Search Results (225)

Land use conversion profoundly affects the ecological functioning of reclaimed soils. However, the coupling mechanisms among soil nutrient accumulation, heavy metal dynamics, and microbial diversity under different land use types remain unclear. This study investigated reclaimed mining soils under five land use types to evaluate changes in soil properties, heavy metal distribution, and bacterial diversity, and to elucidate their regulatory mechanisms. Wheat fields and Ligustrum plantations showed higher carbon, nitrogen, and phosphorus contents, with increased lead and arsenic concentrations, whereas abandoned grasslands exhibited relatively lower nutrient availability. Land use explained 26.4% of bacterial community variation (R² = 0.264, p = 0.001). Structural equation modeling revealed that nutrient enrichment significantly promoted heavy metal accumulation (β = 0.606, p < 0.001). Nutrients negatively affected bacterial richness (β = −0.401, p = 0.035). In contrast, moderate metal stress may promote microbial richness (β = 0.460, p = 0.015) through micronutrient effects or hormesis (low-dose toxic stimulatory response). These findings indicate that land use conversion regulates microbial diversity through coupled changes in nutrient availability and metal dynamics. Reclamation strategies should integrate nutrient management, vegetation selection, and heavy metal risk assessment to achieve long-term restoration of soil functions. Full article

The Qinghai–Xizang (Formerly Tibet) Plateau, known as the Roof of the World, is an important ecological security barrier for Asia and globally; its natural environment is fragile and challenging to repair after destruction. Prior to the 21st century, waste management in China primarily relied on unregulated direct dumping. To investigate the environmental impacts of open dumpsites in high-altitude regions, this study focused on a representative dumpsite in the northern Xizang region. The aim was to characterize the occurrence and distribution patterns of heavy metals (HMs) in its surrounding soil, conduct source apportionment, and perform comprehensive risk assessment. The results showed low levels of mercury (Hg) and excessive levels of all other HMs. In addition, all HMs had the highest content in the residual fraction and the lowest content in the weak-acid fraction, which is less bioavailable. The Absolute Principal Component Score–Multiple Linear Regression (APCS-MLR) and Positive Matrix Factorization (PMF) results showed that the dumpsite contributed the most to cadmium (Cd); agricultural sources contributed the most to zinc (Zn); Hg mainly came from atmospheric transport and traffic sources; Pb was mainly derived from traffic and natural sources; and copper (Cu), nickel (Ni), chromium (Cr), and arsenic (As) mainly came from the dumpsite and natural sources. In addition, this research found that this dumpsite poses a relatively high HM risk to human health; oral and respiratory routes are the main non-carcinogenic routes, As and Cr contribute more to the adult and child groups, and As contributes the most to carcinogenic risk. The calculation results of the pollution assessment method indicate that the pollution of the natural environment from this dumpsite is at a low level, and immediate remediation measures are urgently needed to achieve site decontamination. Full article

Juniperus species form critical, long-lived high-mountain forest ecosystems in Central Asia, serving essential phytocoenotic and ecological functions in environmentally challenging habitats. However, the relationships between the elemental composition of these evergreen conifers and their underlying soils remain poorly understood. This study evaluated and compared the distribution of major elements (Fe, Ca, P, Mg, Al, Na, K, S), trace elements (Cu, Pb, Zn, Ni, Co, Mn, As, Cd, Cr, Mo, U, Th, Sr, Sb, Bi, V, La, Ba, Ti, B, W, Sc, Zr, Tl, Ta, Nb, Se, Te, Ga, Cs, Ge, Hf, Rb, Sn and others), and environmental pollution indices (Igeo, EF, CF, BAF) in plant tissues (leaves and cones) and canopy soils of three key juniper species (Juniperus seravschanica, J. turkestanica, and J. semiglobosa) in the Fann Mountains, Tajikistan. Soil and plant samples were collected across natural habitats and analyzed for total chemical composition using ICP-OES. The soils showed a near-neutral reaction (pH 7.02–7.42 in H₂O and 6.41–7.15 in KCl), with considerable variability in Corg. content (5.04%–21.82%) and Nt content (0.337%–1.149%) in the humus (A) horizons. Geochemical indices (Igeo up to 2.42, EF up to 35.30) indicated noticeable soil enrichment and localized contamination by arsenic (As) and cadmium (Cd), likely driven by a combination of regional industrial and mining activities alongside natural geogenic enrichment. Across all sites, elemental concentrations followed a consistent sequence: soil > leaves ≈ cones. Heavy metals in plant tissues remained well below toxic thresholds. High organ-specific partitioning was observed: K predominated in cones (K > Ca > P), whereas Ca and Fe accumulated predominantly in leaves (Ca > K). Low bioaccumulation factor values (BAF < 1) indicate limited element accumulation relative to total soil concentrations for all three species, which may be influenced by both reduced bioavailability in neutral-to-alkaline soils and potential physiological regulation. As the first data reported from this region, these findings establish an essential baseline for long-term ecological monitoring, soil–plant chemistry, conservation, and environmental risk assessment in the Fann Mountains’ juniper ecosystems. Full article

