Search Results (701)

Per- and polyfluoroalkyl substances (PFASs) are persistent environmental contaminants widely recognized as “forever chemicals” due to the exceptional stability of their carbon–fluorine (C-F) bonds. Their widespread occurrence in water, soil, sediments, and biota, coupled with increasing evidence of toxicity, bioaccumulation, and long-range transport, has intensified the search for sustainable remediation strategies. Conventional remediation technologies for PFASs have been widely applied but remain constrained by several technical and environmental limitations, such as incomplete mineralization, high energy requirements, secondary waste generation, and the formation of toxic transformation products. Moreover, many conventional treatment processes were not originally designed to handle the chemical stability and structural diversity of PFASs, resulting in variable removal efficiencies across different compounds. Bio-based strategies for PFAS remediation, particularly those targeting C-F bond cleavage and biological defluorination, are gaining attention due to the unique challenges posed by the chemical stability and environmental persistence of these “forever chemicals”. This review addresses the fragmented nature of PFAS remediation research by integrating biological and physicochemical strategies and critically examining mechanisms of C-F bond cleavage and defluorination. Emerging technologies, including bioelectrochemical systems, photocatalytic and electrochemical defluorination, adsorption-assisted degradation, plasma treatment, hydrothermal processes, and synthetic biology approaches, are evaluated in relation to their degradation efficiencies, defluorination capacities, and applicability in diverse environmental matrices. Particular attention is given to integrated “capture-and-destroy” systems that combine adsorption with catalytic or biological degradation to enhance remediation efficiency and reduce energy demand. PFAS treatment performance varies markedly across scalability, destruction, and cost. Key knowledge gaps and future perspectives are outlined, emphasizing the need for scalable, energy-efficient, and environmentally sustainable remediation technologies capable of achieving complete PFAS mineralization in complex environmental systems. Full article

Quantitative probabilistic risk assessment of trace metal(loid)s in sediment is highly important for the protection and management of aquatic ecosystems. In this study, surface sediment from the Huaihe River (Anhui Province, China) was collected. In addition to the total content, the bioaccessible fractions of trace metal(loid)s (Cu, Pb, Zn, Cr, Cd, As, Hg, and Ni) were investigated using the diffusive gradients in thin films (DGT) technique. Multiple-level risk assessments, including the toxicity unit (TU), risk quotient (RQ), and probabilistic risk assessment (PRA), were conducted based on the species sensitivity distribution (SSD) to evaluate the probabilistic risk of trace metal(loid)s to aquatic biota. The results reveal that the Cu, Pb, Zn, Cr, and Ni levels were higher than the corresponding background levels; however, the total levels were lower than those reported in previous studies, which might be attributed to dredging activities in recent years. The ∑TU values suggested that the trace metal(loid)s in the sediment posed a low toxicity risk. The DGT-labile concentration values were low, demonstrating the low bioaccessibility of the trace metal(loid)s. The DGT-SSD coupled with the PRA revealed that the trace metal(loid)s had a 0.01–3.30% probability of adversely affecting the aquatic biota. Furthermore, the combined toxicity, calculated by summing probabilities of individual metal(loid), indicated a 5.58% probability of adverse effects on aquatic biota. Full article

Traditional monitoring frameworks heavily rely on static, total heavy metal concentrations and deterministic indices, failing to capture how climate-driven stressors and micro-interface interactions alter the stability, speciation, and bioavailability of toxic metals. This review synthesizes the state-of-the-art literature at the intersection of hydrology, geochemistry, microbial ecology, and toxicology to address this gap. We investigate how shifting redox (Eh-pH) gradients and climate-forced hydrological extremes—ranging from drought-induced sediment acidification to flood-driven shear stress—accelerate the reductive dissolution of iron/manganese oxyhydroxides. This process consequently triggers seasonal pulses of bioavailable metals. Furthermore, we evaluate how aged microplastics act as dynamic vector interfaces, altering competitive adsorption kinetics and biological uptake. Crucially, we highlight the heavy metal-microbiome-antibiotic resistance axis, demonstrating how sublethal metal exposure drives the co-selection and proliferation of antibiotic resistance genes (ARGs) via mobile genetic elements, revealing an indirect public health hazard. Finally, we critique deterministic assessments and advocate for probabilistic modeling via Monte Carlo simulations to capture exposure heterogeneity. By bridging macro-scale forcing with microscopic chemical and biological transformations, this review provides a comprehensive synthesis for shifting regulatory frameworks toward dynamic, bioavailability-based ecological governance. Full article

