Search Results (1,498)

To assess the environmental impact of uranium mining operations in southern Kazakhstan, the elemental and radionuclide composition of soil samples collected from settlements in the Kyzylorda Region was investigated. The analysis was carried out using X-ray fluorescence (XRF) and gamma-ray spectrometry. Mean concentrations and variation ranges were determined for 28 chemical elements, including uranium, lead, antimony, and gamma-emitting radionuclides such as ¹³⁷Cs, ⁴⁰K, ²³²Th, ²³⁸U, ²²⁶Ra, ²¹⁰Pb, and ²⁴¹Am. The analysis of the specific activities of the artificial radionuclides¹³⁷Cs and²⁴¹Am was carried out in order to assess the influence of the Semipalatinsk Test Site on the soils of the study area. Based on the obtained data, heavy metal pollution indices, ecological risk indices, and radiological parameters were calculated to evaluate the potential environmental and human health impacts. Most elements were present at levels below average crustal abundances, suggesting limited anthropogenic influence. Slight exceedances for uranium, lead, and antimony are likely associated with regional geochemical features. Radiological assessment indicated that the radiation environment remains within internationally accepted limits. The lifetime cancer risk values for exposure of humans to natural radionuclides²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs from soil at 1 m above ground level ranged from0.19 × 10⁻³ to0.30 × 10⁻³, with an average of0.24 × 10⁻³. Nearly all sampling points remained below the risk threshold of 0.29 × 10⁻³, indicating minimal radiological hazard. The carcinogenic risk remained within the acceptable regulatory range for both adults (2.0 × 10⁻⁵) and children (4.4 × 10⁻⁵), whereas the non-carcinogenic hazard index for children (1.3) slightly exceeded the screening threshold of 1. This finding identifies children as the most sensitive receptor group under the conservative assumptions of the applied screening methodology. The study demonstrates the applicability of combined chemical and radiometric methods for comprehensive environmental assessments in uranium mining regions. The results are of interest both in terms of methodology and in understanding the local geochemical and radiological landscape. Full article

The growing volume of plastic waste produced has made the need for efficient identification and quantification strategies to detect and identify harmful contaminants, particularly heavy-metals, in industrial plastic-waste streams more urgent than ever. Traditional chemical digestion methods (acid digestion, ICP-MS, or AAS) provide accurate quantification and are time-consuming, costly, and not high-throughput-sorting. Laser-induced breakdown spectroscopy (LIBS) offers several advantages, including rapid real-time analysis, minimal sample preparation, multi-element detection, and efficient elemental characterization. The current review aims to investigate the possibility of using the LIBS technique to detect and quantify some heavy-metals like lead (Pb), cadmium (Cd), chromium (Cr), and arsenic (As) in heterogeneous industrial plastic wastes. The calibration strategies (reference standards) as well as optimization of the signal response and algorithms for data processing, including chemometric models, are evaluated to reduce the limit of detection and enhance analytical accuracy. The results indicate that LIBS can detect heavy-metal contamination at concentrations relevant to regulatory limits and can be scaled for online quality-control monitoring in plastic recycling facilities. In this review, the results have been summarized to support the use of LIBS for waste management towards environmental compliance, reduced use of hazardous materials in recycling products, and reduced health problems due to heavy-metal pollution. Full article