This study analyzed the content of polluting and toxic elements (Cr, Ni, Cu, Zn, As, Cd and Pb) in the cadastral municipalities immediately surrounding the mining and metallurgical complex Bor in Serbia. The soil is exposed to hazardous substances due to historical pollution. Soil pollution at different locations was assessed based on the measured concentration of metals and the contamination factor (Cf). The increased content of the toxic metals was determined mostly for copper and arsenic. Three types of different plants were used in order to reduce the content of toxic metals in the contaminated mining and metallurgical land. The results showed that these plants (barley Hordeum sativum, sugar grazer Sorghum bicolor, and hybrid BMR 333 Sudan grass) were capable of growing and accumulating metals in plants at copper-mined and metallurgical sites. Full article

Microbially induced calcium carbonate precipitation (MICP) is a promising biotechnology for environmental remediation; however, the high cost of conventional chemical-grade calcium sources limits its large-scale scalability. This study evaluated the feasibility of utilizing an aqueous extract of natural attapulgite clay as a sustainable, low-cost calcium source for MICP-mediated arsenic (As) immobilization in both aqueous and soil systems. Among the tested minerals, Baiyin attapulgite (group B) exhibited the highest calcium content (62,808.94 mg kg⁻¹) and minimal toxic metal impurities, providing a favorable chemical matrix for biomineralization. At an optimal solid-to-liquid ratio of 1:10, Lysinibacillus fusiformis LF and Enterococcus LZU-1 successfully induced calcite precipitation driven by the attapulgite extract. In batch aqueous remediation experiments (20 days), the attapulgite extract significantly enhanced As removal efficiency compared to the controls; As removal rates peaked at 66.4% for strain LZU-1 (with LZ1 extract) and 65.8% for strain LF (with group B extract), drastically outperforming the standard CaCl₂ groups (31.2–37.3%) and blank controls (21.8–24.5%). Concurrently, soil incubation experiments (30 days) demonstrated that the combined application of attapulgite and MICP bacteria reduced the highly bioavailable exchangeable As fraction from 0.115 to approximately 0.03 mg kg⁻¹, while effectively driving its transformation into more stable carbonate-bound and organic-bound fractions without causing secondary soil salinization. Morphological and mechanistic analyses revealed that, compared to the well-defined euhedral crystals in the CaCl₂ control, the precipitates mediated by the clay extract exhibited distinctly irregular, defect-rich rhombohedral structures. This structural disruption was governed by the natural matrix effect of attapulgite, which simultaneously supplied dissolved Ca²⁺ and provided an abundance of fine clay fragments, calcite micro-grains, and associated amorphous Fe/Al/Mn-bearing phases. These constituents acted as physical scaffolding and heterogeneous nucleation sites that became embedded in the growing CaCO₃ lattice, driving the formation of highly reactive, defect-rich clay-calcite-arsenic composite precipitates that efficiently encapsulated arsenate. Mantel analysis further revealed that the remediation efficiency was significantly correlated with key environmental variables including Ni, V, Ca. These findings highlight the dual-system potential of natural attapulgite as an inexpensive, eco-friendly calcium alternative for sustainable MICP-based remediation of As-contaminated water and agricultural soils. Full article

