Search Results (1,421)

The long-term release of heavy metals from inactive tailing ponds poses a persistent threat to groundwater quality, yet the effectiveness of commonly employed risk control measures—such as anti-seepage liners and chemical stabilization—remains insufficiently evaluated under realistic field conditions. This study aims to assess the effectiveness of risk control strategies at a Pb Zn mine tailing pond in Yunnan Province, China. A dynamic 2D numerical pollutant transport model was developed, calibrated, and validated against observed hydraulic heads and metal concentrations from monitoring wells within the study aquifer. The calibrated model showed good agreement with field measurements. Simulation results indicate that anti-seepage liners alone are insufficient to ensure compliance with the Class III standards of the Chinese Groundwater Quality Standards, even under ideal conditions where all leaching from the tailing pond is prevented. In contrast, a combined strategy—chemical stabilization reducing Pb leaching from historically contaminated soils (initial Pb: 183 µg L⁻¹) by at least 70%, together with anti-seepage systems reducing infiltration flux by over 94.4%—would be sufficient to restore groundwater quality to within regulatory limits. Full article

The co-pyrolysis of waste sawdust and non-recyclable polypropylene at 500 °C was investigated for low-cost adsorbent production and solid waste valorization in rural Thailand. Sustainability was evaluated through techno-economic analysis, gate-to-gate environmental screening, CO₂ emission accounting, adsorption cost analysis, and social return on investment assessment. The sawdust–polypropylene biochar produced at 500 °C production system requires a total capital expenditure of 46,000 THB and achieves a unit production cost of 316 THB kg⁻¹ at a 35% w/w biochar yield, 7–14 times lower than commercial granular-activated carbon and powdered-activated carbon. Based on a hypothetical community-scale deployment scenario, the estimated capital expenditure payback period under in-house granular-activated carbon substitution falls below six months. All annual techno-economic and SROI results presented in this study represent scenario-based screening estimates and should not be interpreted as demonstrated community-scale performance. Gate-to-gate environmental screening estimated gross production emissions of 8.771 kg CO₂e kg⁻¹ SPB-500. A consequential waste-diversion scenario incorporating carbon sequestration and avoided-disposal credits yielded a hybrid scenario-based net greenhouse-gas balance of +3.082 kg CO₂e kg⁻¹ SPB-500, supporting its potential application under the evaluated scenario of approximately 0.4–5.9 kg CO₂e kg⁻¹ relative to commercial-activated carbon benchmarks. Social return on investment analysis yields a base–case ratio of 1.39:1 (five-year total present value: 6,025,841 THB; minimum across sensitivity scenarios: 1.13:1), with water quality improvement (SDG 6; 46.1%) and health risk reduction (20.7%) jointly accounting for 66.8% of monetized outcomes, confirming investment justification from public health benefits alone. Quantifiable alignment is demonstrated across five UN Sustainable Development Goals. Collectively, these findings suggest that SPB-500 co-pyrolysis has the potential to be an economically accessible and socially beneficial waste-valorization technology under the evaluated scenario, supporting its potential application in decentralized heavy-metal remediation in resource-constrained communities. Full article

Heavy metal pollution has become a critical concern in agricultural ecosystems driven by a complex matrix of industrial practices, high-input fertilizers, metal-based agrochemicals, and wastewater irrigation. While the previous literature typically highlights general physiological symptoms of heavy metal stress, this review provides a novel, comprehensive framework that bridges three independent pillars: specific industrial applications dictating elemental pathway, localizes active root-zone transport kinetics, and an engineering-based evaluation of emerging remediation strategies. We systematically synthesized literature from 2000 to 2026 across major databases (WoS, PubMed and Google Scholar), applying strict inclusion criteria based on data validation, experimental reproducibility, and mechanistic depth. We examine the geochemical behavior, cellular toxicity, and plant resilience mechanics of seven priority elements like cadmium, lead, arsenic, aluminum, mercury, chromium and molybdenum. Rather than merely reiterating superficial visual damage like chlorosis or stunted growth, we focus on physiological and molecular root causes of phytotoxicity, including the structural hijacking of essential nutrient networks, intracellular reduction cascades and organelle-specific oxidative disruption. This review also discussed the discovery of specialized, energy-dependent eukaryotic transport mechanisms like ABC transporters and a comparative operational blueprint evaluating physical–chemical conventional remediation techniques against advanced in situ and ex situ biotechnological approaches, including biochar assistance, microbial engineering, rhizosphere synergies, and engineered nanomaterials. By systematically linking industrial source dynamics with cellular toxicological mechanisms and field-scale engineering feasibility, this review establishes an actionable roadmap for future genetic, agronomic, and management interventions aimed at securing global food. Full article