Heavy metal contamination poses significant ecological and public health concerns due to its persistence, toxicity, and bioaccumulative potential of toxic metals, threatening environmental quality and sustainable development. This study evaluated the distribution, pollution status, health risks, and sources of heavy metals in soils from industrial, agricultural, and residential areas of Rivers State, Nigeria, using Inductively Coupled Plasma–Mass Spectrometry (ICP-MS). Elevated concentrations of As, Mn, Se, Zn, and Co were detected across the study locations. Arsenic recorded the highest concentration in the Trans-Amadi industrial area (366.8 mg/kg), while Mn and Zn reached maximum concentrations of 1312 mg/kg and 327.9 mg/kg in Woji and Egi, respectively, exceeding the DPR limits for soil HMs. Pollution indices, including contamination factor, geo-accumulation index, enrichment factor, pollution load index, and Nemerow Integrated Pollution Index, revealed moderate to severe contamination, with the industrial zone exhibiting a NIPI value of 12.5. Health risk assessment identified ingestion as the dominant exposure pathway. Hazard quotient values for As (9.15) in the children category exceeded USEPA-acceptable limits, indicating potential non-carcinogenic risks. Carcinogenic risk assessment identified arsenic as the principal carcinogenic contaminant, with ingestion-derived Incremental Lifetime Cancer Risk (ILCR) values in the industrial area exceeding the USEPA maximum acceptable lifetime cancer risk threshold (1 × 10⁻⁴), particularly among children, whereas the carcinogenic risks associated with the other investigated metals generally remained within acceptable or tolerable limits. Source identification indicated that industrial emissions, vehicular activities, waste disposal, and agricultural practices were the primary contributors to heavy metal accumulation. These findings provide critical scientific evidence for targeted remediation, pollution prevention, and informed health-risk environmental management to protect soil quality, ecosystem integrity, and public health. The study supports evidence-based policies that advance sustainable land management, environmental protection, and progress in Rivers State, Nigeria. Full article

Cr(VI) pollution severely damages plant cell wall structure and membrane integrity. Proline-rich proteins (PRPs), key cell wall structural components, rely on proline as their biosynthetic precursor. Pro accumulation has been shown to positively correlate with PRP abundance, suggesting a direct biochemical link between exogenous Pro [Pro_(exo)] application and PRP-mediated cell wall function. However, how Pro_(exo) regulates PRP expression to maintain cell wall structural integrity and membrane stability in rice seedlings under Cr(VI) stress remains unclear. In this study, the subcellular distribution of Cr, electrolyte leakage (EL), cell wall thickness, and the expression of PRP genes in rice seedlings were evaluated. The results revealed that Cr(VI) stress induced significant increases in EL and changes in cell wall thickness in rice seedling cells (p < 0.05). The application of Pro_(exo) significantly mitigated EL and increased cell wall thickness (p < 0.05). Furthermore, Pro_(exo) markedly increased the sequestration of Cr within the seedling root cell walls while reducing its distribution in the cytoplasm and organelles of seedling shoot cells (p < 0.05). Phylogenetic analysis of 48 OsPRP genes, on the basis of their homology with seven functionally characterized PRPs from other species, revealed 12 candidate genes in rice potentially involved in the regulation of cell membrane stability, cell wall assembly, thickening, and integrity. Subsequent qRT-PCR analysis and gene expression variation factor calculation revealed that Pro_(exo) significantly promoted the expression of OsPRP1.1, OsPRP3, OsRePRP2.1, OsHyPRP18, and OsHyPRP27 in roots and that of OsHyPRP27 in the shoots of rice seedlings under Cr(VI) stress. These findings indicate that Pro_(exo) enhances Cr compartmentalization within the root cell wall and improves membrane stability, thereby contributing to Cr(VI) tolerance in plants through the modulation of these key PRP genes. Our findings provide novel insights into the mechanism by which Pro_(exo) regulates PRP expression to affect plant cellular structural stability and heavy metal tolerance. Full article