The Anning River, traversing the mineral-rich Panxi region, is highly susceptible to contamination by potentially toxic elements (PTEs). This study systematically investigated the contamination profiles, source apportionment, and probabilistic human health risks of eight PTEs in the surface sediments of the basin. Index-based evaluations revealed that Cd acts as the dominant ecological threat, exhibiting extreme enrichment, whereas V, Cr, and Ni reflect natural background signatures. Receptor modeling via Positive Matrix Factorization (PMF) successfully decoupled four distinct sources: mining and smelting emissions (Cd, Zn), natural lithogenic weathering (V, Cr, Ni), mixed traffic/urban inputs (Pb, Cu), and a Tl-specific mixed source. Crucially, while deterministic approaches suggested safe exposure levels, probabilistic Monte Carlo simulations uncovered hidden vulnerabilities: children face a striking 60.51% probability of exceeding the acceptable total carcinogenic risk (TCR) threshold of 1.0 × 10⁻⁴, primarily governed by Cr and Ni. These findings underscore the urgent need for differentiated environmental management in similar mining-impacted basins. Specifically, stringent source controls for Cd must be implemented alongside exposure pathway interruptions to safeguard vulnerable demographics from Cr and Ni. Full article

The contamination of microplastics (MPs) and heavy metals (HMs) in water has caused widespread concern, while their effects on submerged macrophytes have rarely been reported. Experiments were carried out to investigate the toxic effects of polyamide microplastics (PAMPs; 0.1%, 0.3%, and 1.0% w/w) and cadmium (Cd; 0.3 and 1.0 mg/L), alone or in combination, on the submerged macrophyte Vallisneria natans (V. natans). The results showed that PAMPs significantly reduced Cd accumulation in leaves (decrease of 2.38%~26.12%) but elevated Cd accumulation in roots. Both Cd exposure and high PAMP exposure alone inhibited plant growth. The combined stress showed concentration-dependent effects: the low Cd concentration (0.3 mg/L) and PAMPs synergistically exacerbated toxicity (synergism, MDR > 1.3), as PAMPs disrupted the sediment structure and enhanced the bioavailability of Cd, whereas when V. natans was co-exposed to the high Cd concentration (1.0 mg/L) and PAMPs, the PAMPs blunted the toxicity of Cd by efficiently adsorbing it (antagonism, MDR < 0.7). Both individual and combined exposures decreased chlorophyll a and chlorophyll b synthesis and increased superoxide dismutase (SOD) and peroxidase (POD) activities as well as malondialdehyde (MDA) content in plant tissues. However, exposure to low and medium concentrations of MPs (0.1% and 0.3% w/w) alone had positive effects on plant growth and photosynthesis systems, while combined exposures exacerbated the damaging effects of PAMPs on the antioxidant defense system in V. natans. These results allow for a better understanding of the synergistic effect of co-contamination of microplastics and heavy metals in freshwater ecosystems, and highlight the necessity of ecological risk assessment during phytoremediation using submerged macrophytes. Full article

This study systematically investigated microplastics (MPs) in Pingshan River, Shenzhen—a representative urban river with short channel length, rapid flow, and limited environmental capacity. Surface water and sediment samples from seven sites were analyzed for MP abundance, size, morphology, color, and polymer composition. Results revealed significant MP pollution: surface water abundance ranged from 132 to 423 items/L (mean 311.42 ± 90.78 items/L), while sediment abundance ranged from 334 to 756 items/kg (mean 508.85 ± 151.79 items/kg). Spatial heterogeneity was pronounced, with the highest abundance at a construction-influenced site (Site 6) and the lowest at a less-impacted site (Site 2). MPs were predominantly 300–1000 μm in size. Fibers dominated surface water, while fragments prevailed in sediment. Transparent particles constituted >77% of all MPs. Polymer composition was dominated by polypropylene (PP) and polyethylene (PE). Key factors controlling spatial distribution included proximity to construction/industrial activities, aquatic vegetation cover, and hydrological conditions during the dry season. Polymer hazard risk index (H) classified all sites as Category II (10 ≤ H < 100), indicating low ecological risk despite high abundances. This research provides a scientific foundation for targeted pollution control in urban river systems, emphasizing the need to consider both abundance and polymer-specific toxicity in risk assessment. Full article