Severe Cu and Pb enrichment in loess areas of northwestern China, mainly associated with mining and smelting activities, has increased the demand for efficient soil decontamination. Electrokinetic (EK) remediation is a promising in situ technology because it can drive ionic contaminants through low-permeability porous media with limited excavation and relatively low secondary disturbance. In this study, the effects of electric field strength, electrode type, and catholyte pH on Cu and Pb removal from contaminated loess were systematically evaluated using a large-scale EK reactor. The full name of EKG is electrokinetic geosynthetics. During treatment, pH, electrical conductivity, electric current, cumulative electroosmotic flow (EOF), and the spatial distributions of Cu and Pb were monitored. Increasing the electric field from 1.0 to 2.0 V cm⁻¹ increased current and EOF and accelerated anodic acid-front propagation, but it also strengthened cathodic alkalization and precipitation. Compared with graphite electrodes, electrokinetic geosynthetics (EKG) electrodes maintained higher current and EOF, generated stronger acidification, and increased Cu and Pb removal by approximately 25% and 5%, respectively. Among the tested catholyte conditions, pH 7.0 provided the best balance between electromigration and electroosmosis, achieving overall soil-phase removal efficiencies of approximately 19.0% for Cu and 8.0% for Pb. These results show that coordinated regulation of the electric field, electrode architecture, and electrolyte chemistry can mitigate the focusing effect in loess, although further enhancement is still required for field-scale decontamination. Full article

Heavy metal contamination of soils represents a persistent environmental challenge, for which in situ immobilization has emerged as a cost-effective and technically viable alternative to conventional invasive remediation technologies. This review comparatively evaluates three distinct categories of soil amendments—biochar, zeolite and attapulgite—within a unified analytical framework integrating extractable fractions (TCLP, DTPA, and CaCl₂) and geochemical fractionation approaches (BCR and Tessier). The novelty of this study lies in the systematic assessment of the dominant immobilization mechanisms associated with each amendment in relation to soil properties and the chemical speciation of the target metal, as well as in distinguishing between an apparent reduction in metal extractability and a genuine shift toward more stable geochemical fractions. The findings identify ion exchange as the primary immobilization mechanism in zeolites (NaA zeolite, 1–5% w/w, 96% reduction in TCLP-extractable Pb and 91% reduction in TCLP-extractable Cd), the synergistic action of adsorption, complexation, and precipitation in biochar systems (manure-derived biochar, 0–5% w/w, 97.4% reduction in the exchangeable Pb fraction according to the Tessier scheme), and the critical role of surface modification in attapulgite-based amendments (C-ATP, 4% w/w, 95.1% and 74.3% reductions in TCLP-extractable Pb and Cd, respectively). Because these efficiencies were obtained using different extraction protocols, they are not directly comparable. At the same time, cases of adverse responses were identified, including increased As extractability following the application of phosphate-modified biochar and the redistribution of Pb and Cd after amendment with natural zeolite in industrially contaminated soil. These observations highlight that amendment performance is not an intrinsic property of the material itself, but rather the outcome of specific geochemical interactions occurring within the soil system. Increased soil pH emerged as the principal common factor promoting metal stabilization across all amendment categories, whereas substantial variability in amendment dosage, incubation period, and analytical methodology limited direct quantitative comparisons among studies. Consequently, the selection of an appropriate soil amendment should be based on the integrated evaluation of soil physicochemical properties, contaminant speciation, and the intended scale of application, supported by long-term monitoring under field conditions. Full article