Coastal wetlands are important sinks for heavy metals, yet the linkage between vertical redistribution, quantitative source contributions, and ecological–health risk drivers remain insufficiently understood. This study collected the stratified sediment samples from three depth intervals (0–20, 20–40, and 40–60 cm) from 28 representative sites in the coastal wetlands of western Bohai Bay, and evaluated the spatial distribution, vertical variation, pollution status, potential sources, and ecological–human health risks of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb). The mean concentrations were below the Class I limits of the Marine Sediment Quality Standard. Most metals were close to or slightly below regional background values, whereas Cu and As showed mild enrichment and Cr was higher than values reported for Bohai Bay and Hangzhou Bay. Vertical profiles were generally homogeneous, with weak enrichment of specific metals, probably due to sediment resuspension, tidal disturbance, and bioturbation. Pollution assessment based on the geoaccumulation index (Igeo), Nemerow pollution index (P_N), and pollution load index (PLI) consistently indicated low contamination levels, with Hg and Pb as the main contributors to the regional pollution load. Source apportionment indicated that heavy metals were jointly influenced by lithogenic background (38.9%), atmospheric deposition (31.1%), and local anthropogenic activities (30.0%). Ecological risk assessment showed that the integrated risk index (RI) remained within the low-risk category, although Hg consistently fell within the moderate-risk range and Cd approached the moderate-risk threshold. Health risk assessment showed that both non-carcinogenic and carcinogenic risks were within acceptable limits for all receptor groups. Children had higher risks in core residential areas, whereas adults showed higher risks in non-core industrial–agricultural zones because of increased exposure frequency. The source–risk analysis indicates that non-carcinogenic risk is mainly associated with background-derived Cr, whereas carcinogenic risk is primarily linked to anthropogenic As inputs. These findings indicate that source contributions and risk contributions are not necessarily consistent, highlighting the need for source-oriented risk management in industrialized coastal wetlands. Full article

Background: Drilling slurry, a waste material generated during natural gas extraction, requires careful chemical characterization to determine its environmental hazard classification and inform appropriate management strategies. Methods: This study characterizes the drilling fluid used as raw material and the resulting drilling slurry waste, using a case study sample from the Buzău extraction area (Well 1 Florica, S.N.G.N. Romgaz S.A.), including total composition analysis, three-stage leaching tests, linear regression of leaching kinetics, and standardized geoaccumulation indices (Igeo, CF, PLI). Results: Total composition analysis confirmed low heavy metal concentrations (Cd = 0.02, Cr = 0.05, Pb = 0.64, Zn = 2.82 mg/kg dry matter). All leachate parameters remained below non-hazardous waste thresholds (Order No. 95/2005), with safety factors of 20–100× for regulated metals and 1.2–2.7× for chlorides, sulphates, and dissolved organic carbon. Standardized pollution indices confirmed Class 0 (unpolluted) status for all five metals, with a composite Pollution Load Index of 0.0124. Leaching regression analysis revealed dissolution-controlled release for chlorides, sulphates, and zinc (R² > 0.93) versus matrix-retention behavior for copper, nickel, cadmium, and chromium. Comparative analysis showed horizontal drilling generates approximately 146% more waste volume than conventional vertical drilling (170 m³ versus 69 m³ at 2100 m depth). Conclusions: The analyzed drilling slurry meets non-hazardous waste classification with substantial safety margins, corroborated by three independent analytical frameworks. Waste minimization strategies and biodegradable fluid substitution offer practical pathways to reduce the environmental footprint of natural gas drilling operations. Full article