High-mountain lotic ecosystems in the tropical Andes are increasingly threatened by agricultural expansion and seasonal hydrological variability. This study evaluates structural water quality shifts and benthic macroinvertebrate community assembly across an environmental degradation gradient in the La Chorrera micro-basin (Boyacá, Colombia). A weighted multiplicative Water Quality Index (mWQI), originally developed in previous literature, was implemented and validated alongside biotic scores (BMWP/Col) and Canonical Correspondence Analysis (CCA) across 16 sampling points during contrasting wet and dry seasons. The results demonstrate that intense precipitation during the wet season introduces a volumetric dilution effect, maintaining high ecological quality scores (mWQI > 80.0) even in deeply modified agricultural sectors. Conversely, severe baseflow contraction during the dry season triggers pollutant concentration, driving total phosphorus to hyper-eutrophic peaks (9.20 mg/L) and forcing a complete mathematical collapse of the index (mWQI = 0.00). The CCA biplot confirmed that seasonal chemical filters combined with hypoxia (<60% oxygen saturation) eliminate highly responsive macroinvertebrate orders (Ephemeroptera, Plecoptera, Trichoptera), leading to absolute dominance of hypoxia-tolerant opportunists (Chironomidae and Oligochaeta). The benthic community shifted from physical stress (sedimentation) during the wet season to chemical stress (nutrient toxicity and oxygen depletion) during the dry season. The multiplicative framework effectively isolates localized ecological tipping points, providing a high-sensitivity baseline tool for targeted watershed restoration in tropical alpine regions. Full article

Chlorinated paraffins (CPs) are recognized as a novel class of persistent organic pollutants (POPs) and are categorized into short- (SCCPs, C_10–13), medium- (MCCPs, C1_4–17), and long- (LCCPs, C_≥18) chain CPs considering the carbon-chain length. Among them, SCCPs possess lower molecular weights, higher vapor pressures, and greater water solubilities compared to their longer-chain counterparts (MCCPs and LCCPs), which promote their environmental release. Consequently, SCCPs were designated as POPs of concern under the Stockholm Convention in 2017. This review concludes the recent research progress of SCCPs in China from 2015 to present, and we present a comprehensive overview of SCCP concentrations, encompassing diverse environmental matrices and human tissues, for example, air, water, soil, sediments, biota, food, human placenta, breast milk, blood, and organs (fat, kidney, liver, brain, bone, etc.). Whereafter, we summarize the development of SCCPs determination methods, benefiting from quantifying relative carbon-chain length and chlorine content of SCCPs correctly. Moreover, toxicity, toxicokinetics, and adverse health effects of SCCPs in humans from China are concluded and discussed. Meanwhile, we review the existing control and treatment technologies for SCCPs. Lastly, we describe some noteworthy and prospective issues that are worthy of further study. In the future, the relevant studies are still necessary to keep up with consecutive monitoring and evaluation of SCCP levels and relative potential health impacts in China. Full article

Polycyclic aromatic hydrocarbons (PAHs) represent a major class of ubiquitous environmental pollutants, posing significant risks to ecosystems and human health due to their persistence, toxicity, and potential for bioaccumulation. This review provides a comprehensive synthesis of current scientific knowledge on PAHs, integrating insights from chemical kinetics, environmental fate, and toxicological mechanisms. The fundamental structural chemistry of PAHs and its direct influence on their physicochemical properties and environmental properties are discussed. The major anthropogenic and natural sources of PAHs are detailed, alongside the chemical kinetics behind their formation during incomplete combustion and their transformation in environmental media. Unlike previous reviews that address PAH sources, remediation, or health effects as separate topics, this review uniquely traces the mechanistic continuum from molecular formation kinetics through physicochemical partitioning and environmental transport to toxicological endpoints, providing a causally linked framework for understanding how structural properties ultimately determine biological outcomes. A central focus is placed on the environmental fate and transport of PAHs across atmospheric, aquatic, and terrestrial compartments, highlighting processes such as gas–particle partitioning, sediment accumulation, and long-range transport. The review further elucidates the complex toxicological pathways of PAHs, including metabolic activation to reactive intermediates, DNA adduct formation, oxidative stress, and their roles in carcinogenesis and other systemic health effects. The analysis reveals strong scientific consensus on the carcinogenic mechanism of parent PAHs via CYP450-mediated metabolic activation to diol-epoxide intermediates while identifying critical areas of uncertainty: the current regulatory framework based on 16 priority PAHs underestimates total carcinogenic risk by a factor of 2–5, mixture toxicology remains poorly characterized, and dose–response relationships for non-cancer endpoints (cardiovascular, neurodevelopmental, immunotoxic) lack the quantitative data needed for robust risk assessment. Finally, human exposure pathways and health risk characterization approaches are discussed, highlighting the need for cumulative, mixture-based assessment frameworks. Full article