The contamination of aquatic environments by cadmium and other toxic heavy metals represents a major environmental concern requiring efficient and operationally sustainable remediation strategies. In this work, iron oxide materials were synthesized through a microwave-assisted hydrothermal method and evaluated for Cd(II) removal from aqueous systems. Different precursor compositions and organic additives were initially screened in order to identify the most suitable adsorbent formulation. The selected Fe-Tart material was characterized by FTIR, SEM-EDS, and XRD analyses, revealing hydroxylated and poorly crystalline iron oxide structures with heterogeneous surface organization. Batch adsorption experiments were performed under controlled conditions to investigate the influence of pH and equilibrium adsorption behavior, while adsorption data were analyzed using Langmuir and Freundlich isotherm models. Cd(II) uptake showed strong pH dependence, with adsorption progressively increasing from acidic to near-neutral conditions and reaching approximately 80% removal at pH 7–8. The Langmuir model provided the best fitting results (R² = 0.988), suggesting preferential occupation of energetically comparable surface sites with a maximum adsorption capacity of 6.51 mg g⁻¹. The adsorption behavior was interpreted within a pH-dependent surface complexation framework involving hydroxylated iron oxide surfaces. Although the adsorption capacity remained lower than that reported for some highly engineered adsorbents, the results indicate that microwave-assisted synthesis may provide a relatively simple and rapid route for preparing iron oxide-based materials potentially applicable to water remediation systems. Full article

Polymetallic mining severely disrupts farmland soil ecosystems, yet the vertical migration of heavy metals, interlayer pollution disparities between topsoil and deep soil, and quantitative source apportionment of composite pollutants remain poorly understood in mining–agricultural overlapping zones. Two core hypotheses were accordingly proposed: mining-derived heavy metals can migrate downward and accumulate in deep soil layers, and the coupling of geostatistical analysis and receptor modeling enables reliable differentiation between geogenic and anthropogenic pollution sources. To test these hypotheses, 512 topsoil and 148 deep soil samples were collected from the Fenghuang Mining Area for quantification of eight metals and metalloids (including As). Geostatistical approaches, the single pollution index (Pi), and Nemerow comprehensive pollution index (P_N) were utilized to characterize spatial heterogeneity and evaluate pollution severity, while a coupled PCA–PMF receptor model was adopted for quantitative source identification; vertical comparisons of element concentrations across soil profiles further validated the robustness of source apportionment outputs. The results revealed extensive heavy metal enrichment in both soil layers, with only topsoil Cd exceeding China’s risk screening value for agricultural land. Hg exhibited pronounced spatial variability and prominent anthropogenic fingerprints, and all target metals displayed consistent spatial distribution patterns along vertical soil profiles. Four distinct pollution sources were discriminated: geogenic sources dominating Cu, Zn, Cr, and Ni accumulation, mining-industrial emissions as the major contributor to Hg pollution, mixed industrial–agricultural inputs governing As and Pb enrichment, and traffic activities serving as the primary Cd source. Cd was identified as the priority pollutant threatening local farmland security. Confirmed downward percolation of anthropogenic metals creates persistent latent ecological risks across the study area, where mining and industrial discharges represent the dominant anthropogenic pollution inputs. This work systematically elucidates the geochemical signatures, vertical migration pathways, and quantitative source contributions of heavy metals in mining-disturbed farmlands, delivering solid scientific support for targeted source control, tiered risk management, and soil ecological remediation within the Fenghuang Mining Area. Moreover, the multi-method integrated analytical framework developed herein provides transferable guidance for heavy metal pollution mitigation in global polymetallic mining–agricultural regions with analogous geological and industrial backgrounds. Full article

