Environmental Science: Processes & Impacts最新文献

Oxidized organics on atmospheric particle surfaces strongly influence water uptake, toxicity, and heterogeneous reaction kinetics. However, the nature of surface species and their interaction with gas-phase radicals are not well-understood. Here, experiments probed the impact of gas-phase HO₂ and RO₂ radicals on the surface products formed in the reaction of gas-phase OH with solid glutaric acid (GA) particles at 298 K and 1 atm in air. Hydroxyl radicals were formed from the reaction of tetramethylethylene (TME) with ozone in a flow system and reacted with atomized, dried GA particles. Surface products including alcohols, carbonyls, hydroperoxides, and organic peroxides were detected using Matrix Assisted Ionization in Vacuum - Mass Spectrometry (MAIV-MS), an emerging surface-sensitive technique. A product tentatively identified as an ester from reactions between surface-bound GA and gas-phase radicals was also observed. Concentrations of gas-phase radicals (RO₂ and HO₂) were varied by altering TME concentrations or by adding methanol or acetone, significantly impacting the observed product distribution. Particle size was also varied to alter the surface density of RO_2(surf) and explore the role of surface availability. The results show that the fates of surface-bound radicals are largely determined by reactions with gas-phase HO₂ or RO₂. This complex competition is central in determining the surface composition of organic particles, and therefore the chemistry and environmental impacts of oxidized airborne organic particles.

Conventional monitoring for per- and polyfluoroalkyl substances (PFAS) in engineered water systems can underestimate total PFAS discharge by using targeted methods that capture mostly terminal perfluoroalkyl acids (PFAAs) but omit many important PFAS such as oxidizable precursors. We combined targeted LC-MS/MS with the total oxidizable precursor (TOP) assay to quantify PFAS composition and precursor contributions in municipal wastewater and urban stormwater in six communities. Target PFAS concentrations ranged from 25-108 ng L^-1 in wastewater treatment plant (WWTP) influent, from 20-231 ng L^-1 in WWTP effluent, and from 16-85 ng L^-1 in stormwater. However, total oxidizable precursors comprised up to 92% of total PFAS in WWTP influent, 70% in effluent, and 59% in stormwater. In WWTP effluent, the proportion of untargeted precursor PFAS was significantly higher at facilities with secondary treatment hydraulic retention times (HRTs) <1 h (mean = 59.7%) than at facilities with longer HRTs (>1 h; mean = 39.3%; Welch's t-test, p = 0.008), indicating that limited biological treatment duration may constrain precursor biotransformation. Collectively, the six WWTPs discharged approximately 26 kg per year of total PFAS, of which 47% (12.3 kg per year) consisted of untargeted PFAA precursors. Total stormwater PFAS loads were episodic (approximately 1.2-31.5 g per event) and similarly deliver substantial untargeted PFAA precursor mass (approximately 0.7-8.7 g per event) to receiving waters. These results demonstrate that precursor PFAS represent a major and underrecognized component of PFAS flux from engineered water systems and should be incorporated into regulatory monitoring and source control strategies.

