Environmental Fate Research Articles

Kinetic study, byproducts characterization and photodegradation pathway of profoxydim in a biochar water soil system

The study focused on the photodegradation of profoxydim, a low-toxicity cyclohexanedione herbicide commonly used in rice crops, under simulated sunlight conditions. Profoxydim’s behavior in paddy field conditions is not well understood, and this research aimed to fill that gap, particularly examining the effect of commonly utilized organic amendments such as biochar (BC) on its degradation. Results indicated that profoxydim degrades rapidly, with a half-life of 2.4 ± 0.3 h in paddy water and 1.03 ± 0.1 h in paddy soil. However, when BC was introduced, the degradation slowed significantly, extending the half-lives to 3.1 ± 0.2 h in water and 3.07 ± 0.5 h in soil. The study identified five degradation products (DPs) using TOF mass accuracy measurements and MS/MS spectra fragmentation. Two of these DPs were found to be more stable than profoxydim itself. Additionally, the research proposed a novel photodegradation pathway, highlighting processes such as homolytic C-N bond cleavage, photoisomerization, and photoinduced oxidation. The study’s findings contribute new insights into the environmental fate of profoxydim, offering a deeper understanding of its transformation in rice paddy fields and aiding in the assessment of potential risks associated with its residues in agricultural environments.

The indirect global warming potential of methane oxidation in the IPCC’s sixth assessment report

Abstract Greenhouse-gas emission (GHG) metric values for methane in the sixth assessment report by the Intergovernmental Panel on Climate Change (IPCC) include the indirect effect associated to the oxidation of methane to CO2. An analysis of the figures provided by the IPCC reveals they assume that in average 75% of methane is ultimately oxidized to CO2, while the remaining 25% is converted to intermediate degradation products, most notably formaldehyde, which are removed from the atmosphere via wet and dry deposition and treated by the IPCC as a potential carbon sink in terrestrial and aquatic ecosystems. In this short article we present a critique to this assumption, based on existing knowledge about the environmental fate of methane’s degradation products. We conclude that any assumption other than full degradation of methane to CO2 in a rather short time frame is questionable, whereby the default CO2 yield from this oxidation, as far as GHG metrics are concerned, should be 100%. We re-calculate values for the global warming potential (GWP) metric in accordance with our findings, resulting in an increase in GWP100 from 29.8 and 27.0 to 30.40 and 27.65 kg CO2-equivalents/kg fossil and biogenic methane, respectively. Although we only present the implications in terms GWP, our proposal is conceptually valid for other GHG metrics as well.

Enhanced remediation of acetochlor-contaminated soils using phosphate-modified biochar: Impacts on environmental fate, microbial communities, and plant health

Given that acetochlor (ACT) persists in soil for extended periods, disrupting microbial community structure and causing phytotoxicity to sensitive crops, this study investigated the potential of phosphate-modified biochar (PBC-800) to remediate ACT-contaminated soil. Incorporating 0.5 % PBC-800 into fluvo-aquic, red, and black soils increased their adsorption capacities by 80.4 mg g−1, 76.6 mg g−1, and 76.0 mg g−1, respectively. Even after six months of aging, the Kf values remained 1.6 to 5.1 times higher than in untreated soils. PBC-800 also accelerated ACT degradation across all three soil types, reducing residual ACT levels by 34.3 % to 76.4 % after 60 days, and shortening the degradation half-life by 5 to 7 days. High-throughput sequencing revealed that ACT reduced soil microbial diversity and disrupted community structure, while 0.5 % PBC-800 amendments promoted the growth of degradation-capable genera such as Rhodococcus, Lysobacter, and Gemmatimonas, enhancing microbial ecosystem stability. Furthermore, the amendment of soil with 0.5 % PBC-800 reduced ACT residue concentrations in maize and soybeans by 76.5 % to 82.9 %, and restored plant biomass, leaf chlorophyll content, and mesophyll cell ultrastructure to levels comparable to the control. Therefore, amending ACT-contaminated soil with PBC-800 mitigates ecological and environmental risks, boosts microbial activity, and safeguards plant health.

