolysis and incineration at elevated temperatures (150–900 °C). The concentrations in BBFs (ΣPFOS & PFOA: <30 μg kg−1, Σ6PCBs: <15 μg kg−1, Σ11PAHs: <3 mg kg−1, Σ17PCDD/Fs: <4 ng TEQ kg−1) were found to be below the strictest thresholds used in individual EU countries, with only one exception (pyrolyzed sewage sludge, Σ11PAHs: 5.9 mg kg−1). Five BBFs produced from sewage sludge or chicken manure contained high concentrations of EOF (>140 μg kg−1), so monitoring of more PFAS is recommended. The calculated expected concentrations in soils after one BBF application (e.g. PFOS: <0.05 μg kg−1) fell below background contamination levels (PFOS: 2.7 μg kg−1) elsewhere in the literature. This was confirmed by the analysis of BBF-amended soils from field experiments (Finland and Austria). Studies on target legacy contaminants in sewage sludge were reviewed, indicating a general decreasing trend in concentration with an apparent half-life ranging from 4 (PFOS) to 9 (PCDD/Fs) years. Modelled cumulative concentrations of the target contaminants in agricultural soils indicated low long-term risks. Concentrations estimated and analyzed in edible plant part were low, indicating that exposure by plant consumption is well below tolerable daily intakes.

Inoculation with multifunctional Bacillus sp. NEAU-DCB1-2 mitigates chromium toxicity in pakchoi (Brassica rapa ssp. chinensis) through a multi-level mechanism

Soil chromium (Cr) accumulation is escalating, severely hindering plant growth and development. Plant growth-promoting bacteria (PGPB) have shown potential in enhancing plant tolerance to heavy metals. However, the role and mechanisms of Cr(VI)-reducing PGPB strains in improving the growth of pakchoi under Cr toxicity remain unclear. This study aimed to isolate a Cr(VI)-reducing PGPB strain from Cr-contaminated soil, evaluate its effect on pakchoi growth under Cr(VI) stress, and investigate the mechanisms involved. Our findings showed that Bacillus sp. NEAU-DCB1–2 effectively reduce Cr(VI) to Cr(III) and produced indole-3-acetic acid and siderophores. Under Cr(VI) stress, inoculation with NEAU-DC1–2 significantly promoted seed germination and early growth of pakchoi. In pot experiments, NEAU-DCB1–2 significantly increased biomass accumulation, plant height, and root length of Cr(VI)-treated pakchoi seedlings, while reducing the Cr(VI) content in root, shoot and soil. Moreover, NEAU-DCB1–2 greatly increased catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase activities in seedlings under Cr(VI) stress, thereby reducing malondialdehyde content. Transcriptome analysis indicated substantial alterations in gene expression patterns after inoculation with NEAU-DCB1–2 under Cr(VI) stress. Further analyses revealed that NEAU-DCB1–2 mainly affected the responses of antioxidant system, metal chelation and transport, together with auxin, abscisic acid, and jasmonic acid signaling to Cr(VI) stress. Conclusively, the Cr(VI)-reducing PGPB strain NEAU-DCB1–2 significantly enhances the growth and Cr tolerance of pakchoi through multiple mechanisms, offering a valuable microbial resource for mitigating the adverse effects of heavy metal contamination in agricultural soils on the yield and safety of vegetable crops.

De-Methyl Esterification Modification of Root Pectin Mediates Cd Accumulation of Lactuca sativa.

Cadmium (Cd) contamination in agricultural soil brings severe health risks through the dietary intake of Cd-polluted crops. The comprehensive role of pectin in lowering Cd accumulation is investigated through low Cd accumulated (L) and high Cd accumulated (H) cultivars of L. sativa. The significantly different Cd contents in the edible parts of two L. sativa cultivars are accomplished by different Cd transportations. The pectin is the dominant responsive cell wall component according to significantly increased uronic acid contents and the differential Cd absorption between unmodified and modified cell wall. The chemical structure characterization revealed the decreased methyl esterification in pectin under Cd treatment compared with control. Significantly brighter LM19 relative fluorescence density and 40.82% decreased methanol in the root pectin of L cultivar under Cd treatment (p < 0.05) supported that the de-methyl esterification of root pectin is more significant in L cultivar than in H cultivar. The pectin de-methyl esterification of L cultivar is achieved by the upregulation of pectin esterases and the downregulation of pectin esterase inhibitors under Cd treatments, which has facilitated the higher Cd-binding of pectin. Our findings provide deep insight into the differential Cd accumulation of L. sativa cultivars and contribute to the understanding the pollutant behaviors in plants.