Fluorotelomer carboxylic acids (FTCAs) are key intermediates in the environmental transformation of fluorotelomer-based precursors, yet their abiotic degradation pathways remain poorly understood. This study investigates the hydroxide-promoted transformation of n : 2 FTCAs at ambient temperature and under controlled laboratory conditions to elucidate reaction mechanisms and kinetics. Equilibrium experiments were performed across sodium hydroxide (NaOH) concentrations ranging from 1 × 10^-5 to 1 M, revealing transformation onset between 1 × 10^-4 and 2 × 10^-4 M. Both 6 : 2 and 8 : 2 FTCA were fully converted to the corresponding unsaturated products (FTUCAs) at ≥5 × 10^-4 M NaOH, followed by secondary loss of FTUCA at higher base concentrations (>2 × 10^-3 M) to undetected nontarget products. Minor yields (<7%) of perfluorocarboxylic acids (PFCAs) were detected at ≥0.1 M NaOH. Kinetic experiments at 1 × 10^-2 M NaOH showed first-order transformation of 6 : 2 and 8 : 2 FTCA, with observed rate constants (k_obs) of 0.09 and 0.48 h^-1, respectively. When repeated with 0.3% ammonia (NH₃; [OH^-] ∼ 1.74 × 10^-3 M) and 6 : 2 FTCA, the k_obs decreased sixfold (0.015 h^-1) relative to NaOH, consistent with the approximately sixfold lower [OH^-]. Because 0.3% NH₃ is commonly used in PFAS extraction methods, these results suggest that prolonged extractions may lead to underestimation of FTCAs and potentially other precursors. Experiments with a base-containing consumer cleaning product confirmed that this hydroxide-promoted transformation of 6 : 2 FTCA to 6 : 2 FTUCA also occurs in more complex matrices. Mechanistic analysis supports a reversible E1cb pathway in which deprotonation of the α-hydrogen generates a stabilized carbanion intermediate, followed by unimolecular C-F bond cleavage. This study provides the first evidence of abiotic FTCA transformation via an E1cb mechanism and highlights the potential for mild alkaline environments, including those in analytical and household contexts, to promote PFAS precursor transformation.

Pesticides play a critical role in global food security. However, some of them also pose significant environmental and health risks, particularly in tropical regions where data gaps hinder accurate risk assessments. This study compiles and curates properties for 110 pesticide active ingredients commonly used in Cameroon and other tropical African countries, focusing on partitioning between octanol, air, and water (K_OW, K_OA, and K_AW) and between organic carbon and water (K_OC), solubilities in water (S_W) and in octanol (S_O), vapour pressure (V_P), and biodegradation half-lives (HL_biodeg). Empirical data were harmonized using thermodynamic adjustment, and missing properties were predicted using common quantitative structure-activity relationships (QSARs), including Poly-Parameter Linear Free Energy Relationships (PP-LFERs) with empirical Abraham solute descriptors, IFS QSAR, EPI Suite™ and OPERA. Model performance was evaluated against final adjusted empirical values, revealing strong reliability for K_OW and S_W but greater uncertainty for K_AW, K_OA, V_P, and HL_biodeg. Consensus values from multiple models improved prediction performance. The study highlights the scarcity of experimentally derived data for key properties, especially for ionizable and large-molecule pesticides. The study also demonstrates that reactivity parameters like HL_biodeg often play a more influential role compared to partitioning properties in determining the levels of human and ecological exposures, expressed as intake fraction (iF) or Drinking Water Exposure Potential (DWEP). These findings underscore the need for expanded experimental datasets to refine predictive models and support evidence-based pesticide regulation in tropical regions.

Understanding the processes controlling benzene adsorption in soils is critical for predicting their environmental fate and associated risks. However, the adsorption behavior of benzene across different soil components and under varying environmental conditions remains insufficiently understood. In this study, the adsorption thermodynamics of benzene on representative soil components, including humic acid, kaolinite, montmorillonite, birnessite, and goethite, were systematically investigated, combined with the effects of temperature, pH, and coexisting Pb²⁺ ions. Batch adsorption experiments were integrated with machine learning approaches to quantify the adsorption behavior and identify the key controlling factors. The results showed that humic acid exhibited a substantially higher benzene adsorption capacity than the mineral components, with the saturated adsorption capacities at 25 °C following the order of humic acid > birnessite > montmorillonite > goethite > kaolinite. Thermodynamic analysis indicated that benzene adsorption on all components was spontaneous, exothermic, and entropy-decreasing, suggesting a process dominated by physical adsorption. Among the examined environmental factors, temperature exerted a significantly stronger influence on the adsorption equilibrium than pH and coexisting Pb²⁺ ions, with increasing temperatures markedly suppressing benzene adsorption, particularly on humic acid. A machine learning prediction model was constructed using 395 experimental datasets. Among the tested models, the random forest model showed the best predictive performance (R² = 0.97 and RMSE = 1.12 mg g^-1). Feature importance analysis revealed that the initial benzene concentration, specific surface area, micropore volume, and total pore volume were the dominant factors controlling the adsorption, collectively accounting for over 80% of the adsorption behavior. These findings provide process-based insights into soil-benzene interactions and offer a favorable predictive tool for assessing the environmental behavior and remediation potential of benzene-contaminated soils.