Photoaging-induced variations in heteroaggregation of nanoplastics and suspended sediments in aquatic environments: a case study on nanopolystyrene

Photoaging of nanoplastics (NPs) and heteroaggregate with suspended sediments (SS) determines transport processes and ecological risks of NPs in aquatic environments. This study investigated the disruption of photoaging on the heteroaggregation behavior of polystyrene NPs (PSNPs) and SS in different valence electrolyte solutions and deduced the interaction mechanisms by integrating aggregation kinetics and molecular dynamics (MD) simulation. Increasing the electrolyte concentration significantly enhanced the heteroaggregation between PSNPs and SS, and the divalent electrolytes induced the heteroaggregation more efficiently. MD simulation at the molecular level revealed that PS and SS could spontaneously form clusters, and photoaged PS has a stronger potential to fold into a dense state with SS. Photoaging for 30 d retarded heteroaggregation due to the steric hindrance produced by the leached organic matter in NaCl solutions, and the critical coagulation concentration (CCC) increased by more than 85.44%. Contrarily, photoaging caused more oxygen-containing functional groups produced on the surface of PSNPs through Ca2+ bridging promoting heteroaggregation and thus destabilizing in CaCl2 solutions, the CCC decreased by 23.53% ∼ 35.29%. These findings provide mechanistic insight into the environmental process of NPs and SS and are crucial for a comprehensive understanding of the environmental fate and transport of NPs in aquatic environments.

Degradation of a novel herbicide fluchloraminopyr in soil: Dissipation kinetics, degradation pathways, transformation products identification and ecotoxicity assessment

With the continuous application of new agricultural chemicals in agricultural systems, it is imperative to study the environmental fate and potential transformation products (TPs) of these chemicals to better assess their ecological and health risks, as well as guide scientific application. The dissipation of fluchloraminopyr was firstly evaluated under aerobic/anaerobic condition in four representative soils, with Dissipation Time 50 (DT50) values ranging from 0.107 to 4.76 days. Eight TPs generated by soil degradation were identified via Ultra-High Performance Liquid Chromatography coupled with Quadrupole Time-of-Flight Mass Spectrometry (UHPLC-QTOF/MS) and Density Functional Theory (DFT) calculations. The predominant transformation reactions of fluchloraminopyr in soil include oxidation, dechlorination, hydroxylation, and acetylation. The predictions from toxicological software indicated that the acute and chronic toxicity of TPs to aquatic organisms was significantly lower than that of fluchloraminopyr. Moreover, both M267 and M221 exhibited higher acute oral toxicity to terrestrial organisms compared to the parent compound. Consequently, these findings offer essential ecological risk evaluation data for the judicious application of fluchloraminopyr.

Global meta-analysis and machine learning reveal the critical role of soil properties in influencing biochar-pesticide interactions

Biochar application in soils is increasingly advocated globally for its dual benefits in enhancing agricultural productivity and sequestering carbon. However, lingering concerns persist regarding its environmental impact, particularly concerning its interactions with pesticide residues in soil. Previous research has fragmentarily indicated elevated pesticide residues and prolonged persistence in biochar-amended soil, suggesting a potential adverse consequence of biochar application on pesticide degradation. Yet, conclusive evidence and conditions for this phenomenon remain elusive. To address this gap, we conducted a comprehensive assessment using meta-analysis and machine learning techniques, synthesizing data from 58 studies comprising 386 observations worldwide. Contrary to initial concerns, our findings revealed no definitive increase in pesticide concentrations in soil following biochar application. Moreover, a significant reduction of 66 % in pesticide concentrations within soil organisms, such as plants and earthworms, was observed. The quantitative analysis identified soil organic matter content as a key factor influencing biochar-pesticide interactions, suggesting that applying biochar to soils rich in organic matter is less likely to increase pesticide persistence. This study provides a critical assessment of the environmental fate of pesticides under biochar application, offering valuable guidance for the optimal utilization of both pesticides and biochar in sustainable agricultural practices.

Performance of Dye-Containing Wastewater Treatment Using MnxOy-Catalyzed Persulfate Oxidation