Since 2011, Caribbean and West African countries have experienced the deposit of millions of tonnes of the pelagic brown seaweed sargassum. While these algal blooms are well documented in the Caribbean, less information is available on the occurrence, monitoring and composition of sargassum biomass in West Africa. Cabo Verde (CV), one of the volcanic archipelagos of the Macaronesia region, has experienced sargassum beaching events since 2022, with 2025 being the worst year so far. In this study, high quantities of biomass that were beached in December 2025 (>100 tonnes) were determined in two locations in Santiago—CV’s largest island. Additionally, samples taken in 2024 were analysed to explore the potential valorisation of pelagic sargassum in CV. Elemental composition, amino acid profiling and calculation of NPK ratio suggested that this biomass could be processed for applications towards sustainable agriculture, providing benefits for local development. However, processes would have to include low cost and efficient pre-treatment(s) to manage the content of toxic elements (arsenic, cadmium, and lead). The development of sargassum-derived products for soil amelioration and improvement of crop production could contribute to strengthening communities and empowering local women’s groups, who play key roles in Cabo Verdean agriculture and rural economy. Full article

Agricultural soil contamination by potentially toxic elements is a global concern due to its impacts on food safety and human health, yet comprehensive assessments remain limited in many regions of Ethiopia. This study provides an integrated assessment of PTE contamination in agricultural soils of the North Gondar Zone, Ethiopia, by evaluating physicochemical properties, pollution levels, and human health risks. Soil parameters, including pH, electrical conductivity, organic carbon, organic matter, moisture content, total nitrogen, and available phosphorus, varied among sampling sites. Soil pH ranged from moderately acidic to near-neutral, indicating variations in soil acidity likely associated with differences in moisture content, organic matter, and land management practices, while electrical conductivity values indicated non-saline conditions suitable for agriculture. Concentrations of PTEs (As, Zn, Cd, Pb, and Hg) were generally within permissible limits established by WHO and FAO. Pollution indices revealed predominantly natural background levels for As, Zn, Cd, and Pb, whereas Hg exhibited moderate to strong contamination, with the Geoaccumulation Index and Contamination Factor identifying Hg as the primary environmental risk element. Non-carcinogenic risk assessment showed that hazard quotients and hazard indices for both adults and children were below 1, indicating negligible health risks. Carcinogenic risk assessment demonstrated that all calculated risks were within the acceptable range (10⁻⁶–10⁻⁴), although children showed higher total cancer risk (TCR) values than adults due to greater exposure intensity and lower body weight. Arsenic was identified as the dominant contributor to carcinogenic risk across all sampling sites. The findings demonstrate that agricultural soils in the study area are generally safe with respect to the investigated PTEs; however, Hg contamination indices indicate a potential environmental concern requiring continued monitoring. Sustainable soil management practices, including effective pH management and liming of strongly acidic soils (pH < 5.5), are recommended to improve soil quality, reduce PTE mobility and bioavailability, and minimize future accumulation of hazardous elements while maintaining agricultural productivity. Full article