Heavy metal-contaminated post-mining soils remain persistent sources of ecological degradation and contaminant dispersion. This study provides a quantitative field-based assessment of sorghum (Sorghum bicolor), maize (Zea mays) and soybean (Glycine max) cultivated on heavy metal-affected mining soil from the Jiu Valley, Romania, within a Living Lab platform. Soil properties, pseudo-total metal concentrations, multi-year biomass production, growth indicators, vegetation cover and aboveground plant metal concentrations were evaluated. The soils showed slightly acidic to near-neutral pH, low organic matter and multi-metal contamination, with Cr, Cu, Ni, Zn and Pb ranging from 82 to 146, 51 to 92, 41 to 79, 156 to 287 and 64 to 121 mg kg⁻¹, respectively. Total fresh biomass increased from 85 kg in the first cultivation year to 487 kg in the third cultivation year, with sorghum showing the highest final production (230 kg) and vegetation cover (55–86%). Aboveground Cr, Cu, Ni, Zn and Pb concentrations measured at species-specific levels of 6.21–8.06, 8.77–10.64, 7.48–12.92, 38.01–47.11 and 4.32–6.46 mg kg⁻¹ dry weight, respectively. Sorghum showed the highest preliminary phytomanagement suitability, mainly through stronger vegetation cover formation, higher fresh biomass production and lower visible stress under the investigated field conditions. Maize showed intermediate feasibility, whereas soybean appeared more sensitive to the degraded substrate. Biomass reuse should be considered only under controlled non-food pathways, such as pyrolysis or anaerobic digestion, and should only be considered after a dedicated assessment of dry biomass, conversion residues and metal fate. Full article

Heavy metal pollution poses a significant threat to industrial and agricultural ecosystems; however, thorough research on the coupled risks and migration mechanisms of heavy metals within soil-groundwater systems in arid-region industrial parks remains limited. This study systematically collected 312 surface soil samples and 239 groundwater samples from typical chemical industrial parks in Xinjiang, northwestern China. The pollution levels of six typical heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were quantitatively evaluated utilizing the Single Pollution Index (P_i), Nemerow Pollution Index (P_N), and Potential Ecological Risk Index (RI) for soil and the improved Heavy Metal Contamination Index (HCI) for groundwater. Additionally, GIS mapping and the Positive Matrix Factorization (PMF) model were integrated to delineate spatial distributions and primary emission sources. The assessment results indicated overall moderate pollution risks for Cd, Cu, and Ni in the soil, and for Cd, Pb, Cr, and Ni in the groundwater. Notably, Cd emerged as the primary risk contributor across both media. The RI identified Cd as the element posing the highest soil toxicity risk (with a mean RI of 53.57), while the HCI revealed that specific industrial zones face severe contamination levels (HCI > 4500), predominantly driven by Cd and Pb. GIS analysis illustrated a distinct distance–decay diffusion pattern emanating from industrial point sources. Crucially, PMF source apportionment demonstrated divergent contamination pathways: surface soil heavy metals (e.g., Cr, Cu, Pb, Zn) were primarily governed by top-down local industrial emissions (52.5%), whereas groundwater contamination was largely dictated by regional groundwater flow carrying mixed agricultural and natural geogenic inputs (75%). Furthermore, Pearson correlation analysis revealed a prevalent weak or negative correlation between heavy metal concentrations in the two media, suggesting a spatial “decoupling” of their contamination pathways. This phenomenon is likely driven by a dynamic “retention-leaching” mechanism within the arid vadose zone, where alkaline pH and high clay content act as a hydrochemical barrier impeding vertical migration. These findings underscore that soil and groundwater in arid industrial regions should be managed as distinct hydrochemical systems, providing a robust scientific basis for targeted remediation and the sustainable redevelopment of industrial brownfields. Full article