Dye wastewater is characterized by high salinity, intense coloration, difficulty in degradation, and complex organic compositions, posing significant environmental risks. Manganese oxide (MnxOy)-based materials have been widely used for the removal of recalcitrant organic pollutants in water environments. In this study, various MnxOy polymorphs were prepared, and their catalytic activities for persulfate (PS) activation were evaluated using Orange II (AO7) as a model molecule. After 50 min treatment, the degradation efficiency of AO7 ranked as α-MnO2/PS > γ-MnO2/PS > β-MnO2/PS > Mn2O3/PS, with α-MnO2/PS achieving the highest efficiency of 98.6%. XPS, XRD, and electrochemical analyses indicated that α-MnO2 exhibited an exceptional crystal structure and performance. The α-MnO2/PS system exhibited a strong pH adaptability across a wide pH range of 3.0–9.0. The presence of coexisting anions at 0.1 mM, including Cl−, NO3−, CO32−, and SO42−, slightly reduced the degradation rate of AO7. The reactive oxygen species, mainly SO4•− and 1O2, predominantly destroyed the naphthalene ring structure of AO7. Furthermore, α-MnO2 exhibited an excellent stability, allowing for multiple reuse cycles without interference from common anions in water, highlighting its strong potential for practical applications. These results provided insights into the environmental fates of AO7 in the α-MnO2/PS system.

The Impact of Metal Ions on MXene Membranes: Critical Role of Titanium Vacancies.

Two-dimensional transition metal carbides and nitrides (MXenes) and MXene-based membranes hold promise for applications including water purification and seawater desalination; however, their environmental behavior and fate in these matrices remain unknown. In this study, we systematically assessed the reaction efficiencies of Ti3C2Tx at varying important environmental conditions. Our experiments revealed that copper and iron ions accelerated the oxidation rate of Ti3C2Tx 55.4 and 33.4 times, respectively. TiO2 and amorphous carbon were identified as the primary solid products. Based on in situ water-phase atomic force microscopy, atomic high-angle annular dark-field scanning transmission electron microscopy, and theoretical results, we postulate that metal ions enhance Ti3C2Tx oxidation by spontaneously migrating and anchoring at Ti vacancies, which then become active sites for this reaction. This process increases the adsorption of H2O and oxygen, making the Ti vacancy-rich surface convex area the most vulnerable site to attack. The findings in this study provide useful information for a comprehensive understanding of the interaction between MXene structural defects and metal ions as well as for the design and modification of MXene membranes resistant to metal ion impact.

Transport behavior of Polymeric Methyl Methacrylate nanoplastics in saturated and unsaturated porous media: Combined influence of electrolyte and organic acids

The migration behavior of Polymeric Methyl Methacrylate (PMMA) nanoplastics in saturated porous media and unsaturated porous media is investigated under conditions of electrolytes in combination with organic acids. In the saturated porous media, the mass recovery rate of PMMA decreases with ionic strength. The inhibition effect of Ca2+ on PMMA transport is stronger than that of Na+. Under the conditions of the coexistence of electrolytes with humic acid (HA), increasing the concentration of HA does not consistently enhance PMMA migration in porous media. However, citric acid (CA) exerts solely an inhibitory effect on PMMA transport. The orthogonal analysis suggests that Ca2+ concentration is the major factor affecting PMMA transport. Extended Darjaguin-Landau-Verwe-Overbeek (XDLVO) interaction energy considering the heterogeneity of HA adsorption on PMMA is calculated to quantify the interactions of PMMA-PMMA and PMMA-quartz sand under different physiochemical conditions. In unsaturated porous media, gravity leads to the creation of dominant channels, and the shear force of water flow in porous media leads to the rapid passage of PMMA through the dominant channels. However, as the water content decreases, the recovery rate of PMMA decreases from 0.99 to 0.71. Significantly, the capillary energy of a colloid retained in a thin film or at the air-water-solid (AWS) interface is several orders of magnitude larger than the XDLVO interaction energy. Findings obtained by this study may improve the current understanding of the environmental fate of nanoplastics in subsurface environments and can provide scientific methods to assess the associated risk of nanoplastics.

Identification, characterization, and distribution of novel amidase gene aphA in sphingomonads conferring resistance to amphenicol antibiotics.