Heavy metal (HM) contamination near mining operations in Kazakhstan poses a serious threat to the environment. However, data on the state of chernozem soils in this region is limited. This study assessed the bioaccumulation of HMs and translocation within the soil–sunflower (Helianthus annuus L.) system in a southern Calcic Chernozem in the Kostanay region (Northern Kazakhstan), which is located 50 km from the nearest mining facility. The content of seven HMs (Cd, Co, Cr, Cu, Ni, Pb, and Zn) and arsenic (As), as well as five macroelements (K, Ca, S, Mg, and P), was determined in 18 soil samples from the complete soil pedon (0–150 cm) and in eight anatomical parts of six sunflower plants at physiological maturity. Most metals exhibited a deficiency relative to upper continental crustal Clarke values (Clarke of Concentration (CC) < 1 for Cr, Cu, Ni, Pb, and Zn), with a moderate lithogenic anomaly for Cd (CC = 1.65–3.57) and a localized Co anomaly in the Bk horizon (56.26 mg kg⁻¹), indicating no pronounced HM contamination at the investigated agricultural site. Metal distribution exhibited strong organ specificity in sunflower plants. Cd, Cu, and Zn accumulated preferentially in the leaves, whereas Ni and Co were more concentrated in the seeds and stems, respectively. Only cadmium exceeded the threshold values for both BCF > 1 (1.01) and TF > 1 (1.47), confirming the status of sunflower as a cadmium accumulator. These results provide a preliminary reference dataset of the organ-specific distribution of heavy metals in H. annuus L. plants, which can serve as a local baseline for sunflower growth in uncontaminated southern Chernozems. This information can contribute to future environmental monitoring purposes in the region, acting as an exploratory benchmark. Full article

Rice production is under increasing threat from adverse climatic trends that exacerbate water scarcity and compromise food safety. The need to transition toward water-saving irrigation is urgent, as is the requirement of addressing the dual burden of selenium (Se) deficiency and arsenic (As) toxicity. This 3-year field study (2020–2022) is the first to evaluate the effects of integrated water-saving irrigation. Permanent flood irrigation (Flood) or alternate wetting and drying was used, in which fields were reflooded when the soil matric potential reached −20 kPa (Reflood-20) and −70 kPa (Reflood-70); the effects of foliar Se biofortification at 15 g Se ha⁻¹ with sodium selenate (15-Se) or no Se (No-Se) on rice production and Se and As accumulation were also investigated. The results identified the Reflood-20 regime as the optimal strategy, achieving 36% water savings without significant grain yield penalties while enhancing grain quality. Foliar Se application successfully increased the dehulled grain Se content by 10.7-fold, effectively meeting human dietary requirements. The As contents were decreased by 27.6% due to water restriction, and an additional 10% loss was observed because of Se supplementation. Analysis of the straw also showed a 23.5% decrease in As and a 5.7-fold increase in Se. Consequently, the synergy between moderate deficit irrigation and Se biofortification provides a robust, cost-effective framework for the large-scale production of safer, nutrient-dense rice, reconciling resource efficiency with food security. Full article

Arsenic represents a ubiquitous element in the environment, characterized by high mobility, complex chemical speciation and a strong sensitivity to redox conditions and biological activity, with microbial processes play a central role in its biogeochemical cycling. The present review provides a comprehensive and integrative synthesis of arsenic biogeochemical cycling across terrestrial, freshwater and marine environments, in which chemical speciation is explicitly treated as the central unifying concept controlling arsenic mobility, transformation and bioavailability, linking geological, chemical and biological processes across environmental compartments. Natural processes regulating arsenic distribution are examined from mineralogical sources and soil–water interactions to biologically mediated transformations in aquatic and marine biotic compartments, largely driven by microbial activity, highlighting the contrast between inorganic arsenic dominance in abiotic reservoirs and the prevalence of organoarsenicals in tissues of living organisms. The review further explores arsenic behaviour under natural environmental alterations and in extreme or unconventional ecosystems, where redox constraints, sulphide chemistry or intense fluid–sediment exchanges lead to deviations from the baseline speciation patterns. Against this framework, anthropogenic perturbations are discussed through several documented case studies, illustrating how industrial releases, the long-term effects of mining activities, agricultural practices and the use of synthetic arsenical compounds may change arsenic pathways primarily by altering geochemical and biological controls rather than through a generalized increase in total arsenic content. Overall, the topics covered provide an integrated framework for interpreting arsenic dynamics across environmental systems, emphasizing the complex biogeochemical processes governing arsenic cycling. Full article