Lead (Pb) is a persistent and highly toxic heavy metal that poses significant ecological and human health risks due to its high bioaccumulation potential. In this study, nitrogen-doped biochar (NBC) was synthesized from straw-derived biochar via ball-milling and ammonium nitrate modification to remediate Pb-contaminated soil. Batch adsorption experiments demonstrated that the adsorption process was best described by the Langmuir isotherm model, indicating monolayer adsorption. X-ray photoelectron spectroscopy (XPS) revealed that Pb(II) immobilization by NBC occurred through multiple mechanisms, primarily precipitation and complexation with hydroxyl and pyrrolic-N functional groups. Subsequent pot experiments confirmed that NBC outperformed pristine biochar (BC) in reducing Pb bioavailability. This superior performance was attributed to the ability of NBC to increase soil pore water pH and significantly decrease soil redox potential (Eh). Moreover, compared to the control, a 5% NBC treatment (NBC2) significantly increased soil organic matter (SOM) by 136.24% while concurrently increasing soil available nitrogen (SAN), phosphorus (SAP), and potassium (SAK) by 46.91%, 75.72%, and 42.79%, respectively. Microbiological analyses indicated that NBC application enhanced soil alpha diversity (Chao1, ACE, and Shannon indices) and enriched beneficial bacterial phyla, such as Proteobacteria and Firmicutes. Random forest analysis identified the acid-soluble Pb fraction and SOM as the main drivers of bacterial operational taxonomic unit (OTU) composition. Specifically, NBC increased the relative abundance of the family Hungateiclostridiaceae, which may promote soil sulfide production and facilitate the precipitation of Pb into highly insoluble forms, further reducing its mobility and toxicity. Collectively, these findings demonstrate that NBC is a promising soil amendment that leverages both physicochemical and microbial pathways to immobilize Pb, mitigate environmental toxicity, and restore soil ecological health. Full article

Heavy metal (HM) contamination in urban soils is a pressing global issue, particularly in rapidly industrializing regions like Kazakhstan, where anthropogenic activities such as transportation, energy production, and manufacturing exacerbate accumulation in ecosystems. In Almaty, the largest city in Kazakhstan, urban expansion and legacy pollution pose risks to soil functions, biodiversity, and public health through bioaccumulation and migration pathways. This study evaluates the spatial distribution and ecological impacts of total heavy metal concentrations (HMs) (Pb, Cd, As, Zn, Cu, Ni, Co, Mo, Mn) in Almaty’s soils to inform remediation strategies. Soil samples (n = 73) were collected using a systematic grid sampling method across urban, industrial, and peri-urban zones in Almaty. HM concentrations were determined via X-ray fluorescence spectrometry (XRF) following GOST 33850-2016 standards. Pollution indices (contamination factor K_c and integrated pollution index Z_c) were calculated relative to Kazakhstani permissible limits (PDK RK) and Russian approximate permissible concentrations (ODK RF). Statistical analyses included Spearman’s correlation, boxplots, and coefficient of variation. Morphological, physicochemical (pH, humus content), and biological assessments evaluated degradation. Spatial interpolation via GIS mapped the hotspots. HM distributions showed significant variability, with As, Zn, and Ni exceeding norms in >90% of samples (median K_c ≈ 5 for As). Z_c classified >70% of sites as hazardous or extremely hazardous (Z_c > 32), with hotspots in central-eastern districts (Z_c 90–145). Strong correlations (ρ ≥ 0.6) identified a technogenic group (Pb–Zn–Cu–Ni) from traffic and industry, contrasting predominantly geogenic elements with possible anthropogenic contribution (As–Co–Mo–Mn). Pollution induced soil compaction, reduced humus/pH, and disrupting biogeochemical cycles. Local exceedances were noted near TECs, factories, and transport hubs. Almaty’s soils exhibit pervasive technogenic HM pollution, driven by urban sources, leading to ecosystem degradation and health risks. Future research should incorporate vertical profiling and isotopic sourcing for refined risk models. Prioritized monitoring and phytoremediation in hotspots are recommended to enhance resilience, aligning with UN SDGs for sustainable cities and ecosystems. Future research should incorporate vertical profiling and isotopic sourcing for refined risk models. Full article