The disposal of hazardous materials from Superfund sites often involves thermal treatment (TT), generating environmentally persistent free radicals (EPFRs). While substantial evidence links EPFR exposure to negative health outcomes, its effects on the soil microbiome remain underexplored. Since the mid-1980s, a TT facility in Colfax, LA, has employed open-burn and open-detonation to process hazardous waste. In 2023, we collected soil samples from 13 residential sites within a 17-km radius of the TT facility and analyzed microbial communities and EPFR content. Our findings revealed a distinct microbial community near the TT facility (within 5-km), characterized by reduced bacterial abundance and increased fungal presence. Soil EPFR concentrations ranged from 0.81 × 10¹⁶-4.39 × 10¹⁶ spins per g with g-factor values of 2.0033-2.0040, indicating a mixture of carbon-centered radicals with adjacent oxygen and oxygen-centered radicals. Correlation analysis identified bacterial taxa, particularly Alpha-proteobacteria and Actinobacteria, positively associated with EPFR abundance. In vitro tests showed that laboratory generated EPFRs more strongly inhibited bacterial growth than fungal growth, though some bacterial isolates from the study sites exhibited resistance to EPFR exposure. The differences in microbial responses to EPFR exposure may contribute to the shifts in microbial communities near the TT facility. Our study advances the understanding of EPFR impacts on the soil microbiome and suggests potential long-term effects on environmental and community health.

Marine antifouling paints are often overlooked as a source of microplastic pollution in the aquatic environment even though they may release microplastics and metals, including metallic nanoparticles, into the environment, especially following exposure to environmental stressors. Notably, photodegradation via sunlight and seasonal freeze-thaw cycles are impactful weathering processes that can affect boat hulls in cold climates. In this study, steel coupons coated with marine antifouling paint were submerged in water and exposed to three laboratory-controlled weathering treatments, namely, UV irradiation (UV), freeze-thaw (FT), and UV irradiation combined with freeze-thaw (UV-FT) over 42 days. Water samples were analyzed using optical photothermal infrared spectroscopy (O-PTIR), inductively coupled plasma mass spectrometry (ICP-MS), single particle ICP-MS, and microscopic imaging in order to quantify microplastics, metals and inorganic nanoparticles released from the painted surfaces. Weathering treatments released microplastics through photochemical degradation (UV) and ice abrasion. Meanwhile, for heavy metals, Cu was dominantly released in its microplastic-bound form and Zn in its dissolved form. UV-exposed paint likely underwent oxidative degradation, whereas FT exposure likely caused damage via ice abrasion, resulting in the production of paint microplastics in both cases. The IR and Raman signals showed that paint microplastics generally had high similarity to their respective painted coupons, except for the UV treatment, indicating that paint microplastics can be traced to their original source. Of the three treatments, the combined treatment of UV and FT released the highest concentrations of Cu and Zn over 42 days (49 000 ± 20 000 µg g^-1 and 14 000 ± 7000 µg g^-1, respectively). Cu was released at higher concentrations under weathering conditions that involved abrasion (i.e., UV-FT and FT). In contrast, more Zn was measured in the UV, HC, and CC treatments. Our findings provide a better understanding of the mechanisms leading to the release of paint-derived contaminants into the environment and further highlight the risks posed by the extensive use of marine antifouling paints.

