Search Results (1,067)

The co-contamination of manganese ions (Mn²⁺) and ammonia nitrogen (NH₄⁺) caused by the stockpiling of manganese residue poses a serious threat to the ecological environment. In this study, a series of the composite was prepared from red mud, bentonite, and corn straw via oxygen-limited pyrolysis. The effects of pyrolysis temperature and raw material ratio on the material properties were investigated, and the synergistic remediation performance of the composites for Mn²⁺ and NH₄⁺ in manganese residue-contaminated soil was evaluated through a 180-day soil column experiment. The results showed that the composite prepared with a raw material ratio of 1:1:1 at a pyrolysis temperature of 700 °C exhibited the largest specific surface area and the most developed pore structure, achieving a Mn²⁺ removal rate of 92.72% ± 0.85% in aqueous solution. In the soil column experiment, the material prepared at 700 °C gave the highest immobilization rate for soil Mn²⁺ (96.22% ± 0.5%), whereas the combined addition of materials prepared at 700 °C and 500 °C achieved the best removal efficiency for NH₄⁺ (99.33% ± 0.23%). Mechanistic studies revealed that the stabilization of Mn²⁺ is primarily attributable to alkaline precipitation and mineral lattice solid solution induced by the composite, leading to the formation of stable spinel phases (e.g., (Fe,Mn)₃O₄) and insoluble manganese phosphate-carbonate salts. The removal of NH₄⁺ is proposed to proceed via adsorptive enrichment by the porous structure and Fe⁰-mediated Fenton-like catalytic oxidation, ultimately converting NH₄⁺ to N₂ gas. The 180-day monitoring results demonstrated that the remediation effect continuously increased over time, indicating good long-term stability of the composite. This study provides an efficient, low-cost functional material derived from solid waste for the remediation of manganese residue-contaminated soil and offers a theoretical basis for the synergistic resource utilization of multiple solid wastes. Full article

Soil contamination with heavy metals (including Cu, Zn, Cd, and Pb), alongside climate change, represents a key challenge for the sustainability of forest ecosystems. Sycamore maple (Acer pseudoplatanus L.), as a pioneer species with high phytostabilization potential, can play a significant role in ensuring forest persistence in areas affected by industrial emissions. In this context, the abundance of natural sycamore maple regeneration was determined along a transect originating at the “Gilów” Extractive Waste Treatment Facility in Poland. On 13 research plots arranged along the transect, the share of sycamore maples was assessed within height classes of up to 0.5 m, 0.5–1.5 m, and above 1.5 m. Furthermore, the soil content of Cu, Zn, Mn, Fe, Pb, Cd, Ni, and Cr, among others, was determined for each plot. The results showed a statistically significant positive correlation between Acer pseudoplatanus regeneration and the soil content of iron and nickel, as well as a statistically significant negative correlation with lead content. The results concerning nickel suggest that low concentrations of this element may stimulate the natural regeneration of sycamore maple. Full article

Human health risk assessment of vapor intrusion caused by organic pollutants is commonly based on steady-state predictions of partition and vapor migration in the subsoil. This study develops a pseudo-dynamic, process-based Partition–Diffusion Risk Model (PDRM) using a one-dimensional numerical model for organic mixtures to assess the time evolution of cancer and non-cancer risks, indoor air concentrations, and non-aqueous phase liquid (NAPL) formation. The model has been applied to a low-carbon sandy soil without microbial degradation, which might be a worst-case scenario. Six simulation scenarios combined two source concentrations (1000 and 3000 mg/kg) and three source depths (1, 3, and 5 m) over 30 years. Results show that source depth governs exposure dynamics: shallow contamination poses unacceptable risks rapidly but declines quickly, whereas at greater depths, unacceptable levels appear later and persist throughout the exposure period. NAPL formation may act as a secondary source, sustaining vapor release and extending indoor exposure under high-loading conditions. Multicomponent partitioning induces nonlinear, compound-specific behavior, with the first 3–5 years representing a critical period for rapid risk changes. Conventional models show that neglecting NAPL formation and time variability may lead to an underestimation of cancer risk by up to an order of magnitude. These findings highlight the importance of incorporating depth and time-dependent characterization to reduce uncertainty in vapor intrusion risk assessments. Full article

