Environmental Science & Technology Letters Environ.最新文献

Perfluorooctanoic acid (PFOA) is a PFAS compound of significant concern due to its persistence and adverse health effects. Effective treatment techniques for highly concentrated PFOA solutions are needed to curb elevated emissions from industrial fluorochemical manufacturing sites among other treatment/waste streams. Herein, we report that in the presence of decanol alone, PFOA readily transforms into a stable fluorinated ester (decylpentadecafluorooctanoate), which precipitates out of solution due to a significant decrease in solubility. The mixture of PFOA and decanol, without additional surfactant, is sufficient for formation of nonaqueous phase emulsions wherein esterification proceeds at 90% yield near room temperature. Reaction kinetics, mass balance, and products are detailed, via FTIR and ¹⁹F qNMR, for a range of conditions. Taken together, this reaction opens a potential new treatment paradigm for concentrated, carboxylic-based PFAS, via a low-energy, green chemistry-based approach.

A network meta-analysis (NMA) was conducted to explore associations between fluorotelomer alcohol (FTOH) transformation and factors affecting perfluoroalkyl carboxylate (PFCA) evolution in synthetic and environmental media. Data were extracted from a total of 14 primary research articles aligned with bench-scale investigations into 6:2 and/or 8:2 FTOH biotransformation; these data were subjected to a random effect NMA to simultaneously evaluate influences of various experimental conditions on biotransformation. Effectiveness rankings were used to summarize experimental conditions promoting FTOH to PFCA transformation from the greatest to least effect on conversion. Results related to atmospheric conditions and/or electron accepting processes (from greatest to least effect on PFCA formation) are as follows: aerobic, nitrate reducing conditions, microoxic, anaerobic (unamended electron acceptor [EA]), sulfate reducing conditions, and iron reducing conditions. A greater association with PFCA formation was observed under mesophilic conditions compared to psychrophilic conditions. Multiple conditions that promote FTOH to PFCA bioconversion in environmental matrices were identified in this study. Several conditions under which transformation is unlikely have also been identified, suggesting the possibility of long-term FTOH retention in impacted media with limited short- and long-chain PFCA mobilization. Our findings further suggest the need for advancing our understanding of FTOH transformation in media receiving excessive nitrogen from anthropogenic sources.

N,N′-Substituted p-phenylenediamines (PPDs) are widely utilized as rubber antioxidants and emitted into the environment with their transformation products (TPs) including the highly toxic 6PPD-quinone. However, the occurrence of PPDs and TPs in inconspicuous rubber products and their oxidation kinetics under natural aging conditions remains unclear. Herein, we performed a field survey of these compounds in crumb rubbers from 40 school artificial turfs. Twelve PPDs and TPs were frequently detected in rubber particles, dominated by the well-known N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) and N-isopropyl-N′-phenyl-1,4-phenylenediamine (IPPD), as well as their PPD-Qs. One pristine rubber material was chosen to simulate the aging process and examine the oxidation kinetics. The concentrations of all antioxidants in rubber powder decreased > 50% within 4 days under natural aging, much faster than that in particles, suggesting the size effect on oxidation. Different PPDs had distinct oxidation degrees under both field and simulated experiments. Besides ozone, we found that high temperature could induce a significantly faster decay of PPDs within rubber particles than UV exposure. In sum, our field and simulated investigations reveal that the transformation of PPDs to PPD-Qs is ubiquitous and chemically specific in artificial turf, which could be affected by particle size and temperature as key factors in controlling oxidation kinetics.

Particulate matter (PM) emitted from road traffic causes adverse health effects upon inhalation and respiratory deposition. Non-exhaust emissions will eventually become the dominant source of traffic PM upon transition to electric vehicles; however, non-tailpipe PM is currently unregulated as its health impacts are still unclear. In this study, we generated brake wear particles (BWPs) with non-asbestos organic, ceramic, and semimetallic brake pads using custom dynamometers and measured aqueous-phase formation of reactive oxygen species (ROS). We found that BWPs do not contain environmentally persistent free radicals (EPFRs), and all types of BWPs generate exclusively ·OH radicals in water. BWPs generated by ceramic and semimetallic brakes during heavier braking lead to higher ·OH yields compared to gentle braking conditions, suggesting higher ·OH formation potential from ultrafine BWPs. Chemical characterization reveals that organic and elemental carbon correlated positively with ·OH formation while exhibiting negative correlations with abundant metals including Fe and Mn. We suggest that the source of ·OH is thermal decomposition of organic hydroperoxides derived from phenolic resin. PM oxidative potential quantified with the dithiothreitol (DTT) assay exhibited a positive correlation with the ·OH yield. These results provide critical insights into the toxicity and adverse health effects of BWPs.

