Environmental Geochemistry and Health最新文献

The multifaceted utility of biochar in environmental applications stems from its porous structure, ample surface area, and rich oxygen-containing functional groups. However, interactions between biochar and its surroundings can lead to the release of potentially harmful components, necessitating a comprehensive understanding of environmental impacts. This review categorizes adverse biochar effects on their detrimental components, surface attributes, structure, and size, delving on water, soil, plants, animals and atmospheric ecosystems. It also presents different methodologies for detecting environmental risks associated with biochar application, offering guidance for future toxicity assessment and avoidance strategies. Biochar created via high-temperature pyrolysis under limited oxygen can harbor various known contaminants and emerging threats (persistent free radicals and metal cyanides), posing risks like phytotoxicity, cytotoxicity and neurotoxicity. The ecotoxic potential of biochar concerning specific contaminants, comprehensive strategies to mitigate this entire spectrum of contaminants within biochar are lacking. This review comprehensively explores the formation mechanisms of these contaminants and their potential risks to ecosystems and underscores the need for effective contamination control strategies during biochar production. It emphasizes the significance of designing pyrolysis units that ensure separation of pyrolysis liquids from solids, minimizing organic contaminant condensation onto biochar. Reducing total levels of PTE holds promise through strategies such as co-pyrolysis of biomass containing both metal-rich and metal-free components, complemented by the inherent decrease in PTE levels with higher pyrolysis temperatures. With these recommended strategies, there is potential to produce biochar posing minimal environmental risks, empowering sustainable applications in diverse environmental contexts.

In this study, the spatiotemporal distributions, influencing factors, sources, and ecological risks of atmospheric microplastic deposition in a valley city from 2019 to 2023 were investigated. On average, dry deposition accounted for 75.90% of the microplastic deposition. The deposition fluxes exhibited significant spatiotemporal differences. The deposition fluxes in summer and winter were the highest (814.36 p m^-2 d^-1, on average) and lowest (178.65 p m^-2 d^-1, on average), respectively. The average annual and seasonal deposition fluxes were strongly influenced by the precipitation intensity and frequency, the frequency of daily average wind speeds ≥ 2 m s^-1, the boundary layer height, the air temperature and the ultraviolet radiation dose. In addition, the average annual deposition fluxes were strongly influenced by the inner city travel intensity and number of tourists, and the average seasonal deposition fluxes were strongly influenced by the seasonal precipitation amount. The spatial distributions of deposition fluxes were influenced by population density. Approximately 42.11% of the microplastic deposition originated from local sources, and the nonlocal sources were mainly from the northwestern region of the study area. The pollution level, hazard level and ecological risk of microplastic deposition during the pandemic period were lower than those during the non-pandemic period. Our results suggested that atmospheric microplastic deposition was influenced by both natural and anthropogenic factors.

Dense non-aqueous phase liquids (DNAPLs) are pervasive pollutants in groundwater systems and exhibit complex migration behavior and phase transitions. The presence of residual-phase DNAPLs often leads to persistent concentration tailing and rebound effects, which significantly hinder effective remediation. The efficacy of surfactant-enhanced aquifer remediation (SEAR) in removing residual-phase DNAPLs is hampered by a complex interplay of influencing factors. This review systematically analyzes DNAPL migration and retention, identifying the residual phase as the critical barrier to successful remediation. SEAR performance depends critically on surfactant properties, aquifer media, and hydrodynamic conditions, leading to variable outcomes. A comprehensive analysis of residual phase DNAPL migration mechanisms reveals that DNAPL movement is predominantly controlled by the interplay of gravitational, capillary, and viscous forces. This paper presents a force-balance analytical framework connecting DNAPL displacement to key remediation parameters. Remediation success relies on identifying and regulating dominant forces under site-specific conditions, while aquifer heterogeneity and coupled parameters add complexity in three-dimensional field settings. Thus, multi-parameter interactions need systematic evaluation. Large-scale research on multi-parameter coupling mechanisms is currently lacking, and future efforts should address this to advance precise DNAPL remediation strategies.

The impacts of toxic elements (TEs) have been widely assessed in artisanal gold (Au) mines in the Amazon, but few investigations have focused on adjacent soils affected by this activity. These soils should be studied to safeguard ecosystem integrity and public health in areas under the influence of artisanal exploration. Thus, the objectives were to evaluate the total contents, geochemical fractionation, and environmental and human health risks of Ag, As, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, and Zn in artisanal Au mines and nearby agricultural and pasture soils in Água Azul do Norte, southeastern Amazon. Thirty samples (0-20 cm layer) were collected from active and deactivated mining waste deposition piles, as well as from adjacent agricultural and pasture soils. Total contents of TEs were extracted by aqua regia and geochemical fractionation was obtained through sequential extraction. Active mine wastes showed higher total contents of As (12 mg kg^-1), Hg (0.1 mg kg^-1), and especially Ba (168 mg kg^-1), Cr (1141 mg kg^-1), Cu (152 mg kg^-1), and Ni (1133 mg kg^-1). Geochemical fractionation revealed more alarming results in active mining, agricultural, and pasture areas, with moderate global contamination factors (6.1-6.9) and mobility factors exceeding 70%. Potential human health risks, both carcinogenic (indices > 10^-4) and non-carcinogenic (indices > 1), were found for adults and children, especially in active mining areas and with strong contributions from Cr and Ni. Monitoring and mitigation measures should be implemented in artisanal Au mining areas and surrounding soils.