Lysobacter antibioticus Hz25 is a novel strain that was isolated from the rhizosphere of the relict endemic plant Hedysarum zundukii Peschkova (Fabaceae), which grows on carbonate soils in the Baikal region of Russia. This work presents the complete genome sequence of Hz25 (5.98 Mb, 66.94% GC), which was obtained using a hybrid assembly method combining Oxford Nanopore and Illumina sequencing. Phylogenetic analysis based on 47 Lysobacter genomes and an average nucleotide identity (ANI) value of 96% confirmed its affiliation with L. antibioticus. A comparative pan-genome analysis with three closely related strains (13-6, 76, and ATCC 29479) identified 554 strain-specific genes. This significant genomic plasticity likely reflects adaptation to the sharply continental climate, high insolation, and low free iron content of the native soil. The genome encodes a comprehensive micropredator arsenal, including: seven chitinase genes (GH18 and GH19 families); bacteriolytic enzymes (Blp, L1, L4, Ami); a complete type III secretion system (T3SS) with predicted effectors; type IV pili (including the PilZ-PilB regulatory complex); and siderophore biosynthesis genes (lysochelin). The genome contains genes ars of an arsenic resistance system, but lacks the ACR3 efflux pump, suggesting that these genes may have alternative functions. Genes involved in calcium homeostasis (Excalibur domain, Na⁺/Ca²⁺ antiporter) were also identified. These features make Hz25 a promising candidate for biocontrol applications in cold climates and metal-contaminated environments. Full article

Nanoplastics (NPs) are increasingly detected in agricultural soils, yet their influence on arsenic (As) transfer and plant toxicity remains unclear. Lettuce (Lactuca sativa L.) was cultivated in farmland soil with a naturally high As background (98.8 mg·kg⁻¹) to assess how polyethylene nanoplastics (PE NPs) affect rhizosphere conditions, As accumulation, and plant performance. PE NPs partially buffered soil acidification but reduced rhizosphere water content, while total soil As remained largely unchanged. Leaf As increased by 35–39%, with reduced biomass (up to 30%) and lower chlorophyll status (SPAD ~7% lower). Metabolomic analyses indicated dose-dependent alterations in central carbon metabolism and phenylalanine-related antioxidant metabolites, including suppressed tricarboxylic acid cycle intermediates at higher PE levels. Overall, PE NPs enhanced transfer of background As to edible leaves and intensified phytotoxicity, underscoring the need to consider nanoplastics in risk assessment of As-affected soils. Full article

Phytoremediation is a prevalent approach for addressing remediation and production goals in polluted agricultural land. In this study, we examined the impact of four distinct planting ratios on crop growth, accumulation of arsenic (As), and rhizosphere soil dynamics of peanut and maize. The results revealed that intercropping significantly reduced grain As accumulation (42.11–63.16% in maize; 62.28% in peanut under the 1:2 ratio, T2), achieving compliance with Chinese food safety standards (GB 2762-2017, 0.05 mg kg⁻¹). Meanwhile, the T2 treatment exhibited a significantly higher As bioconcentration factor (BCF) and the lowest translocation factor (TF). The metal removal equivalent ratio (MRER) under different planting systems was 1.09, 2.41, 1.07, and 1.46. Additionally, while intercropping did not increase grain biomass per plant, the LER values > 1 for T1 (1.88) and T2 (1.25) demonstrated that complementary resource use enhanced total productivity. Intercropping treatments significantly affected soil properties in both maize and peanut rhizospheres. For maize, intercropping lowered soil pH and available As content but increased dissolved organic carbon (DOC). Notably, only the T1 treatment significantly reduced the cation exchange capacity (CEC) of maize soil. Peanut’s rhizosphere experienced increases in both pH and CEC due to intercropping, with only the T2 treatment yielding a slight rise in DOC. The findings suggest that the maize–peanut intercropping system, especially the T2 system, effectively alters the soil–plant interface to limit As uptake while maintaining productivity, demonstrating its promise for safe utilization of As-contaminated land. Full article