Biochar and nanoscale silicon synergistically alleviate arsenic toxicity and enhance productivity in chili peppers (Capsicum annuum L.)

Arsenic (As) contamination in agricultural soils threatens crop productivity and food safety. In this study, we examined the efficacy of biochar (BC) and silicon nanoparticles (SiNPs) as environmentally sustainable soil amendments to alleviate As toxicity in chili (Capsicum annuum L.) plants. Our findings revealed that As stress severely inhibited the growth parameters of Capsicum annuum L., and subsequently reduced yield. However, the application of BC and SiNPs into the contaminated soil significantly reversed these negative effects, promoting plant length and biomass, particularly when applied together in a synergistic manner. Arsenic stress led to increased oxidative damage, as evidenced by a 29% increase in leaf malondialdehyde content as compared to the healthy plants. Nevertheless, the synergistic (BC + SiNPs) application effectively modulated antioxidant enzyme activity, resulting in a remarkable 55% and 66% enhancement in the superoxide dismutase and catalase levels, respectively, boosting chili's resistance against oxidative stress. Similarly, BC + SiNPs amendments improved photosynthesis by 52%, stomatal conductance by 39%, soluble sugars by 42%, and proteins by 30% as compared with those of control treatment. Additionally, the combined BC + SiNPs application significantly reduced root As content by 61% and straw As by 37% as compared with the control one. Transmission electron microscopy confirmed that the synergistic use of BC and SiNPs preserved chili leaf ultrastructure, shielding against As-induced damage. Overall, the supplementation of contaminated soil with BC and SiNPs was proved to be a sustainable strategy for mitigating As toxicity in chili peppers, enhancing plant growth, physiology, and yield, and thereby food safety.

Homocysteine S-Methyltransferase 3 Positively Regulates Cadmium Tolerance in Maize.

The increasing contamination of agricultural soils with cadmium (Cd) poses a significant threat to human health and global food security. Plants initiate a series of mechanisms to reduce Cd toxicity. However, the response of maize to Cd toxicity remains poorly understood. In this study, we identified that ZmHMT3, which encodes a homocysteine S-methyltransferases family protein, acted as a regulator of Cd tolerance in maize. Subcellular localization and in situ PCR exhibited that ZmHMT3 was localized in the cytoplasm and predominantly expressed in the phloem. Overexpression of ZmHMT3 enhanced Cd tolerance and reduced Cd concentration in both shoots and roots. In contrast, ZmHMT3 mutants attenuated Cd tolerance but did not change shoot Cd concentration. Heterologous overexpression of ZmHMT3 in rice enhanced Cd tolerance and reduced grain Cd concentration. Transcriptome analysis revealed that ZmHMT3 upregulated the expression of stress-responsive genes, especially glutathione S-transferases (GSTs) and transcription factors, including MYBs, NACs and WRKYs, and modulates the expression of different ATP-binding cassette (ABC) transporters, thereby enhancing Cd tolerance. Collectively, these findings highlight the pivotal role of ZmHMT3 in Cd tolerance and as a candidate gene for improving Cd tolerance in elite maize varieties.

