Environmental Science: Processes & Impacts最新文献

Biomass burning produces extensive pyrogenic dissolved organic matter (PyDOM), but the differences in compositions and photoactivities between PyDOM from char residues and smoke aerosols (referred to as PyDOM_char and PyDOM_aerosol) remain poorly understood. Here, we systematically compared the composition and photoactivity of PyDOM_char and PyDOM_aerosol coproduced by open-air burning of rice straw. At the bulk level, PyDOM_aerosol exhibited lower ultraviolet-visible absorption but higher fluorescence intensity than PyDOM_char. Additionally, PyDOM_aerosol had a lower weight-averaged molecular weight (1940 Da) than PyDOM_char (2601 Da). At the molecular level, 3594 and 2734 molecular formulae were identified for PyDOM_aerosol and PyDOM_char, indicating greater chemical diversity of PyDOM_aerosol. PyDOM_aerosol was enriched in aromatic compounds (19.1% vs. 15.8%), aliphatic compounds (12.3% vs. 5.3%), carbohydrate-like compounds (3.9% vs. 0.02%), and N/S-containing molecules (43.9% vs. 20.6%) compared to PyDOM_char. Accordingly, PyDOM_aerosol more effectively promoted ³DOM* and ¹O₂ formation under simulated sunlight. Our findings revealed structural and photoactivity differences between PyDOM_char and PyDOM_aerosol, informing their environmental effects.

Rewetting of previously drained wetland soils can induce rapid redox shifts that influence mercury (Hg) cycling and methylmercury (MeHg) production. We investigated how prior exposure to common metal-salt and biopolymer coagulants influences Hg transformations during wetland soil rewetting and whether organic matter (OM) availability modulates these effects. Wetland soils (∼300 µg kg^-1 total Hg) were incubated in triplicate soil-water microcosms for 16 days following rewetting. Treatments included soils previously exposed to ferric sulfate, polyaluminum chloride, or a chitosan-based coagulant, alongside untreated controls. Upon rewetting without additional OM, redox potential declined to ∼250 mV, consistent with manganese-reducing conditions, and MeHg concentrations remained relatively low in water (0.05-0.18 ng L^-1) and soils (1-2 µg kg^-1) across all treatments. In contrast, addition of algal-derived OM (Spirulina powder) rapidly decreased redox potential to 0-100 mV and produced a short-lived pulse of MeHg formation in all treatments, with aqueous MeHg peaking at ∼30-40 ng L^-1 and soil MeHg at ∼6-8 µg kg^-1 on days 2-4 before declining. Coagulant treatments increased transient inorganic Hg concentrations in overlying water (45-75 ng L^-1) relative to controls (∼30 ng L^-1) but did not enhance higher MeHg production. Results demonstrate that OM-driven redox dynamics, rather than prior coagulant exposure, control transient MeHg production during wetland soil rewetting, highlighting how episodic carbon inputs can regulate mercury transformation in managed and natural wetlands.

Dihydroxybenzenes such as catechol are major aromatic constituents of biomass-burning emissions and are readily deposited onto atmospheric particle surfaces, where they undergo heterogeneous oxidation. Here, hydroxyl radical (HO˙) production during the ozonolysis of catechol at the air-solid interface is quantified using an indirect fluorescent probe approach. Thin films containing catechol and molecular scavengers were exposed to ozone (0.5-112 ppmv) under controlled relative humidity (RH = 0-85%) conditions, and HO˙ formation was inferred from the production of hydroxylated probe products. Significant HO˙ production was observed under all conditions, with interfacial production rates increasing systematically with both ozone concentration and RH, reaching 3.1 × 10¹⁰-1.2 × 10¹² molecules cm^-2 s^-1 under humid conditions (85% RH). Quantitative kinetic analysis reveals a linear dependence of HO˙ production on [O₃(g)], consistent with pseudo-first-order behavior under oxidant-limited conditions, and enabling derivation of an effective HO˙-forming uptake probability. Concurrently, the interfacial reaction velocity increases exponentially with RH, reflecting enhanced oxidant uptake, interfacial transport, and reactive turnover in hydrated films. By relating the measured reaction velocity to kinetic gas theory, an effective HO˙-forming uptake probability of γ_HO˙,eff ≈ (5.4 ± 1.9) × 10^-10 is obtained. Comparison with independently reported ozone uptake coefficients for catechol films (γ_O3) yields an inferred HO˙ formation efficiency of Y_HO˙ = (3.4 ± 1.2) × 10^-5, indicating that hydroxyl radical production proceeds through a measurable secondary pathway of heterogeneous ozonolysis. These results demonstrate that surface-mediated oxidation of aromatic films constitutes a non-photochemical source of hydroxyl radicals under atmospherically relevant conditions. The strong dependence on relative humidity suggests that interfacial hydration modulates both ozone uptake and radical formation, providing a quantitative framework for evaluating this process as a sensitivity pathway in multiphase atmospheric oxidation chemistry.