Amphenicol antibiotics, such as chloramphenicol (CHL), thiamphenicol (TAP), and florfenicol (Ff), are high-risk emerging pollutants. Their extensive usage in aquaculture, livestock, and poultry farming has led to an increase in bacterial antibiotic resistance and facilitated the spread of resistance genes. Yet, limited research has been conducted on the co-resistance of CHL, TAP, and Ff. Herein, a novel amidase AphA was identified from a pure cultured strain that can concurrently mediate the hydrolytic inactivation of CHL, TAP, and Ff, yielding products p-nitrophenylserinol, thiamphenicol amine (TAP-amine), and florfenicol amine (Ff-amine), respectively. The antibacterial activity of these antibiotic hydrolysates exhibited a significant reduction or complete loss in comparison to the parent compounds. Notably, AphA shared less than 26% amino acid sequence identity with previously reported enzymes and exhibited high conservation within the sphingomonad species. Through enzymatic kinetic analysis, the AphA exhibited markedly superior affinity and catalytic activity toward Ff in comparison to CHL and TAP. Site-directed mutagenesis analysis revealed the indispensability of catalytic triad residues, particularly serine 153 and histidine 277, in forming crucial hydrogen bonds essential for AphA's hydrolytic activity. Comparative genomic analysis showed that aphA genes in some species are closely adjacent to various transposable elements, indicating that there is a high potential risk of horizontal gene transfer (HGT). This study established a hydrolysis resistance mechanism of amphenicol antibiotics in sphingomonads, which offers theoretical guidance and a novel marker gene for assessing the prevalent risk of amphenicol antibiotics in the environment.IMPORTANCEAmphenicol antibiotics are pervasive emerging contaminants that present a substantial threat to ecological systems. Few studies have elucidated resistance genes or mechanisms that can act on CHL, TAP, and Ff simultaneously. The results of this study fill this knowledge gap and identify a novel amidase AphA from the bacterium Sphingobium yanoikuyae B1, which mediates three typical amphenicol antibiotic inactivation, and the molecular mechanism is elucidated. The diverse types of transposable elements were identified in the flanking regions of the aphA gene, indicating the risk of horizontal transfer of this antibiotic resistance genes (ARG). These findings offer new insights into the bacterial resistance to amphenicol antibiotics. The gene reported herein can be utilized as a novel genetic diagnostic marker for monitoring the environmental fate of amphenicol antibiotics, thereby enriching risk assessment efforts within the context of antibiotic resistance.

Subjectivity of visual assessments in FOCUS kinetics and acceptability of first-order fits for regulatory modelling

The degradation half-life (DegT50) of a substance in soil plays an important role in the approval process of a plant protection product and is a sensitive input parameter for regulatory models. It is usually derived through least squares optimizations of mathematical models to measured degradation data according to EU FOCUS degradation kinetics guidance. A strong consensus on degradation parameters provides a solid foundation for parts of the environmental risk assessment. The DegT50 of a substance for regulatory modeling is preferably derived from a single first-order (SFO) model as this is currently the only kinetic model implemented in EU regulatory models of the environmental fate of pesticides. However, kinetic optimisation tools do not always provide a regulatory acceptable SFO fit even though a visual inspection of the data suggests it may be possible. It was therefore hypothesized that more acceptable SFO fits might be achieved by adapting the objective function that is minimized during the optimization.Eight objective functions with varying weightings were tested on 29 laboratory soil degradation datasets. A web-based app was developed to allow experts in environmental safety of plant protection products to visually assess the goodness of fits resulting from different objective functions. The visual assessments and a quantitative metric, newly introduced in the proposed update of the FOCUS guidance, show that the acceptability of SFO fits can be increased, but no single objective function exclusively improves all fits. The assessment reveals that expert judgment is very subjective. Participants tended to change their mind when judging the acceptance of a fit, assumingly caused by a learning curve or a period of calibration.It is concluded that different objective functions could be considered in the kinetic assessment as it can improve the acceptability of SFO fits and hence endpoints for regulatory modeling. This study reveals that various qualitative factors influence the visual judgment of experts when performing a kinetic modeling assessment. The proposed quantitative metric seems to be in alignment with the visual assessment of fits to derive modeling endpoints and a promising step toward less subjective kinetic modeling assessments.

Anaerobic Degradation of Aromatic and Aliphatic Biodegradable Plastics: Potential Mechanisms and Pathways.