To clarify the pollution characteristics and source composition of heavy metals in the paddy soils of the Yellow River irrigation district of Ningxia, a total of 515 surface soil samples were collected, and the concentrations of As, Hg, Pb, Cd, and Cr were measured. Regional-scale pollution assessment and source apportionment were conducted using the geo-accumulation index, spatial interpolation analysis, and the Positive matrix factorization (PMF) model. Based on the regional pollution assessment and spatial distribution patterns, a representative area with relatively elevated Cd accumulation and more pronounced anthropogenic influence was selected for local-scale isotope investigation. Eight paddy soil samples and potential end-member samples were collected, and, combined with literature-based end-member data, Pb and Cd isotopes were analyzed using the MixSIAR Bayesian (version 3.1.12) mixing model to further constrain the sources of Pb and Cd in village soils. The results showed that some sampling points in the study area exceeded the soil background values, but none of the points surpassed the screening values for agricultural soil pollution risk, indicating that the overall risk of paddy soils in the study area remained low. Geo-accumulation index results indicated that As, Pb, and Cr were predominantly classified as unpolluted, whereas Hg and Cd showed more pronounced accumulation, with most sampling points reaching unpolluted to moderately polluted or higher. PMF results revealed that heavy metals in the study area primarily originated from natural sources, agricultural activities, coal combustion-related sources, and industrial–traffic mixed sources. Cd was mainly influenced by agricultural sources, Hg was primarily affected by coal combustion and related industrial activities, and Pb exhibited a mixture of multiple sources. Local isotope analysis in the representative area further indicated that industrial and agricultural sources were the main contributors to soil Cd, accounting for 34.3% and 33.1%, respectively. Pb was primarily derived from agricultural activities (38.1%), while coal emissions, industrial sources, natural sources, and traffic contributed 19.2%, 18.3%, 16.9%, and 7.5%, respectively, indicating a complex mixture of agricultural, industrial, coal-combustion, natural, and traffic-related inputs. The combined application of PMF and Pb/Cd isotopes allowed for constraints on heavy metal sources at both regional and local scales, providing a scientific basis for pollution control and agricultural safety management in paddy soils of the Yellow River irrigation district. Full article

The Laspias River and Lissos River sustain the hydrological and ecological functioning of the Vistonida Lake wetland complex, a protected Natura 2000 site and Ramsar Convention Wetland of International Importance, by regulating nutrient transport and supporting aquatic biodiversity. Thus, the water quality of the rivers Laspias and Lissos and their adjacent coastal zones located in the prefectures of Xanthi and Rhodope (NE Greece) respectively was monitored regarding key metal concentrations for a period of two years. The monitoring of these watersheds and coastal zones was based on seven sampling stations in the Laspias River, twelve stations in the Lissos River and four stations in each river’s coastal zone. During water monitoring of both rivers, a wide range of chemical elements was analyzed to assess water quality. In the present work, the heavy metal pollution index (HPI) and the heavy metal evaluation index (HEI) were assessed in both rivers and their coastal area for four successive seasons. The mean HPI and HEI values for the Laspias River were 54.66 ± 10.82 and 1.45 ± 0.22, whereas the respective indices in the Lissos River were 14.43 ± 4.14 and 0.39 ± 0.14. The mean HPI and HEI values for the adjacent coastal zones of the Laspias and Lissos Rivers were 7.42 ± 1.52 and 0.14 ± 0.05, as well as 10.39 ± 0.83 and 0.23 ± 0.02, respectively. Therefore, the average HPI values for both rivers and their coastal zones were below the proposed threshold (<100), while the HEI of the Laspias River classified the water quality in the second category (slightly affected, HEI from 1.0 to 2.0 due to the effect of Mn) and the Lissos River in the first category (very pure/pure, HEI < 1), respectively, considering drinking water thresholds. The HEI indices of their coastal zones characterized the water quality as very pure/pure. Full article

Accurate source identification is essential for the prevention and control of heavy metal(loid)s (HMs) contamination in farmland soils. Conventional source-apportionment approaches often rely on limited indicators and expert judgment, which can increase uncertainty in source interpretation. In this study, 800 topsoil samples collected from farmland in Ningxia, together with 24 environmental and anthropogenic variables, were used to develop element-specific machine learning models for Cd, Cr, Hg, Pb, and As. Five algorithms, including random forest (RF), Extra Trees (ET), extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), and least absolute shrinkage and selection operator (LASSO-stacking), were compared, and Shapley additive explanations (SHAP) were used to interpret the variables statistically associated with the spatial variability of each metal. Positive matrix factorization (PMF) was further applied to identify potential source categories. Model performance varied among metals, indicating element-specific differences in predictability and controlling factors. SHAP analysis showed that precipitation, temperature, spatial coordinates (longitude/latitude), cropping intensity, and industrial-source fine particulate matter emissions were among the most important associated factors, although their relative importance differed across elements. PMF results suggested that 73.8% of Cd was associated with agricultural inputs, 87.6% of Hg with industrial atmospheric deposition, and 68.4% of Cr and 46.7% of As with natural sources, Pb showed relatively weak predictability, suggesting that its spatial variability may be influenced by unmeasured local or legacy inputs, while model-derived associations indicated possible links with spatial gradients, terrain-hydrological conditions, wind-related variables, and soil carrier properties. Overall, this study presents an integrated framework that combines machine learning-based associated-factor analysis with receptor-model source apportionment, providing a more nuanced understanding of HMs contamination in farmland soils and supporting targeted soil pollution prevention and control. Full article