Decreased Sulfamethoxazole Uptake in Lettuce (Lactuca sativa L.) due to Transpiration Inhibition by Polypropylene Microplastics

Microplastics and antibiotics are emerging contaminants in agricultural soil that can have negative effects on crops. However, limited research has been conducted on the effects of the polypropylene (PP) microplastic and sulfamethoxazole (SMX) co-exposure on crops, specifically regarding the impact of PP microplastics on SMX uptake and transport in crops. In this study, hydroponic experiments were carried out using lettuce (Lactuca sativa L.), PP microplastics (1.0 g L−1), and SMX (0.5 mg L−1 or 2.5 mg L−1) to investigate the individual and co-exposure effects of PP microplastics and SMX on Lettuce growth, explore the uptake and translocation of SMX in lettuce and elucidate the underlying mechanism of PP microplastic impact on SMX uptake. Results demonstrated that co-exposure to 1.0 g L−1 of PP microplastics and 0.5 mg L−1 of SMX resulted in an enhanced toxic effect. However, no intensified toxic effect on the lettuce was observed when 1.0 g L−1 PP microplastics were added in the presence of 2.5 mg L−1 SMX, indicating that the SMX dominated the toxic effect on lettuce at high concentrations. Additionally, the study found that the water absorption process controlled by the aquaporin and transpiration contributed to the uptake and translocation of SMX in lettuce. When exposed to PP microplastics, no impact was observed on the aquaporin contents of the lettuce while the transpiration rate was significantly decreased by 31.6 % - 44.2 % resulting from microplastics adhered to the root surface. Therefore, in the presence of 2.5 mg L−1 SMX, the SMX uptake in the lettuce root was inhibited by 35.9 % (P < 0.05) when exposed to 1.0 g L−1 PP microplastic. This work deepens our understanding of the behaviour of microplastics and antibiotics in the terrestrial environment.

Ameliorating arsenic and PVC microplastic stress in barley (Hordeum vulgare L.) using copper oxide nanoparticles: an environmental bioremediation approach

The present study investigates the impact of varying concentrations of PVC microplastics (PVC–MPs) – specifically 0 (no PVC–MPs), 2, and 4 mg L− 1 –alongside different arsenic (As) levels of 0 (no As), 150, and 300 mg kg− 1 in the soil, with the concurrent application of copper oxide–nanoparticles (CuO–NPs) at 0 (no CuO –NPs), 25 and 50 µg mL− 1 to barley (Hordeum vulgare L.) plants. This research primarily aims to assess plant growth and biomass, photosynthetic pigments and gas exchange characteristics, oxidative stress indicators, as well as the response of various antioxidants (both enzymatic and non-enzymatic) and their relevant genes expression, proline metabolism, the AsA–GSH cycle, and cellular fractionation within the plants. The findings showed that increased levels of PVC–MPs and As stress in the soil significantly reduced plant growth and biomass, photosynthetic pigments, and gas exchange characteristics. Additionally, PVC–MPs and As stress increased oxidative stress in the roots and shoots, as evidenced by elevated levels of malondialdehyde (MDA), hydrogen peroxide (H2O2), and electrolyte leakage (EL), which in turn stimulated the production of various enzymatic and non-enzymatic antioxidants, gene expression, and sugar content. Furthermore, a notable increase in proline metabolism, the AsA–GSH cycle, and cellular pigmentation was observed. Conversely, the application of CuO–NPs resulted in a substantial improvement in plant growth and biomass, gas exchange characteristics, and the activity of enzymatic and non-enzymatic antioxidants, along with a reduction in oxidative stress. Additionally, CuO–NPs enhanced cellular fractionation while decreasing proline metabolism and the AsA-GSH cycle in H. vulgare plants. These outcomes provide new insights into sustainable agricultural practices and offer significant potential in addressing the critical challenges of heavy metal contamination in agricultural soils.

The role of selenium and biochar nanoparticles in alleviating cadmium stress in wheat (Triticum aestivum L.) examined via morphophysiological traits and organic acid exudation patterns

Nanotechnology is capturing great interest worldwide due to their stirring applications in various fields and also individual application of selenium (Se) and biochar nanoparticles (BC−NPs) have been studied in many literatures. However, the combined application of Se and BC−NPs is a novel approach and studied in only few studies. For this purpose, a pot experiment was conducted to examine various growth and biochemical parameters in wheat (Triticum aestivum L.) under the toxic concentration of cadmium (Cd) i.e., 50 mg kg−1 which were primed with combined application of Se and BC−NPs i.e., 10 mg L−1. Our results showed that the Cd toxicity in the soil showed a significant declined in the growth, gas exchange attributes and nutrient uptake in T. aestivum. However, Cd toxicity significantly increased oxidative stress biomarkers, organic acids, enzymatic and non-enzymatic antioxidants including their gene expression in T. aestivum. Although, the application of Se and BC−NPs showed a significant increase in the plant growth and biomass, gas exchange characteristics, nutrient uptake, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress and Cd uptake in different parts of the plant. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

Spatial and Bioaccumulation of Heavy Metals in a Sheep-Based Food System: Implications for Human Health.