Biodegradable plastics (BDPs) have been widely used as substitutes for traditional plastics, and their environmental fate is a subject of intense research interest. Compared with the aerobic degradation of BDPs, their biodegradability under anaerobic conditions in environmental engineering systems remains poorly understood. This study aimed to investigate the degradability of BDPs composed of poly(butylene adipate-co-terephthalate) (PBAT), poly(lactide acid) (PLA), and their blends, and explore the mechanism underlying their microbial degradation under conditions of anaerobic digestion (AD). The BDPs readily depolymerized under thermophilic conditions but were hydrolyzed at a slow rate under conditions of mesophilic AD. After 45 days of thermophilic AD, a decrease in the molecular weight and significant increase in the production of methane and carbon dioxide production were observed. Network and metagenomics analyses identified AD as reservoirs of plastic-degrading bacteria that produce multiple plastic-degrading enzymes. PETase was identified as the most abundant plastic-degrading enzyme. A potential pathway for the anaerobic biodegradation of BDPs was proposed herein. The polymers of high molecular weight were subjected to abiotic hydrolysis to form oligomers and monomers, enabling subsequent microbial hydrolysis and acetogenesis. Ultimately, complete degradation was achieved predominantly via the pathway involved in the conversion of acetic acid to methane. These findings provide novel insight into the mechanism underlying the anaerobic degradation of BDPs and the microbial resources crucial for the efficient degradation of BDPs.

Shift from legacy to emerging per- and polyfluoroalkyl substances for watershed management along the coast of China

Per- and polyfluoroalkyl substances and their short-chain alternatives have attracted world-wide attention due to their widespread presence and persistence in the environment. However, the sources, environmental fate, and driving forces of PFAS in coastal ecosystems remain poorly understood. In this study, the spatial distribution, source apportionment, and driving mechanisms of PFAS were investigated through a comprehensive analysis of water samples collected along the China's coastline. The concentrations of Σ25PFAS in water samples followed a general pattern, with higher levels observed in northern coastal zones of China than the south, ranging from 0.72 to 1872.21 ng L−1. PFOA and PFBA were dominant. Emerging short-chain PFAS, such as PFBS, PFBA, F-53B and GenX, were frequently detected, with detection rates of 97%, 99%, 95% and 77%, respectively. This indicated a shift in coastal PFAS contamination from legacy compounds to emerging short-chain alternatives. Source apportionment using the Positive Matrix Factorization model identified key contributors to PFAS pollution, including textile production, volatile precursors, precious metal industries, aqueous film-forming foam, metal-plating, electrochemical fluorination, and fluoropolymer manufacturing. Additionally, PFAS concentrations were significantly positively correlated with cultivated land, urban area, and wastewater discharge, while negatively correlated with annual precipitation and woodland coverage (p < 0.05). Socio-economic development was identified as a major driver of PFAS emissions, while the hydrological factors and vegetation coverage can significantly enhance watershed resilience against PFAS pollution.

Environmental Degradation Study of Polypropylene Films Incorporating Pro-Oxidants: Comprehensive Analysis and Ecotoxicological Assessment

Our research described in this paper investigated the environmental degradation of polypropylene (PP) films incorporating pro-oxidants and assessed their impact on the ecosystem. Weathering aging effects were monitored through Fourier-Transform Infrared (FTIR) analysis, revealing significant changes in carbonyl, hydroxyl and amorphous regions post-aging. The presence of pro-oxidants intensified these changes, indicating higher oxidation levels. Contact angle measurements demonstrated decreased hydrophobicity upon aging, particularly pronounced in pro-oxidant-containing films (initial contact angle: 87.79° for PP/1% Co/1% Fe, sample (F6) decreased to 79.24° after aging). Differential Scanning Calorimetric (DSC) analysis revealed decreased melting temperatures (initial Tm: 159.5 °C for F6 decreased to 148 °C after aging) and the crystallinity post-aging (initial χ: 73.25% for F6 decreased to 60.17% after aging), suggesting increased susceptibility to degradation. Thermogravimetric Analysis (TGA) showed decreased thermal stability after aging, especially in PP/pro-oxidant films; the Tonset (T5); 432.00 °C for F6, decreased to 268.00 °C after aging; where Tonset is the temperature corresponding to 5% weight loss. Biodegradation tests indicated enhanced biodegradability in the pro-oxidant-containing films, with cobalt and ferrous stearate mixtures showing the highest degradation degrees (e.g., PP/1% Co/1% Fe: ≈ 77% biodegradation after 140 days). Ecotoxicological evaluations, including microbial toxicity and plant germination and growth tests, revealed no inhibitory effects of the degradation products on soil flora or plant growth, confirming their nontoxic nature. Overall, we believe this comprehensive study provides insights into the environmental fate of PP films with pro-oxidants, highlighting their potential for accelerated degradation without adverse ecological impacts.