The Santiago River is a highly anthropogenically impaired lotic system globally, yet the mechanisms governing its contaminant transport remain poorly understood under static monitoring paradigms. This study evaluates how hydrological forcing dictates the mobilization and bioavailability of trace metals by integrating a 15-year public hydrochemical database from 10 monitoring nodes with SAR-derived discharge estimates and thermodynamic metal modeling (PHREEQC). To validate the structural integrity of the mass load estimates against hydrometric uncertainties, a deterministic boundary-sensitivity analysis was conducted. Results empirically refute the classical dilution paradigm, introducing the “Anthropogenic Pulse” to describe the non-linear acceleration of pollutant export during high-flow events (discharge Q surging from 36.62 to 286.13 m³/s). While climate-driven parameters follow seasonal cycles, industrial stressors (COD, Pb, Cd) remain in a chronic steady state, decoupling from volumetric dilution. Based on coupled × CQ × C (discharge × concentration) estimates, this dynamic induces a synchronized flushing of toxic burdens, exporting monthly peak loads exceeding 51,000 kg of Zinc, 6500 kg of Lead, and 3100 kg of Cadmium. Thermodynamic simulations reveal that this hydrological flushing functions as a chemical activator; the seasonal dilution of natural Alkalinity and Hardness suppresses the river’s theoretical buffered pH (from 8.5 to 7.0), maintaining metals in their uncomplexed free-ion states (Me²⁺). Modeling indicates that nearly 90% of the exported Cadmium remains in this highly labile, toxic form due to a dual coupling with both river Discharge (r_s = 0.87) and pH (r_s = 0.79). The identification of stochastic arsenic peaks 100 times above regulatory limits at Paso de Guadalupe (RS-08) underscores the failure of concentration-based monitoring. Our findings suggest that restoration strategies should shift toward mass-loading-based regulatory frameworks and targeted sediment management at critical nodes to mitigate the chronic export of bioavailable industrial waste. Full article

Particulate emerging contaminants (PECs) pose increasing ecological risks due to their widespread occurrence and complex environmental behaviors, yet their heterogeneous toxic mechanisms remain poorly understood, especially under environmentally relevant conditions and concentration gradients. Here, Chlorella vulgaris was used as a model organism to systematically compare the effects of polystyrene nanoparticles (PSNPs), silver nanoparticles (AgNPs), and titanium dioxide nanoparticles (TiO₂NPs) across environmentally relevant and elevated concentrations (100 μg/L and 10 mg/L). Distinct toxicity pathways were identified among PEC types. PSNPs primarily induced chronic interference via particle–cell interactions, heteroaggregation, sedimentation-driven shading, and extracellular polymeric substance (EPS) regulation, rather than ROS-dominated toxicity. In contrast, AgNPs exhibited transformation-driven toxicity, undergoing intracellular speciation into Ag₂S, AgCl, and Ag⁺, which triggered oxidative stress, membrane damage, and lipid peroxidation. TiO₂NPs showed relatively high bioavailability and persistent oxidative stress effects. These results demonstrate that PEC toxicity evolves with particle type and concentration. Importantly, oxidative stress alone is insufficient to capture PEC ecotoxicity, which also involves the long-term impacts on algal behavior, sedimentation dynamics, and energy metabolism. This study provides mechanistic insights into PEC-induced algal toxicity and supports the source-oriented management of particulate pollutants in aquatic environments, particularly in hotspot scenarios such as wastewater discharge and sediment resuspension. Full article