This study investigated the effects of urbanization on zooplankton communities in the Nanming River, a typical karst urban river in Southwest China. Thirty-three sampling sites were set along an urbanization gradient: urban, suburban, and exurban areas. We identified 33 zooplankton species, with rotifers dominating (84.62%). Zooplankton abundance and diversity were significantly higher in the exurban area, showing a negative correlation with urbanization intensity. Lepadella ovalis and Monostyla angulata were dominant, while Lecane cornuta was exclusive to the exurban zone. Gradient Boosting Models (GBMs) and Structural Equation Modeling (SEM) indicated that Cu, Zn, TN, and NH3-N were key drivers, and urbanization acted via heavy metal pollution and nutrient regulation. Rotifers showed strong urbanization adaptability, while copepods were most sensitive. Controlling nitrogen and heavy metals is critical for protecting karst urban river ecosystems. Full article

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

Heavy metal pollution has become a major environmental challenge limiting agricultural productivity worldwide. Copper (Cu), although an essential micronutrient, becomes phytotoxic at elevated concentrations, primarily by inducing oxidative stress. Among the most widespread metabolic adjustments triggered by abiotic stress is the accumulation of proline, which is a compatible osmolyte that stabilizes proteins and membranes and helps maintain cellular redox homeostasis. This paper demonstrates that the heterologous expression of TsPAP1, a triticale gene encoding a prolyl aminopeptidase, enhances proline accumulation and confers increased Cu tolerance in Arabidopsis thaliana. Under Cu stress, transgenic lines maintained superior physiological performance relative to the wild type (WT), as evidenced by the reduced biomass loss and lower accumulation of malondialdehyde and reactive oxygen species. Cu exposure activated antioxidant defenses; however, the induction of catalase (CAT), class III peroxidases (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) activities was more pronounced in transgenic lines. Transcriptomic analysis revealed a higher expression of genes encoding antioxidant isoforms localized to chloroplasts (sAPX, CSD2), the cytosol (APX1), peroxisomes (CAT1), and the apoplast (Prx02, Prx51), indicating targeted reinforcement of the multi-compartmental redox defense system. Together, these findings identify TsPAP1 as a potential regulator of proline-dependent redox homeostasis that contributes to enhanced Cu tolerance through the coordinated activation of antioxidant networks. The results further suggest that PAP-dependent peptide turnover contributes to proline-mediated stress adaptation, linking peptide metabolism with antioxidant regulation and highlighting TsPAP1 as a promising target for engineering heavy metal-resilient crops. Full article

This study advances sustainable wastewater management by investigating the efficacy of untreated pine cone powder (PCP), an abundant and renewable forest byproduct, for Fe^II removal from aqueous solutions. The surface morphology and composition of PCP was characterized by performing SEM-EDX, FTIR, point of zero charge, and total specific surface area analysis. Investigation of experimental factors revealed that equilibrium adsorption capacity increases with higher pH and temperature but decreases with elevated initial Fe^II concentration and ionic strength. The experimental kinetic and equilibrium data were best fitted to the pseudo first-order and Freundlich models, respectively. Thermodynamic analysis further indicated that the adsorption process was spontaneous and endothermic in nature, accompanied by an increase of randomness at the solid–liquid interface. Low activation and Temkin bonding energies suggest that physical adsorption is the dominant removal mechanism. With a maximum Langmuir adsorption capacity of 12.7 mg g⁻¹, PCP represents a promising eco-friendly adsorbent for the removal of Fe^II. By transitioning from conventional, high-footprint water treatments to such low-impact, eco-friendly alternatives, this research supports the circular valorization of biomass as a viable solution for the sustainable mitigation of industrial heavy metal pollution. Full article