The soil-air interfacial migration process of volatile PFAS at the contaminated sites: Evidence from stable carbon isotopes with CSIA

Volatile per- and polyfluoroalkyl substances (PFAS) are prone to transport among various environmental media, with the soil-air interfacial migration process being an important pathway that significantly influences their environmental fate. To assess the migration and transformations of target volatile PFAS at contaminated site using compound-specific stable isotope analysis (CSIA), it is necessary to understand the isotopic fractionation that occurs during their transfer from soil to air. We have established methods for pre-treatment and GC/CSIA analysis methods of target volatile PFAS in soil and air samples and ensured the accuracy of carbon isotope analysis. GC/IRMS δ13C measurements showed optimal precision at instrumental response above 1.35–2.75 Vs, with recommended minimum on-column C levels of 1.67–5.00 nmol for target volatile PFAS. Stable carbon isotope fractionation factors related to the soil-air interfacial migration process for target volatile PFAS were determined by performing laboratory simulations. The observed εsoil-air values are all negative, suggesting that the soil-air interfacial migration process for target volatile PFAS is kinetic fractionation, the removal of molecules containing lighter isotopes. By comparing the simulated and experimentally observed δ13C (‰) values of target volatile PFAS, we found consistent trends in the soil and inverse trends in the air. These δ13C (‰) values and the related isotope fractionation model provide valuable insights into the isotopic behavior of target volatile PFAS during soil-air interfacial migration process, aiding in the assessment of their environmental fate.

Real-Time Visualization of Infiltration and Retention of Microplastics with Different Shapes in Porous Media.

Infiltration and retention of microplastics in porous media are important for understanding their fate in environments and formulating treatment measures. Given porous media opacity, knowledge is usually obtained indirectly by monitoring microplastic concentration in the effluent and measuring microplastic distribution after removing grains in layers. In this study, real-time visualization of infiltration and retention of microplastics in porous media under vertical water flow is performed using an improved reflective index matching method, considering the different shapes and densities of microplastics and size ratios between microplastics and grains. The spherical microplastics have the largest infiltration depths, with trajectories closest to vertical and accompanied by long acceleration durations and low deceleration frequencies. The cylindrical microplastics deviate from vertical and have stronger transverse oscillations and more frequent decelerations, while the flaky microplastics have the most significant transverse displacements. The infiltration depth can be improved by reducing the size ratio between microplastics and grains and increasing the vertical flow rate, while the density of microplastics has a relatively limited effect. Sliding and rotating of microplastics after collision with grains are observed, responsible for deceleration and transverse displacements. Different retention patterns are found, with the number of types being inversely proportional to the number of principal dimensions of the shape.

Unveiling Priority Emerging PFAS in Taihu Lake Using Integrated Nontarget Screening, Target Analysis, and Risk Characterization.

Amidst tightening regulations, the proliferation of next-generation per- and polyfluoroalkyl substances (PFAS) necessitates a deeper understanding of their environmental fate and potential risks. Here, we conducted a comprehensive assessment of PFAS in the water and sediment of Taihu Lake, incorporating both nontarget and target screening, seasonal and geographical variation analysis, and risk prioritization. A total of 58 PFAS from 13 classes were identified, revealing complex PFAS contamination. In addition to short-chain perfluoroalkyl carboxylates (PFCAs) and sulfonates (PFSAs), bis(trifluoromethanesulfonyl)imide (Ntf2) and perfluoro-2,5-dimethyl-3,6-dioxo-heptanoic acid (C7 HFPO-TA) exhibited relatively high concentrations in water, with median values of 21.7 and 5.72 ng/L, respectively. Seasonal and geographical variation analysis revealed elevated levels of C7 HFPO-TA, Ntf2, and perfluorohexanoic acid (PFHxA) in the northeastern areas, suggesting transport via water diversion project. Multicriteria risk prioritization identified four high priority PFAS (Ntf2, C7 HFPO-TA, PFHxA, and perfluorooctanoic acid (PFOA)) in water and two high priority PFAS (hexafluoropropylene oxide dimer acid (HFPO-DA) and PFHxA) in sediment. Overall, this study revealed Ntf2 and C7 HFPO-TA as priority PFAS in Taihu Lake, underscoring the urgent necessity of evaluating risks associated with these emerging PFAS.