Coal ash disposal poses a significant environmental risk due to the potential leaching of toxic elements into surrounding ecosystems. Here, we analysed the phytotoxic effect of two coal ash disposal sites after 50 years of weathering to evaluate whether coal ash remains toxic after long-term disposal and whether vegetated areas are less toxic than bare ones. To analyse that, a combination of multielement analysis of coal ash and eluates and two bioassays-seed germination and Allium test-was used. Multielement analysis revealed that some samples exceed the World Health Organization's drinking water thresholds; however, biological responses did not consistently align with the total element concentrations. Seed germination was inhibited in 7 out of 12 samples, most strongly in soil and bare ash eluates from both sites. The Allium-based cytogenetic assay showed high mitotic inhibition and genotoxicity in most eluates. Correlation analyses linked Al, As, and V with increased chromosomal aberrations. However, the potential for synergistic or antagonistic interactions among elements complicates the straightforward predictions of toxicity based on concentration alone. Overall, these results advocate for the integration of biological endpoints with chemical data and highlight the persistent toxicity of coal ash even after 50 years of weathering.

Although germanium is increasingly important for modern technologies, its occurrence and biogeochemical behaviour in natural waters remain insufficiently characterized, particularly in freshwater environments; herein, we investigate its speciation and seasonal dynamics in two contrasting drinking water reservoirs. The speciation of dissolved germanium, including inorganic, methyl-, and dimethyl-germanium, was monitored monthly over the course of a year in two drinking water reservoirs. The sampling covered both the productive and winter periods. The study sites were Vrchlice, a eutrophic reservoir in Central Bohemia that becomes anoxic in summer, and Souš, an oligotrophic reservoir in the mountainous region of North Bohemia, which was historically affected by acid rain. Speciation was measured using hydride generation-cryotrapping-inductively coupled plasma-mass spectrometry (HG-CT-ICP-MS/MS). The two reservoirs showed markedly different concentrations of inorganic Ge (iGe). In winter, before snowmelt, iGe concentrations were 3.1 (±0.1) ng L^-1 in Vrchlice and 21.3 (±0.3) ng L^-1 in Souš. Throughout the year, in Vrchlice, iGe developed nutrient-type vertical profiles resembling those of silicon, consistent with the presence of diatoms. In contrast, no such pattern was observed in Souš, where diatoms were absent. Both reservoirs showed evidence of Ge fluxes from sediments during summer. Methylated Ge species exhibited conservative behaviour. In Vrchlice, average concentrations were 0.34 ng L^-1 (±0.04) for methylgermanium and 0.09 ng L^-1 (±0.02) for dimethylgermanium. In Souš, concentrations were lower, with methylgermanium near the limit of quantification at ∼0.07 ng L^-1 and dimethylgermanium below the detection limit. These findings are consistent with earlier observations from Lake Geneva. They confirm that freshwater systems lack an apparent in situ source of methylated Ge species and that the inorganic form dominates, in contrast to marine environments.

Phthalic acid esters (PAEs), commonly used as plasticizers in clothing manufacturing to enhance flexibility and ductility, were investigated in six types of children's intimate apparel. Background concentrations of PAEs in the apparel were first determined, followed by accumulation experiments conducted under controlled indoor conditions after washing. Total PAE background concentrations ranged from 0.655 to 28.0 µg g^-1, with vests, shorts, and socks exhibiting the highest contamination levels. Di (2-ethylhexyl) phthalate (DEHP) and di (2-n-butoxyethyl) phthalate (DBEP) were the most prevalent compounds, with median concentrations of 2.72 µg g^-1 and 1.74 µg g^-1, respectively. Accumulation experiments under low ventilation conditions showed that PAE levels on clothing remained stable over short durations, with no statistically significant temporal variations. Positive Matrix Factorization (PMF) resolved four source factors potentially contributing to clothing contamination, with indoor objects and surfaces being the dominant contributors. Using a clothed child dummy, this study quantified the partition coefficients of PAEs between the gas-phase and clothing, as well as between the gas-phase and dummy skin, under indoor conditions. Results indicated that synthetic fibers promoted PAE accumulation, whereas cotton clothing provided superior, though time-dependent, barrier effects. Higher PAE concentrations on exposed dummy skin confirmed the protective role of clothing.