Nano-bio synergistic fermentation (NBSF) was developed to enhance nutrient valorization of agro-residues by integrating zinc oxide (ZnO) nanoparticles with Aspergillus oryzae. Agricultural residues such as rice husk and sugarcane bagasse contain high amounts of structural carbohydrates but are limited by lignocellulosic recalcitrance. In this study, ZnO nanoparticles were characterized using TEM, DLS, zeta potential, XRD, FTIR, BET, UV-Vis, and EDX analyses and subsequently incorporated into solid-state fermentation. Fermentation performance was evaluated based on total soluble nutrients (TSN), protein enrichment, lignocellulosic degradation, and reductions in chemical oxygen demand (COD) and organic load. NBSF increased TSN to 95.3 ± 3.4 mg/g and protein content to 14.6 ± 1.1%, compared with microbial fermentation alone (58.3 ± 2.1 mg/g and 10.7 ± 0.8%, respectively). Cellulose, hemicellulose, and lignin contents decreased by 38.5, 44.2, and 23.1%, respectively. COD and organic load were reduced by 48 and 61%, demonstrating improved environmental performance. Statistical analysis using one-way ANOVA followed by Tukey's HSD confirmed significant differences among treatments (p < 0.001). The results indicate that combining ZnO nanoparticles with microbial fermentation enhances enzymatic hydrolysis, promotes nutrient recovery, and reduces environmental impact, offering a scalable strategy for sustainable agro-residue valorization.

Fluoride (F^-) contamination in groundwater is a major global public health concern. Prolonged intake of F^⁻ above 1.5 mg/L and 10 mg/L may lead to skeletal fluorosis and crippling fluorosis, respectively. The Manyara region, located within Tanzania's fluoride belt in the Eastern African Rift Valley, is one of the areas most affected by elevated F^- levels in groundwater. The extent of F^⁻ pollution and associated health risks in this region remains poorly documented. This study assessed the hydrochemistry, spatial distribution of F^-, non-carcinogenic health risks, and the suitability of groundwater for drinking and irrigation using 225 borehole water samples collected from all six districts of the region. Parameters analyzed included pH, EC, TH, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, Cl^-, SO₄^2-, NO₃^-, and F^-. Irrigation suitability of water was evaluated using EC, %Na, RSC, SAR, Kelley's Ratio, and MAR. Results show that F^- levels ranged from 0.01 to 23.44 mg/L. Overall, 48.00% of samples contained F^- above 1.5 mg/L, and 3.56% of samples exceeded 10.0 mg/L. The Hazard Quotient (HQ) values ranged from 1.00 to.06 (infants), 0.91-6.35 (children), and 0.35-2.42 (adults), indicating elevated health risks, particularly for infants and children. EC values ranged from 63.18 to 8,911.50 µS/cm, with 19.11% of samples exceeding the recommended limit of 2,500 µS/cm. The order of ions was found to be Ca²⁺  > Na⁺  > Mg²⁺  > K⁺ and HCO₃^⁻ > Cl^- > SO₄^2- > NO₃^- > F^-. Most samples were suitable for irrigation, but high salinity poses localized challenges.

Surface sediments from the lower Coatzacoalcos River basin were analyzed to assess the distribution of potentially toxic elements (PTE: Cr, Cu, Pb, Zn), identify sites of ecotoxicological concern, and elucidate the sedimentary processes controlling their accumulation. The Coatzacoalcos River estuary (southern Gulf of Mexico) lies within one of Mexico's major industrial corridors, while small urban settlements and extensive agricultural areas impact the lower basin. Several sampling sites displayed concentrations of Cr (47.5-85.9 μg g^-1), Cu (15.0-37.4 μg g^-1), Pb (6.6-14.6 μg g^-1), and Zn (80.5-178.3 μg g^-1) above background values, although only minor enrichments were observed. Ecological risk indices did not discriminate between sites, indicating an overall low to moderate risk for benthic biota. In contrast, benchmark-based classifications suggested a rare risk for Cu, Pb, and Zn, and an occasional risk for Cr. Principal component analysis revealed that PTEs accumulation is likely influenced by lithogenic sources, fine-grained sediments, and geochemical phases, including organic matter and carbonates. This region has been projected as a strategic hub for national logistics and economic development, and these findings provide valuable information to help mitigate potential environmental impacts from the anticipated industrial expansion.