Understanding the environmental fate and removal strategies of phenylurea herbicides: A comprehensive review

Phenylurea herbicides have long been utilized in agricultural practices for their efficacy in weed control. They play a significant role in modern agriculture, aiding in crop protection. However, their extensive use raises concerns about their environmental fate and potential adverse impacts on ecosystems thus prompting extensive research into their fate and removal strategies. This comprehensive review explores the environmental fate of phenylurea herbicides, focusing on their persistence, mobility, and bioavailability. Furthermore, the ecological consequences of their presence, such as effects on non-target organisms and potential for bioaccumulation, have also been analysed. The review also provides an in-depth analysis of removal strategies, encompassing physical, chemical, and biological methods, highlighting their effectiveness and limitations. The present study offers insights into successful applications and challenges encountered in removing phenylurea herbicides from environmental matrices. This review serves as a valuable resource for researchers, policymakers, and environmental practitioners seeking a comprehensive understanding of phenylurea herbicides' and addressing the environmental risks associated with them, guiding efforts toward their safe and effective use while preserving environmental quality and biodiversity.

Atmospheric Chemistry of Chloroprene Initiated by OH Radicals: Combined Ab Initio/DFT Calculations and Kinetics Analysis.

Chloroprene (CP; CH2═C(Cl)-CH═CH2) is a significant toxic airborne pollutant, often originating from anthropogenic activities. However, the environmental fate of CP is incompletely understood. High level CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ calculations combined with kinetic modeling were employed here to glean new insight into the reaction mechanism, energies, and kinetics of the reaction of CP with OH radical (•OH). We report the energies of four different addition pathways and six different abstraction pathways. The •OH attack on the terminal C1 atom of the =CH2 group (which is directly attached to the =CCl moiety), leading to the formation of HOCH2-•C(Cl)-CH═CH2, was found to be a major path. The barrier height for the formation of the corresponding transition state was found to be -1.9 kcal mol-1 below that of the starting CP + •OH reactants. Rate coefficients were calculated for addition and abstraction pathways involving the CP + •OH reaction under pre-equilibrium approximation conditions, employing a combination of canonical variational transition state theory and small curvature tunneling. The overall rate coefficient for the reaction of CP + •OH at 298 K was found to be 1.4 × 10-10 cm3 molecule-1 s-1. The thermochemistry of the possible channels and atmospheric implications are provided. In addition, the fate of HOCH2-•C(Cl)-CH═CH2 in the presence of 3O2 was investigated. We found the reaction of the CP-derived peroxy radical adduct with HO2 and NO to make contributions to the formation of products such as formaldehyde, HO2 radical, Cl atom, HOCH2C(OOH)(Cl)CH═CH2, HOCH2C(O)Cl, ClC(O)CH═CH2, HOCH2C(O)CH═CH2, and HC(O) radical.

Aged Microplastics and Antibiotic Resistance Genes: A Review of Aging Effects on Their Interactions.

Background: Microplastic aging affects the dynamics of antibiotic resistance genes (ARGs) on microplastics, yet no review presents the effects of microplastic aging on the associated ARGs. Objectives: This review, therefore, aims to discuss the effects of different types of microplastic aging, as well as the other pollutants on or around microplastics and the chemicals leached from microplastics, on the associated ARGs. Results: It highlights that microplastic photoaging generally results in higher sorption of antibiotics and ARGs due to increased microplastic surface area and functional group changes. Photoaging produces reactive oxygen species, facilitating ARG transfer by increasing bacterial cell membrane permeability. Reactive oxygen species can interact with biofilms, suggesting combined effects of microplastic aging on ARGs. The effects of mechanical aging were deduced from studies showing larger microplastics anchoring more ARGs due to rough surfaces. Smaller microplastics from aging penetrate deeper and smaller places and transport ARGs to these places. High temperatures are likely to reduce biofilm mass and ARGs, but the variation of ARGs on microplastics subjected to thermal aging remains unknown due to limited studies. Biotic aging results in biofilm formation on microplastics, and biofilms, often with unique microbial structures, invariably enrich ARGs. Higher oxidative stress promotes ARG transfer in the biofilms due to higher cell membrane permeability. Other environmental pollutants, particularly heavy metals, antibacterial, chlorination by-products, and other functional genes, could increase microplastic-associated ARGs, as do microplastic additives like phthalates and bisphenols. Conclusions: This review provides insights into the environmental fate of co-existing microplastics and ARGs under the influences of aging. Further studies could examine the effects of mechanical and thermal MP aging on their interactions with ARGs.