Cadmium (Cd) contamination in soil poses a serious threat to crop quality. Biochar is widely regarded as an effective amendment that can reduce Cd bioavailability and limit Cd uptake by crops. However, studies on the rapid and nondestructive evaluation of crop physiological responses under biochar-mediated alleviation of Cd stress remain insufficient. Spectral modeling methods can enable rapid and nondestructive monitoring of crop physiological status. In this preliminary experiment, Zhengdan 958 maize seedlings grown in Cd-contaminated soil were subjected to five biochar application rates: 0, 10, 30, 50, and 70 g/pot, designated as CK, A1, A3, A5, and A7, respectively. The study established a non-destructive spectral detection model for relative chlorophyll content expressed as SPAD values of maize leaves to achieve spectral inversion of leaf physiological information. The alleviating effect of biochar on Cd stress was evaluated by analyzing SPAD values and Cd accumulation in roots, stems, and leaves. The original spectral data underwent preprocessing steps including multivariate scattering correction, standard normal variable transformation, normalization, trend removal, first-order derivative transformation, and second-order derivative transformation. The effectiveness of different preprocessing methods was compared using partial least squares regression. Feature bands were identified via Pearson correlation analysis, and support vector regression models were established based on genetic algorithm (GA), particle swarm optimization (PSO), and grid search optimization. The results demonstrated that biochar application significantly increased the SPAD values of corn leaves (r = 0.879) and reduced the proportion of bioavailable Cd in soil, with the A7 treatment showing the most substantial decrease (30%). This indicates that biochar effectively mitigates Cd’s inhibitory effect on chlorophyll synthesis, with the alleviation effect enhancing as biochar application rates increased. Validation of the partial least squares regression model revealed that detrended spectra achieved optimal predictive performance (R²c = 0.94, RMSEC = 0.82, R²p = 0.88, RMSEP = 1.15), leading to the development of three optimized support vector regression models: GA-SVR, PSO-SVR, and GS-SVR. The GA-SVR model with a sigmoid kernel demonstrated the best internal validation performance for predicting SPAD values in maize leaves (R²c = 0.95, RMSEC = 0.24; R²p = 0.75, RMSEP = 1.63). This study provides preliminary theoretical support and technical reference for rapid spectral detection of the physiological status of maize under biochar-mediated mitigation of cadmium stress. Full article

Reprocessing historical lead–zinc (Pb–Zn) slag offers a circular-economy pathway for secondary metal recovery, yet it can remobilize legacy contaminants where containment is inadequate, transferring risk to the surrounding land. Sustainable management of such sites requires frameworks that link contamination assessment to actionable remediation. We integrated ICP-OES geochemistry, native-plant biomonitoring, and US EPA RAGS-based risk modeling at an active Pb–Zn slag reprocessing site in Shymkent, Southern Kazakhstan. Twenty-four soil samples along four cardinal transects, two reference samples, and four composite plant samples (Centaurea pseudosquarrosa + Plantago lanceolata) were analyzed for ten metals by ICP-OES. UCC-referenced indices classified six metals as geoaccumulation Class 6 at most points (enrichment factors up to 90,871, confirming an exclusively anthropogenic origin). Peak concentrations reached 9350 mg·kg⁻¹ Pb, 290 mg·kg⁻¹ Cd, and 10,900 mg·kg⁻¹ As—exceeding Kazakhstan MPC by 72×, 290×, and 5450×. Worst-case carcinogenic risk reached 4.3 × 10⁻³ (43× above the US EPA threshold), driven almost entirely by arsenic (93%); ecosystem risk (RCR_total = 223) was dominated by cadmium (43%), arsenic (27%), and mercury (16%)—a disconnect between mass-based and toxicity-based prioritization. On this basis we propose a three-tier remediation framework (engineered containment, phytostabilization, monitored attenuation) that couples resource recovery with contamination control, is transferable to analogous Pb–Zn legacy sites, and supports sustainable land use, urban resilience, and responsible secondary-resource use. Full article