Peripheral Artery Disease (PAD) is increasingly recognized as a complex environmental pathology driven by “contaminant metals,” rather than solely lifestyle factors. This scoping review (2016–2025) analyses the correlation between anthropogenic soil/water-derived Cadmium (Cd) and Lead (Pb) and progressive vascular hardening. The analysis confirms a robust, non-linear dose–response relationship. Chronic Cd exposure functions as a potent independent toxicant (Risk Ratio = 2.58 at 1 µg/L), significantly lowering Ankle–Brachial Index scores by inducing oxidative stress, inhibiting nitric oxide bioavailability, and displacing calcium in endothelial walls. Synergistically, Pb exposure, even at levels <5 µg/dL, compounds toxicity, amplifying arterial stiffness and hypertension. Consequently, “Heavy Metal Hardening” constitutes a critical link between water quality management and public health. Current regulatory thresholds appear insufficient to prevent chronic vascular remodeling, mandating urgent remediation of metal-laden aquifers and agricultural soils to mitigate this silent cardiovascular epidemic. Full article

Aquatic ecosystems are under severe stress from a diverse combination of contaminants, including heavy metals, pesticides, pharmaceuticals, and microplastics, driven by rapid industrialization, intensive agriculture, and urbanization. Globally, 80% of wastewater remains untreated, and conventional systems often fail to address emerging contaminants. Consequently, toxic heavy metals like lead and mercury can persist in water sources for decades. In response, phytoremediation has emerged as a scalable, eco-friendly, nature-based alternative. Among phytoremediation agents, duckweeds are increasingly recognized for their rapid growth, simple morphology, and continuous water-column contact. This review outlines the landscape of duckweed-based remediation, detailing molecular detoxification pathways and the synergistic role of associated microbiomes in enhancing environmental cleanup. Evidence indicates that contaminant removal is often supported by plant-microbe interactions. Despite extensive laboratory validation, field-scale implementation remains constrained by environmental complexity, pollutant mixtures, and variable climatic conditions. Furthermore, while duckweed systems hold promise within circular bioeconomy frameworks, converting wastewater into nutrient-rich biomass, contaminant accumulation in plant tissues raises concerns about biomass utilization and contaminant carryover. Addressing these challenges requires an integrative approach that links molecular detoxification, ecological interactions, and engineered system design to realize the full potential of duckweeds for sustainable aquatic pollution management. Full article

In the context of the circular bioeconomy and environmental protection trends, the efficient use of renewable resources has become a driving force for industry, and lignin represents precisely a renewable carbon resource, abundant in terrestrial biomass that could become a sustainable substitute for fossil resources, under conditions of full exploitation. This study systematically evaluates the biosorption of Manganese (Mn(II)) from aqueous media using unmodified Tripidium bengalense (Sarkanda grass) lignin. Under optimal operating conditions (adsorbent dosage of 5 g/L, pH 6.5, and 20 °C), a highly competitive experimental adsorption capacity of 12.52 mg/g was achieved. Kinetic studies revealed exceptionally rapid uptake rates, with thermodynamic equilibrium established within the first 30 min, fitting perfectly with the pseudo-second-order (Ho-McKay) model (R² ≥ 0.9998). Equilibrium data were best described by the Freundlich isotherm (R² ≥ 0.9886), confirming chemisorption via preferential inner-sphere complexation on a heterogeneous surface. Thermodynamic analysis verified that the process is spontaneous (ΔG ranging from −13.24 to −26.19 kJ/mol) and endothermic (ΔH from 11.21 to 14.83 kJ/mol). FTIR, SEM-EDX, and TG/DTG analyses confirmed successful Mn–O coordination involving phenolic hydroxyl and carboxylic groups. Furthermore, the lignin showed excellent recyclability, maintaining a retention efficiency over 70% (70.7–85.8%) after three desorption-resorption cycles using 1N HCl. Ecotoxicological validation via Sorghum bicolor L. germination tests confirmed the complete detoxification of the post-adsorption filtrates (up to 100% germination capacity), while the Mn(II)-loaded lignin completely suppressed seed germination (0%), proving secure metal immobilization. These findings establish raw Sarkanda grass lignin as an efficient, scalable, and ecologically sustainable biosorbent for heavy metal remediation. Full article