Groundwater is vital to subsurface ecosystems and to maintaining water supplies for human and environmental needs. Heavy metal pollution of water bodies poses a significant threat to environmental health and human well-being. In this paper, a detailed spatiotemporal analysis of heavy metal pollution at a network of 35 sampling sites is presented for the summer, autumn, and winter seasons. The water samples were analyzed based on the concentration (μg/L) of eight priority metals, such as Lead (Pb), Mercury (Hg), Cadmium (Cd), Arsenic (As), Chromium VI (Cr-VI), Copper (Cu), Zinc (Zn), as well as Iron (Fe). Measuring contamination levels, identifying space hotspots, and explaining seasonal variations were the key tasks. The results show that Fe, Zn, and Cu concentrations are consistently high across seasons, with mean values ranging from 234.3 to 253.2 µg/L (Fe), 163.2 to 175.6 µg/L (Zn), and 107.0 to 109.2 µg/L (Cu), indicating a widespread geogenic or diffuse source. The most significant seasonal deviation was observed in the fall when there were unusually high levels of Cd and Hg, with mean concentrations reaching 0.476 µg/L and 0.312 µg/L, respectively, suggesting a strong seasonal contamination event or mobilization process. The spatial analysis showed that the locations (e.g., L6, L8, L10, L28, L29) exhibited common hotspots for different metals, with maximum concentrations reaching up to 793.3 µg/L (Fe), 602.3 µg/L (Zn), and 508 µg/L (Cu). Principal Component Analysis (PCA) effectively separated seasonal trends and classified metals into anthropogenic (Pb, Cd, Hg, Cr (VI)) and geogenic/diffuse (Fe, Zn, Cu) groups. The health risk assessment indicated no significant non-carcinogenic risk, although children are more vulnerable, while arsenic levels in winter approached the upper acceptable carcinogenic limit (up to 1.1 × 10⁻⁴). Overall, the study highlights the importance of multi-seasonal monitoring by capturing temporally abrupt contamination events and provides a novel integrated framework that combines seasonal analysis, spatial hotspot identification, and multivariate techniques, distinguishing it from conventional single-season or non-integrated studies. Full article

Water resources are essential for human well-being. However, water pollution is a major global problem with significant implications for the environment and public health. To address these challenges, this study presents an integrated perspective on water pollution by correlating pollution sources, transport pathways, exposure routes, and associated risks to human health. The methodology combined a systematic review conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines with a bibliometric analysis performed by using VOSviewer version 1.6.19, a software tool for constructing and visualizing bibliometric networks. A total of 332 publications published between 2015 and 2025 were retrieved from the Scopus and Google Scholar databases and met the PRISMA eligibility criteria. The findings indicate that both natural and anthropogenic sources contribute to water contamination, introducing pollutants such as heavy metals, pesticides, pharmaceutical residues, microplastics, and pathogenic microorganisms with potential human health impacts. Bibliometric analysis revealed a transition from conventional water quality assessments toward integrated approaches emphasizing health risks and environmental interactions. The study further identified important knowledge gaps regarding contaminant mixture effects and synergistic toxicity, which remain insufficiently addressed in current scientific and regulatory frameworks. These findings highlight the need for strengthened regulatory strategies, advanced treatment technologies, and evidence-based water governance to support environmental sustainability and public health protection. Full article