Rice, a staple food for over half of the global population, faces significant threats from environmental stressors such as heavy metal (HMs) contamination, notably cadmium (Cd) and arsenic (As), and increasing drought severity, exacerbated by climate change. These challenges not only compromise rice yield and quality but also pose serious food safety risks due to HM accumulation in grains, endangering human health. Modified biochar (MBC), a carbon-rich material derived from the pyrolysis of organic matter with post-treatment enhancements, has emerged as a strategy to address these dual stressors. MBC application (typically 5–20 t ha⁻¹) reduces Cd and As bioavailability in paddy soils by 40–60% and decreases metal accumulation in rice grains by 20–85% compared to the control. Under drought conditions, MBC improves soil water-holding capacity by 11–45% and enhances crop water use efficiency by 15–24%, leading to yield improvements of 20–50% under moderate water deficit. Furthermore, MBC supports nutrient availability, fosters robust root systems, and enhances soil aeration, collectively improving rice growth under adverse conditions. Beyond its agronomic benefits, MBC provides a framework for addressing multiple challenges by integrating scientific innovation, policy alignment, and community participation. This approach not only reduces heavy metal toxicity and strengthens plant resilience but also enhances food security and advances Sustainable Development Goals (SDGs 2, 3, 4, 12, 13, 15, 17). By promoting environmentally sustainable agriculture and contributing to climate change mitigation, MBC represents a transformative tool for ensuring sustainable rice production in the face of global challenges. 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

Mercury (Hg) is a global pollutant that poses a serious threat to ecosystems and human health. Biochar has shown great potential for mercury removal due to its porous structure and abundant surface functional groups. However, redox-active moieties on biochar can reduce adsorbed Hg²⁺ to volatile Hg⁰, leading to secondary mercury dispersion. To suppress this reduction, this study proposes a strategy of co-pyrolyzing coal gangue with rice husk to prepare composite biochars (RHB/CG), leveraging the abundant metal oxides in coal gangue to tailor the surface chemistry of biochar. The materials were characterized by FTIR, Raman, and XRD; static adsorption, mercury speciation analysis, and kinetic experiments were conducted. The results show that coal gangue incorporation significantly enhances the Hg²⁺ adsorption capacity of biochar, with the equilibrium adsorption capacity calculated by the pseudo-second-order kinetic model, increasing from 20.6 mg/g for pristine RHB to 38.7 mg/g for RHB/CG-1:1. More importantly, RHB/CG composites effectively suppress the reduction of Hg²⁺ to Hg⁰, and the amount of Hg⁰ accumulated in the system is 57.1% lower than that of pristine RHB. Mechanistic studies reveal that coal-gangue-derived basic functional groups (e.g., C–O–C, Si–O–M) inhibit reduction via sequestering Hg²⁺ through coordination and disruption of electron transfer pathways. PHREEQC simulations (pe = 6.0) confirm the decreased tendency of Hg²⁺ reduction to Hg⁰ with increasing pH, in good agreement with the experimental results showing reduced Hg²⁺ reduction. The corresponding results provide a green and sustainable solution for mercury-contaminated water and soil remediation. Full article

Arsenic (As) and lead (Pb) contamination of soils surrounding abandoned mines threatens environmental safety and limits their potential for agricultural reuse. Although calcium-based materials are widely used for heavy metal stabilization, integrated assessments of shell-based stabilizers considering both contaminant immobilization and soil functionality remain limited. This study assessed the effectiveness of shell-based stabilizers derived from fishery by-products, namely cockle and manila clam shells, which are primarily composed of calcium carbonate (CaCO₃), and their influence on soil health and crop safety. The shells were processed into natural and calcined forms and applied to As- and Pb-contaminated soils. Stabilization was evaluated using extraction tests, soil health indicators, and a lettuce cultivation experiment. The natural and calcined shell treatments reduced the extractable concentrations of As and Pb. Calcined shells exhibited higher immobilization efficiency due to Ca–As precipitation and the formation of calcium silicate hydrate and calcium aluminate hydrate phases. However, these treatments induced excessive alkalinity, negatively affecting soil chemical properties and overall soil functionality. In contrast, natural shell treatments provided a more balanced performance by reducing heavy metal mobility while maintaining favorable soil conditions. Lettuce grown under the stabilization–cover soil system showed at least an 87.4% reduction in As concentration compared with the control, while Pb was not detected in any stabilization-cover soil treatment. These results highlight the importance of evaluating shell-based stabilizers within an integrated framework that considers both contaminant immobilization and soil health. Full article