Former mining activities in the Bétaré-Oya region of eastern Cameroon have generated long-lasting environmental impacts due to the accumulation of unrehabilitated mine residues. This study provides an integrated assessment of the mineralogical, geochemical, spectroscopic, and microtextural characteristics of mine tailings, contaminated soils, and downstream sediments to evaluate their contamination potential. X-ray Diffraction (XRD) analyses show that tailings are dominated by quartz (up to 55%), kaolinite, muscovite, and metallic sulfides including chalcopyrite, arsenopyrite, and galena, while soils and sediments exhibit more heterogeneous silicate-clay assemblages. Fourier-Transform Infrared Spectroscopy (FTIR) identifies strong absorption bands associated with carbonates (1430-875 cm^-1), sulfates (1120-980 cm^-1), and clay-related hydroxyl groups. Geochemically, total carbon (C) ranges from 1.0 to 6.9% in tailings and 1.2-6.4% in soils, whereas sulfur (S) reaches up to 6.5% in some tailings and sediments. Calcium carbonate (CaCO₃) is highly variable, with maximum values of 16% in tailings, reflecting processing residues. Major oxides indicate strong iron enrichment in tailings (Fe₂O₃ up to 13.4 wt%), coupled with elevated Al₂O₃ (up to 35.2 wt%) and SiO₂ variability (25-60 wt%). Silver (Ag) displays anomalous enrichment, reaching up to 8 g/t in tailings, 5 g/t in soils, and 11 g/t in sediments, exceeding typical natural background levels (< 0.1 g/t). Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDX) reveals porous and fractured microtextures, dissolution fronts, and micron-scale hotspots of Pb, Zn, Ag, and As within altered sulfides and secondary Fe-oxides. Collectively, these mineralogical and geochemical signatures indicate a high potential for contaminant release and downstream transfer, particularly during intense tropical weathering and seasonal flooding. The findings underscore the urgent need for site rehabilitation, improved tailings management, and sustained environmental monitoring to mitigate long-term risks to local ecosystems and agricultural zones.

The occurrence characteristics of heavy metals (HMs) in aquatic environments have garnered widespread attention. Industrial wastewater, agricultural runoff, and domestic sewage discharged along the Yellow River in Henan Province pose potential threats to both the river ecosystem and human health. Consequently, the present study elucidated HM sources in the Henan section of the Yellow River via field investigations and model validation. The total concentrations of seven heavy metals (Cu, Pb, Zn, Cr, Ni, Cd, As) in riverbank soils of the studied area ranged from 0.28 (Cd)-798.55 (Mn) mg/kg.. HM levels were generally higher in tributaries than in the main stream, with significant inter-tributary variation (P < 0.05). The spatial distribution of potential ecological risk showed a pyramidal structure, dominated by medium-risk zones (61.50%), followed by high-risk and low-risk areas. Health risk assessment indicated elevated risks for children compared to adults, with oral ingestion identified as the primary exposure pathway (> 90%). Correlation analysis revealed Zn was significantly correlated with other HMs (P < 0.05). Source apportionment via Principal Component Analysis (PCA) combined with the Positive Matrix Factorization (PMF) model quantified contributions as: industrial emissions (28.50%) > agricultural non-point sources (21.70%) > geological background (15.30%) > industrial wastewater (12.80%) > transportation emissions (10.50%) > mining activities (7.00%). Industrial sources were identified as the primary contributor to both ecological and health risks. This study provides a reference and a basis for formulating effective measures to prevent and control HMs enrichment in agricultural soils.

Heavy metal contamination in aquatic environments poses a severe threat to ecosystems and human health due to the non-biodegradability, bioaccumulation, and toxicity of metals such as lead, cadmium, mercury, chromium, and arsenic. Conventional treatment methods often suffer from limitations, including high operational costs, incomplete removal, and secondary pollution. In this context, biocatalytic and enzymatic systems have emerged as promising green alternatives for heavy metal remediation. This review comprehensively examines the current state of enzymatic and biocatalytic approaches for removing heavy metals from water systems. Specific focus is placed on naturally occurring and genetically engineered enzymes, including metallothioneins, phytochelatins, oxidoreductases, and peroxidases, as well as microbial biocatalysts and enzyme-immobilized composites. The underlying mechanisms, such as enzymatic reduction, chelation, biosorption, and bioaccumulation, are discussed in detail. Key factors affecting efficiency, including pH, temperature, enzyme stability, and metal ion speciation, are critically analyzed. Additionally, recent advancements in nano-biocatalysts and immobilized enzyme systems are highlighted for their potential in enhancing selectivity and recyclability. This review not only elucidates the strengths and limitations of biocatalytic systems but also outlines the future directions toward scalable, cost-effective, and sustainable water treatment technologies.