Heavy metal contamination in agricultural soils presents serious environmental and health risks. This study assessed the bioaccumulation and spatial distribution of nickel, cadmium, zinc, lead, and copper within a sheep-based food chain in the Baia Mare region, Romania, which includes soil, green grass, sheep serum, and dairy products. Using inductively coupled plasma mass spectrometry (ICP-MS), we analyzed the concentrations of these metals and calculated bioconcentration factors (BCFs) to evaluate their transfer through trophic levels. Spatial analysis revealed that copper (up to 2528.20 mg/kg) and zinc (up to 1821.40 mg/kg) exceeded permissible limits, particularly near former mining sites. Elevated lead (807.59 mg/kg) and cadmium (2.94 mg/kg) were observed in industrial areas, while nickel and cobalt showed lower concentrations, but with localized peaks. Zinc was the most abundant metal in grass, while cadmium transferred efficiently to milk and cheese, raising potential health concerns. The results underscore the complex interplay between soil properties, contamination sources, and biological processes in heavy metal accumulation. These findings highlight the importance of continuous monitoring, risk assessment, and mitigation strategies to protect public health from potential exposure through contaminated dairy products.

Biochar solutions: Slow and fast pyrolysis effects on chromium stress in rapeseed roots

Chromium (Cr) contamination in agricultural soils, largely due to industrial activities, poses a significant threat to plant growth and productivity. This study examines the effects of Cr stress at concentrations of 100 and 200 mg of K2Cr2O7 per kg soil on rapeseed (Brassica napus) roots and evaluates the mitigating potential of biochar. Biochar, produced through both slow and fast pyrolysis and applied at 30 g per kg soil, was investigated for its ability to neutralize Cr toxicity. Our findings indicate that Cr stress significantly decreased the growth and physiological functions of rapeseed roots. However, biochar application improved soil pH, cation exchange capacity, and the uptake of essential nutrients such as nitrogen, phosphorus, potassium, calcium, and magnesium. Additionally, biochar enhanced the production of osmotic regulators like glycine betaine and soluble proteins, as well as indole acetic acid, promoting better root growth and water uptake under Cr stress. Notably, biochar reduced Cr availability and absorption in rapeseed roots, leading to lower levels of stress-related hormones such as abscisic acid, salicylic acid, and jasmonic acid. Among the biochars tested, slow pyrolysis biochar was more effective than fast pyrolysis biochar in mitigating Cr toxicity. These results highlight the potential of slow pyrolysis biochar as a sustainable strategy to alleviate Cr pollution and enhance plant resilience in contaminated soils.

Transect approach for assessing major and trace elemental contamination in agricultural soils of the palamaner division, chittoor district, andhra pradesh, india.

Three soil transects located in the granitic regions of Palamaner mandal, Andhra Pradesh, India, were examined to assess the pollution levels of both primary and secondary metals (Si, Al, Fe, Ca, Mg, Na, K, Cu, Mn, P, and Zn) and to ascertain the degree of soil pollution in agricultural areas. The soils along these transects are slightly acid to neutral, with dark brown to red rubified argillic clay-rich B horizons alongside a moderate cation exchange capacity. The A horizon soils display low organic carbon levels with a moderate variability and contain over 70% SiO2, exhibiting low variability due to limited leaching in a semiarid climate. The findings suggest that iron (Fe) and manganese (Mn) oxides play a role in reducing contamination levels through oxidation and precipitation processes. Furthermore, the soils show low to moderate cation exchange capacity, which restricts the retention of absorbed heavy metals, thus lessening their negative impacts. A two-way ANOVA revealed significant differences in CEC, organic carbon, and total zinc content across different horizons and landscape positions. Si, Al, and Cu had small increases and negative geoaccumulation indices in all soil profiles, suggesting no pollution. However, the Nemerow and mean contamination degree over 6 point to slight to moderate pollution. The analysis identified three distinct clusters with significant variations in contamination factors for SiO2 and Cu. Five principal components were determined, explaining 76% of the total variance, primarily derived from geogenic sources and remaining within acceptable limits. This research on soil transects in granitic regions contributes to a better understanding of the distribution, movement, and concentration of elemental oxides based on slope position, which is essential for pollution assessment and soil quality enhancement.