PBDEs have been regulated as POPs for nearly two decades but remain ubiquitous in the global environment and in humans. In this study, we used a dynamic multimedia model to investigate the impact of climate change on the fate and transport of PBDEs under temporally constant emission conditions. Under RCP 8.5-based meteorological conditions projected for South Korea through 2100, nationwide 30-year mean concentration ratios relative to the baseline period ranged from 0.68 to 1.29 across air, freshwater, and soil, whereas annual mean ratios ranged from 0.44 to 1.86. Interannual variability was greater in freshwater and soil than in air, with maximum annual changes of -56% in soil, +86% in freshwater, and +21% in air. The major meteorological factors affecting environmental concentrations were wind speed and rainfall frequency for air, rainfall amount and temperature for soil, and rainfall amount and frequency for freshwater. Our findings show that chemicals with physicochemical properties similar to those of PBDEs may experience diminished atmospheric mobility and increased migration from terrestrial surfaces to freshwater under changing climate conditions.

Wular Lake, a Ramsar wetland in the Kashmir Himalaya and one of South Asia's largest freshwater lakes, is under growing anthropogenic pressure. This study assessed six potentially toxic elements (PTEs: Cr, Ni, Cu, Zn, Cd, and Pb) in 22 surface-sediment samples using contamination indices, ecological and probabilistic (Monte Carlo) health-risk models, and APCS-MLR source apportionment. The geoaccumulation index (I_geo, 1-2) and the Nemerow pollution index (P_N) rated every site as moderately to heavily polluted. The potential ecological risk index (RI 66-132, mean 98) indicated moderate ecological risk overall, rising to considerable risk at seven hotspot sites; consistently, the mean Probable Effect Concentration Quotient (mPEC-Q) exceeded 0.5 at 12 of 22 sites, driven by Ni and Cr. Monte Carlo simulation showed no non-carcinogenic risk (HI ≪ 1) and acceptable carcinogenic risk (TCR ≈ 10^-5), higher in children, with Cr and Ni dominant. APCS-MLR resolved a chromium-dominated natural source and a mixed anthropogenic source (Pb, Cu, Zn, Cd, and Ni; ∼65% of the load). Targeted control of anthropogenic inputs would curb the controllable risk and support conservation of this Ramsar site, which contributes to several United Nations Sustainable Development Goals (SDGs).

This study investigated the occurrence, distribution, and ecological risks of 29 herbicides in water bodies surrounding a landfill in North China. Analysis revealed that 24 herbicides were ubiquitously detected, though at trace concentrations (ng L^-1 level). The herbicide compositions varied significantly among the leachate, groundwater, and surface water samples. Spatial distribution, together with principal component analysis and Pearson's correlation analysis, indicated diverse sources of herbicide contamination in the surrounding waters. However, the landfill is effective in preventing herbicides from spreading into adjacent aquatic systems via leachate, which validates the reliability of its engineered anti-seepage design. Three primary components were identified within the dissolved organic matter (DOM) using parallel factor analysis. Notably, the percentage of tyrosine-like compounds (C1) in the DOM, combined with the humification index (HIX), has been proposed as a potential indicator for assessing the extent to which water bodies are affected by leachate. Generally, a low C1 proportion coupled with a high HIX suggests a significant influence from landfill or similar anthropogenic inputs. In terms of ecological risk, sulfonylurea herbicides (SHs) posed the highest concern, whereas amides (AHs) and triazine herbicides (THs) exhibited lower risks or require further evaluation. Eleven specific herbicides (5 SHs, 4 THs, and 2 AHs) were identified as high-priority toxic substances warranting special attention in future research. These findings highlight the need for continued monitoring and management of herbicide contamination in landfill environments to safeguard water resources.

Although nonstick cookware is widely used in everyday life, the mechanical wear of its coatings has been proposed as a potential source of particulate release to aquatic environments, but it remains poorly investigated. In this study, we evaluated the composition, heterogeneity, and ecotoxicological effects of cookware abrasion-derived particulates (CADPs) generated under a controlled dry-abrasion protocol using nonstick cookware and a stainless steel scourer, using Physalaemus cuvieri and Allium cepa as complementary model systems. CADPs were characterized by optical microscopy, UV epifluorescence microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and Raman spectroscopy. Organisms were exposed to CADPs at 0.1, 1.0, and 10 mg L^-1 (CADP-0.1, CADP-1.0, and CADP-10, respectively) for 7 days, and morphometric, developmental, biochemical, DNA damage, and cytogenetic endpoints were evaluated. Characterization revealed a heterogeneous, multiphasic particulate fraction composed of dark fragments consistent with coating delamination, metallic particles, and hybrid structures, with marked occurrence of F, C, O, Fe, Al, Ti, and Cr, together with minor elements likely associated with pigments, fillers, additives, or abrasive residues. No mortality was observed in either model. However, in tadpoles, CADP-10 reduced developmental progression, increased ROS, MDA, nitrite, catalase, esterases, CYP450-type oxidase, total proteins, and triglycerides, reduced total soluble carbohydrates, and increased the frequency of nucleoids showing intermediate DNA damage, without increasing the overall mean DNA damage. In A. cepa, CADPs reduced root emission and integrated root growth, altered root growth patterns, increased MDA and nitrite levels, reduced ROS and SOD activity, and impaired mitotic activity and progression, without evidence of recurrent chromosomal damage. Multivariate analyses confirmed distinct biological response profiles among treatments, and the integrated Cross model Integrated Biological Disturbance Score indicated greater overall sensitivity in A. cepa and intensified biological disturbance at CADP-10. These findings demonstrate that CADPs generated under controlled dry-abrasion conditions constitute a multiphasic bioactive particulate mixture capable of inducing integrated sublethal responses in distinct biological systems. In contrast, their release under actual household washing conditions remains to be determined.