This study evaluates the characteristics and environmental behavior of river sediments impacted by coal mining in the southern coal region of Santa Catarina, Brazil. Sediments accumulated in mining-affected rivers represent an environmental liability due to the presence of potentially toxic elements and their limited management options. In this context, ceramization is investigated as an alternative strategy for reducing contaminant mobility through thermal treatment of sediments collected at four sampling points (PU1–PU4) along the Urussanga River. Initially, leaching and solubilization tests were performed to assess the mobility of chemical elements, and the raw sediments were further characterized by chemical, mineralogical, and thermal analyses. Subsequently, ceramic specimens were produced from the sediments and subjected to thermal treatment at 1100 °C. After firing, the specimens were re-evaluated through leaching and solubilization assays to verify changes in contaminant mobility after the ceramization process. The results showed that raw sediments exhibited aluminum, iron, and manganese concentrations in the solubilized extract that exceeded regulatory thresholds, particularly for iron, which reached up to 21.91 mg/L. After thermal treatment, a substantial reduction in the solubility of these elements was observed, with concentrations falling below the established limits at all sampling points. This reduction in mobility is likely associated with physicochemical transformations occurring during firing, including matrix densification and the incorporation of elements into less soluble phases, as reported in previous ceramic processing studies. Overall, the findings demonstrate that ceramization represents a promising strategy for reducing contaminant mobility in coal mining-impacted river sediments, offering a viable and environmentally friendly alternative for sediment management and valorization. Full article

Potentially toxic elements (PTE) are persistent contaminants in coastal systems and may accumulate in marine organisms, with relevance for both environmental monitoring and seafood safety assessment. This study provides an exploratory cross-biota assessment of Cd, Cr, Cu, Ni, and Pb in fishery resources from the Romanian Black Sea in 2024. The dataset included 24 composite samples and 120 analyte-level observations across bivalves, gastropods, pelagic fish, and demersal fish. Tissue concentrations were integrated with regulatory maximum levels, bioconcentration factors (BCF), biota–sediment accumulation factors (BSAF), and adult dietary risk indices, including estimated daily intake (EDI), target hazard quotient (THQ), and total target hazard quotient (TTHQ). Within the limits of this single-year dataset, Cd and Pb concentrations were generally higher in bivalves than in fish and gastropods, whereas Cr showed higher values in several fish samples, particularly pelagic fish. Cd was the main element of concern, with regulatory exceedances occurring mainly in bivalves and fewer exceedances in pelagic fish, while Pb exceedance was isolated. BCF and BSAF supported the relevance of Cd as a priority element but were interpreted only as descriptive tissue–water and tissue–sediment ratios, not as evidence of specific uptake pathways. Low abiotic Cd concentrations may have inflated some ratio-based values, and Cr interpretation remains limited by the absence of Cr speciation and dissolved/particulate partitioning data. The adult dietary risk assessment did not indicate substantial non-carcinogenic concern, as all individual THQ values and cumulative TTHQ values remained below 1. Overall, the findings support continued PTE monitoring in the Romanian Black Sea, using sessile bivalves as indicators of local environmental contamination and including gastropods and representative pelagic and demersal fish species of ecological and fisheries relevance to capture contaminant patterns across benthic and mobile fishery resources. Future monitoring should improve species-level replication, integrate metal partitioning in abiotic matrices, and include additional contaminants of seafood safety relevance, particularly Hg and As. 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

Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants of concern in aquatic environments because of their stability, mobility, and resistance to conventional degradation. This review examines PFAS remediation technologies in water and wastewater treatment, with emphasis on membrane filtration, advanced oxidation processes, and biological approaches. Although many studies have reported high removal efficiencies, the limitations of these techniques are numerous, including membrane fouling, high energy consumption, incomplete destruction, formation of short-chain transformation products, and the management of concentrated residual streams. As a result, PFAS remain bioavailable in receiving waters for biological uptake, leading to ecological consequences in aquatic systems. PFAS can enter organisms through water, diet, sediment contact, and maternal transfer, and their bioaccumulation is associated with growth inhibition, developmental toxicity, endocrine disruption, oxidative stress, immunotoxicity, neurobehavioral changes, and hepatic damage. These effects can persist even when treatment systems achieve reductions in water concentrations. Therefore, PFAS management should be assessed not only by removal efficiency but also by the capacity of treatment systems to reduce trophic exposure in food webs. Full article