Soil contamination by heavy metals (HMs) [or potential toxic elements (PTEs)] poses serious risks to ecosystems and human health. Metals persist in the environment and can reach groundwater and freshwater as part of the food-chain. In soils, anthropogenic inputs dominate over geogenic sources. Metal mobility is strongly controlled by factors such as pH, mineralogy, and erosion processes that transport metal-bearing clay fractions. Wind and water can transport soil, mainly clay particles that can usually bind contaminants such as HMs. Using waste material is a tool suggested from the circular economy, so waste becomes a valuable resource. This study evaluates the immobilization efficiency of several heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) using phosphate amendments—synthetic hydroxyapatite, phosphatic rock from Florida and Morocco—applied to a brownfield site. Heavy metal immobilization followed a two-step mechanism: first rapid surface complexation and secondly partial dissolution of hydroxyapatite and ion exchange with Ca, leading to the precipitation of metal-substituted hydroxyapatite phases. Synthetic hydroxyapatite generally shows the best efficiency, whereas phosphatic rocks were less effective but still provided a measurable immobilization. From a circular economy perspective, however, phosphatic rocks remain attractive due to their lower cost, availability, and waste-valorization potential. Full article

Soil vulnerability is commonly assessed using environmental indicators; however, the lack of systematic and continuous monitoring often leads to incomplete and fragmented data, particularly in surface coal mining areas affected by potentially toxic element (PTE) contamination. Existing studies mainly focus on impact assessment, with limited emphasis on structured decision-support frameworks for selecting optimal soil protection strategies. This study addresses this gap by proposing an integrated hybrid decision-making framework that combines the Analytic Hierarchy Process (AHP), Sustainability Balanced Scorecard (SBSC), and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The main contribution lies in integrating strategic sustainability perspectives (SBSC) with quantitative multi-criteria methods (AHP and TOPSIS), enabling a transparent and consistent evaluation of soil protection strategies across environmental, economic, technical, and social dimensions. The framework was applied to the Kostolac mining and energy complex in Serbia as a representative case study, using data from the State of the Environment Report as the basis for expert evaluation. The results identify risk reduction and environmental effectiveness as the dominant criteria, while the Progressive Strategy (SBSC) achieved the highest ranking. Sensitivity analysis confirmed the robustness of the model. From a policy perspective, the findings support prioritizing sustainability-oriented and risk-reduction strategies in mining regulations and investment planning. Full article

Potentially toxic elements (PTE) pollution from lead–zinc (Pb–Zn) production poses significant ecological risks, requiring systematic assessment across the industrial chain. This study investigated soil, surface water, and sediments near a Pb–Zn mining area, integrating pollution indices (I_geo, NIPI, RI) with human health risk models. A spatial analysis framework was established by combining proportional symbol mapping and Thiessen polygons to analyze contamination patterns under small-sample conditions. Results showed a clear pollution hierarchy: smelting > beneficiation > tailings ≈ mining. Smelting and beneficiation zones exhibited multi-element pollution; Hazard Index (HI) exceedance probabilities reached 89% and 95%, respectively, while carcinogenic risk (CR) exceedance approached 100% across all zones. Cd was the dominant ecological risk factor, particularly in mining and tailings zones, where risk was mainly driven by a single element. Source apportionment identified two industrial groups—smelting-related (Pb, Hg, Zn, Se) and ore-associated (As, Cd, Cu, Sb)—whereas Cr, Ni, Co, and V were mainly derived from natural sources. These results indicate the need for coordinated management of beneficiation and smelting processes and provide a spatial analysis approach for small-sample assessment. Full article

To investigate the contamination status, sources, spatial distribution, and health risks of heavy metals in paddy soils of Hexian County, 63 surface soil samples were analyzed for eight metals. Multiple pollution indices and multivariate statistical methods were applied to evaluate contamination levels and identify potential sources. Source apportionment was conducted using principal component analysis (PCA) combined with correlation analysis and spatial distribution characteristics. Results showed variable concentrations of heavy metals, with arsenic, copper, and lead exhibiting relatively higher single-factor pollution indices. The Nemerow pollution index (PN) ranged from 0.86 to 3.05 (mean = 1.16), indicating overall slight to moderate pollution, with localized areas showing higher pollution levels. The potential ecological risk index (RI) ranged from 28.06 to 66.45 (mean = 35.66), which was well below the threshold of 150, indicating a low ecological risk. Health risk assessment indicated negligible non-carcinogenic risks for both children and adults. Although carcinogenic risks remained within acceptable limits, children exhibited higher susceptibility, suggesting potential long-term concerns. Overall, these findings provide scientific evidence for targeted pollution control and risk-based agricultural management in Hexian County, and offer practical implications for mitigating heavy metal contamination and protecting agricultural sustainability in regions along the lower Yangtze River. Full article