The persistence of veterinary antibiotics in soils, particularly in alpine regions, poses environmental risks. A critical knowledge gap exists regarding the degradation mechanisms under freeze-thaw cycles (FTCs), specifically the interplay between iron-manganese oxide-mediated abiotic processes and microbial processes. To address this, we employed loess as the experimental medium and selected oxytetracycline (OTC) and ciprofloxacin (CIP) as representative antibiotics, conducting laboratory experiments to systematically evaluate the effects of sterilization, varying iron-manganese oxide concentrations (0-5.0%), and FTCs on antibiotic degradation kinetics. The results showed that microbial degradation was the primary removal pathway. Sterilization inhibited degradation, reducing the OTC and CIP degradation rates by 66.7% and 43.0%, respectively. The influence of iron-manganese oxides varied depending on the antibiotic. They promoted OTC degradation, with maximum enhancement (70.8%) at 1.25% addition of the catalyst. For CIP, only 1.25% addition promoted degradation, whereas 2.5% and 5.0% additions suppressed the degradation rates by 2.3% and 5.2%, respectively. FTCs delayed antibiotic degradation by inhibiting microbial activity and affected non-biotic degradation by altering soil organic matter and the microenvironment. With iron-manganese oxides present, freeze-thaw impacts varied based on the antibiotic molecular structure and mineral surface properties. This study makes a substantive contribution by elucidating the key factors governing OTC and CIP degradation in alpine loess regions and, importantly, revealing the contrasting regulatory effects of iron-manganese oxides on different antibiotics under FTCs. These findings provide critical parameters for assessing the environmental behavior and risks of antibiotics, thereby informing the development of targeted pollution mitigation strategies.

Water-stable aggregates (WSAs) are a key indicator of soil structural stability and influence water erosion potential. Microplastics (MPs) have been shown to impact WSA formation and their association with WSAs may strongly influence their transport in soils. However, the effect of MPs on WSA formation and their simultaneous association with WSAs has not yet been addressed. This study assessed how MP polymer composition [polylactic acid (PLA) and polyethylene terephthalate (PET)], size (<63 µm and >250 µm) and concentration (0.2, 0.5, and 1 wt%) as well as soil texture (loam and loamy sand) affect WSA formation and MPs-WSA association over a two-week laboratory incubation. The formation of WSAs was decreased most (i.e., 10-13%) by small PLA fragments at low to medium concentrations. Other treatments showed weak or no effects. Across all incubations, MPs were predominantly associated with WSAs (>65%), whereas large PLA fragments at low and small PLA fragments at high spiking concentrations showed comparatively less association. Collectively, MP polymer type, size, and concentration in soil impacted WSA formation and their association with WSAs, implying that the mutual interactions of MP presence and aggregation processes in soils have the potential to affect aggregate stability and particularly MP transport.

Agricultural canal-lake systems are potential hotspots for greenhouse gas (GHG) emissions; however, existing studies have largely focused on natural water bodies or single-type water bodies, with limited research on the continuum. Therefore, this study analyzed the dynamics of CO₂ flux (F_CO2) in the agricultural canal-Lake Ulansuhai continuum within the Hetao Irrigation District of Inner Mongolia and quantified the annual CO₂ emissions (F_CO2total) from agricultural canals and lakes on the Inner Mongolia Plateau. The results showed that agricultural canals were persistently supersaturated with CO₂ and released it to the atmosphere, with their average F_CO2 (49.43 ± 37.28 mmol per m² per day) being significantly higher than that of the connected Lake Ulansuhai and the average level of Chinese lakes. Although the average F_CO2 of Lake Ulansuhai was higher than that of major freshwater lakes in China, some areas of the lake acted as a net CO₂ sink during the autumn irrigation period, revealing a dynamic shift between a carbon source and sink in cold-arid lakes. The annual CO₂ emissions from agricultural canals and lakes on the Inner Mongolia Plateau were 0.0097 Tg C per year and 0.22 Tg C per year, respectively, providing key baseline data for regional carbon budgeting. This study transcends the limitations of traditional fragmented research approaches by systematically quantifying the differences in CO₂ emissions between canals and lakes within the continuum and highlights the role of agricultural canal-lake systems as regional carbon emission hotspots. The findings provide a scientific basis for salinization control, eutrophication prevention, and water environment protection of the Yellow River, and also offer critical data support for regional ecological management and carbon accounting in cold and arid regions.