The nonextractable residues (NER) of halogenated organic chemicals (HOC), a crucial yet underexplored component in field soil/sediment monitoring, have traditionally been overshadowed by analyses focusing solely on the solvent extractable fraction (EF). This has led to NER-HOC becoming an invisible “analytical iceberg”, with their compositions, levels, and potential risks obscure. Building on our prior research, which revealed distinct distributions of EF-HOC and NER-HOC in industrialized urban and remote permafrost soils, we expanded our study to include suburban soils from both a megacity and a smaller city. Employing solvent extraction and alkaline hydrolysis, we were able to analyze both EF-HOC and NER-HOC. Our findings showed an increased NER-HOC to EF-HOC ratio and a higher prevalence of metabolite HOC compared to parent HOC in areas with reduced anthropogenic impacts. Notably, except for the soils from a point source site, all other locations exhibited NER to EF ratios exceeding 1, indicating a dominance of NER in these HOC pools. This highlights the potential importance for incorporating NER-HOC analysis in soil/sediment monitoring, especially in nonpoint source and remote locations. Our findings contribute to the understanding of the HOC distribution from diverse sources in varying environmental settings and suggest broader NER-HOC analyses in environmental assessments.

Per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in the environment, raising concerns about human exposure. The assessment of individual exposure to PFAS has been limited due to the lack of specialized sampling tools. Personal wearable samplers, including silicone wristbands, have been used for PFAS exposure assessment. However, translating data into human exposure has been challenging due to the lack of chemical sampling rates by those samplers. We developed and evaluated a personal air wearable sampler (PAWS) using sorbent-impregnated polyurethane foam for its ability to capture diverse PFAS. Simultaneously, we deployed silicone wristbands for comparison. Our results showed that the PAWS effectively captured both ionic and neutral PFAS, while silicone wristbands had relatively limited capacity for perfluorocarboxylic acids (PFCAs). Our observations suggest silicone wristbands may collect polyfluoroalkyl phosphoric acid diesters (diPAPs) through dermal contact, although further investigation is necessary. PFAS concentrations detected in the PAWS can be converted into concentrations in air by using previously established sampling rates, facilitating quantitative inhalation exposure assessment. Smoking status was found to be associated with high diPAP levels in both PAWS and silicone wristbands, although further validation is needed. The PAWS is a promising technology for application in personal exposure assessment for structurally diverse chemicals.

Hydrogels possess a strong water absorption capability and can release absorbed water in response to physical or chemical stimuli, making them promising materials for water recycling. To explore the concept of using hydrogels to recover water from wastewater, we synthesized and utilized poly(acrylic acid-co-acrylamide) (PAAM) hydrogels to extract water from solutions containing various organic pollutants and salt concentrations. The swelling ratio of PAAM hydrogels reached up to 510 g/g with a water recovery of around 44% and a water production rate of approximately 3200 L/kg/day. The removal rates of organic pollutants reached up to 89%, depending on the pollutant’s properties such as molecular weight, functional group, solubility, and charge. This confirms the potential of using hydrogels to recover water from various wastewaters, especially for those containing large molecular pollutants.

Limited by the detection techniques, the reactive species involved in catalytic water purification processes are difficult to be clarified. Spin-trapping electron paramagnetic resonance (EPR) analysis is recognized as a reliable tool for radical identification, in which 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) is usually used as the radical trapper. However, it is questioned that the detection of adducts of DMPO definitively indicates the generation of radicals. In this work, the DMPO transformation caused by transition metal oxides is monitored by EPR, and abundant spin signals are observed. MnO₂, Mn₂O₃, and NiO could oxidize DMPO into DMPOX through direct oxygen transfer. Besides, the dissolved transition metal ions could transform DMPO into misleading DMPO–OH and DMPO–R. The findings in this work, e.g., the interactions between DMPO and different metal oxides and the quenching behavior of the different pathways, would help with reliable identifications of reactive species in both engineered systems and natural environments.