Arsenic (As) pollution has become a global concern, and the search for effective and sustainable As remediation methods has attracted much attention. Sustainable and cost-effective technologies for As remediation are essential to protect public health. This study aligns with the United Nations Sustainable Development Goals (SDGs), specifically SDG 6 (Clean Water and Sanitation) and SDG 12 (Responsible Consumption and Production), by transforming agricultural waste into value-added biochar for environmental remediation. Currently, studies on the remediation of As pollution using iron-modified biochar (Fe-BC) and cerium-modified biochar (Ce-BC) have demonstrated promising application potential. Although there is an established research foundation regarding their remediation performance and mechanisms, comparative studies evaluating their performance and mechanisms under unified experimental conditions remain limited. As in this study, Fe-BC and Ce-BC were prepared and systematically investigated. The As remediation performance and mechanisms of the two biochars were compared and analyzed through material characterization, aqueous adsorption experiments, and soil remediation assessments. The results showed that the specific surface areas of Fe-BC and Ce-BC were 94.380 m²·g⁻¹ and 36.388 m²·g⁻¹, respectively, both higher than that of the original biochar (BC). The Langmuir and Freundlich models adequately fitted the As adsorption processes of all three materials. Fe-BC and Ce-BC exhibited a tendency toward monolayer adsorption for As(III). The Freundlich distribution coefficient K_F of Fe-BC was 0.1604, which was higher than that of BC and Ce-BC, indicating superior adsorption performance for As(III). In the pot experiment, when Fe-BC and Ce-BC were applied at 5%, the As content in ryegrass decreased by 78.38% and 77.15%, respectively. Fe-BC reduced the available As content in soil by 63.1% and decreased As accumulation in ryegrass by 78.38%. The reduction in available As content achieved by Fe-BC was greater than that achieved by Ce-BC. Fe(III) oxides supported on Fe-BC immobilized As through complexation and precipitation mechanisms. Fe⁰ and Fe₃O₄ in the materials altered the redox potential of the local microenvironment, affecting the transformation and stabilization of As species. Ce-BC primarily oxidized As(III) to As(V), and Ce⁴⁺ facilitated the formation of CeAsO₄ precipitates due to its high redox potential. Full article

Irrigation with pig slurry has been employed to discharge large volumes of slurry and to recover resources. However, using swine wastewater for agricultural irrigation may cause the accumulation of heavy metals in soil and their potential leaching to groundwater. Wastewater treatment plants (WWTPs) are crucial to mitigate heavy metal contents in swine wastewater through physical, chemical, and biological processes. This study tracked the fate of eight heavy metals in industrial swine farms: arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), mercury (Hg), nickel (Ni), and zinc (Zn). Zn reported the highest removal (82 to 99%) in all WWTPs and Cu the lowest (−5 to 97%). Cu (0.59–1.64 mg L⁻¹) and Zn (0.35–1.14 mg L⁻¹) were the metals reported in all samples for the target treatment stages (influent, after biodigester, and effluent). Comparing the heavy metal concentration in the effluents, Cu and Zn reached the highest concentrations in all WWTPs. As, Cd, and Pb reported values under the practical quantification limit. In groundwater, Cr reported the highest average concentration in farm GP19 for upstream (0.006 mg L⁻¹) and for downstream (0.032 mg L⁻¹) in GP1. In irrigated soil the Cu and Zn reported the highest concentrations in all farms, showing an enrichment compared to natural soil, indicating that wastewater is the main source of these metals in soil in the farm areas. Although all metals met the Mexican and international regulations, total suspended solids (TSSs) and chemical oxygen demand (COD) for effluent were above the reference limits (TSS ≤ 24 mg L⁻¹ and COD ≤ 72 mg L⁻¹) more than ten and four times, respectively, for all WWTPs evaluated. These two parameters were positively related and significantly correlated (p < 0.05) with the presence of metals in the different water fractions, implying possible transport of metals in solids. Cd, Pb, and As, were never reported in treated wastewater and groundwater, but Cr and Hg were. This may be related to external activities such as agriculture for Cr. The enrichment of metals in irrigated soils can be related to the metal presence in groundwater due to leaching because of the karstic soil in the area. Full article