Nanopriming with phytofabricated selenium nanoparticles alleviates arsenite-induced oxidative stress in Spinacia oleracea L.

Arsenic (As) contamination of agricultural soil has become a major concern due to its adverse effects on plant growth and human health. Selenium nanoparticles (SeNPs), a novel selenium (Se) source, are characterised by their exceptional biocompatibility, degradability, and bioactivities. In the present study, SeNPs were biogenically synthesised and further characterised using UV-visible spectroscopy, XRD, FTIR, and TEM analysis. Different concentrations of the synthesised SeNPs were used to treat Spinacia oleracea L. (spinach) seeds to determine their impact on growth profile, gas exchange, photosynthetic pigments, oxidative stress, and antioxidant enzyme status upon arsenite (AsIII) treatment. The findings revealed that SeNP supplementation at a concentration of 100µM (SeNPs100) led to a significant reduction in As accumulation by twofold in roots and 1.5-fold in leaves when compared to plants exposed to AsIII100 (µM) alone. Interestingly, the photosynthetic efficiency was also remarkably enhanced upon SeNPs100 treatment, associated with increased activities of the defence enzymes (ascorbate peroxidase, catalase, and glutathione peroxidase) in the AsIII + SeNP-exposed spinach plants as compared to AsIII treatment alone. Overall, the present study highlights the potential of biogenic SeNP supplementation in promoting plant growth and mitigating As toxicity in spinach under AsIII stress. This study could have significant implications for the use of SeNPs as a nanofertiliser in regions grappling with As-contaminated soils for sustainable agriculture and human health.

Engineered biochars for simultaneous immobilization of as and Cd in soil: Field evidence

Agricultural soil contamination by potentially toxic elements (PTEs) such as arsenic (As) and cadmium (Cd) poses a serious threat to food security. Immobilization serves as a widely used approach for the remediation of PTEs contaminated soils, nevertheless, the long-term effectiveness for the simultaneous immobilization of both cations and oxyanions remains a challenge. In order to effectively enhance the synergistic immobilization effect of soil As and Cd contaminated by multiple elements and improve the ecological environment of farmland. In this study, a typical polluted tailings area farmland was selected for situ immobilization experiments, and biochar was prepared from cow manure (CMB), rice straw (RSB), and pine wood (PWB) as raw materials. On this basis, the pristine biochar was modified with ferric chloride (F), potassium permanganate (K), magnesium chloride (M), and aluminum chloride (A), respectively. Furthermore, the immobilization effect of modified biochar on As-Cd and the stress effect on soil respiration were investigated. The results showed that CMB and RSB reduced the bioavailability of heavy metals, potassium permanganate has strong oxidizing properties, and the strong oxidability of potassium permanganate stimulated the generation of more oxygen-containing functional groups on the surface of biochar, thereby enhancing the adsorption and complexation effect of modified materials on As and Cd. Among them, the extracted Cd concentration of Diethylenetriamine pentaacetic acid (DTPA) in KCMB and KRSB in 2020 decreased by 8.23–43.12% and 9.67–35.29% compared to other treatments, respectively. Meanwhile, the KCMB and KRSB treatments also reduced the enrichment of As and Cd in plant tissues. In addition, the dissolved organic carbon (DOC) content in KCMB treatment was relatively high, and the carbon stability of the material was weakened. Simultaneously, the soil respiration emission of KCMB treatment was increased by 5.63% and 11.93% compared to KRSB and KPWB treatments, respectively. In addition, the structural equation also shows that DOC has a large positive effect on soil respiration. In summary, the KRSB treatment effectively achieve synergistic immobilization of As-Cd and provide important guiding significance for green and low-carbon remediation of polluted farmland.