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The widespread occurrence of N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q) in aquatic environments and its hazards to aquatic species underscore the necessity of comprehending its environmental fate. Here, we investigated the transformation from 6PPD to 6PPD-Q and the attenuation of 6PPD-Q in surface water under natural conditions. Contrary to prior findings, this work revealed that 6PPD-Q and its precursor 6PPD-OH/6PPD-(OH)2, were not detected through target analysis and suspect screening during 6PPD transformation in the surface water under the natural conditions. 6PPD-Q predominantly accumulated in TWPs in ambient atmosphere with 1.28 % mass yield from the 6PPD dissipation. Subsequently, 6PPD-Q was eluted from TWPs and released to the water environment. The investigation on the natural attenuation of 6PPD-Q in the surface water demonstrated that direct and indirect photolysis facilitated the rapid dissipation of 6PPD-Q with a half-life of 2.57 h. Utilizing the liquid chromatography high resolution mass spectrometry (LC-HRMS), including both time of flight (TOF) MS and Orbitrap MS, twelve novel transformation products (TPs) of 6PPD-Q were identified by using a comprehensive non-targeted screening strategy. The results from two dimensions gas chromatography (GC×GC) TOF-MS revealed additional two TPs. Based on the molecular structure of TPs, four major pathways of 6PPD-Q attenuation were proposed, including bond cleavage, hydroxylation, quinone cleavage and rearrangement. All TPs were predicted to exhibit lower toxicity, indicating the natural attenuation of 6PPD-Q reduced its toxicity and potential environmental risks. This study provides crucial insights into the environmental fate of 6PPD-Q, highlighting the significance of understanding both its formation from 6PPD and its subsequent attenuation processes under natural conditions.

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The degradation of isopyrazam in soils was investigated through kinetics, microbial contributions, and transformation products (TPs). Then the acute toxicity of isopyrazam and its TP to Chlorella pyrenoidosa was explored. The half-lives of isopyrazam in cinnamon soil, red soil, and black soil were 82.2, 141.7, and 120.3 days, respectively. A strain (Bacillus sp. A01) isolated from cinnamon soil could degrade 72.9% of isopyrazam at 10 mg/L after 6 days in a Luria-Bertani medium. Six TPs were observed with Bacillus sp. A01, and three of them were found in soil as well. Through the inhibition of cytochrome P450 enzymes, the production of oxidized isopyrazam was blocked. Microbial mediated hydroxylation, epoxidation, and dehydration were the main degradation pathways of isopyrazam. The acute toxicity results showed that the EC50 of 3-(difluoromethyl)-N-(9-(2-hydroxypropan-2-yl)-1,2,3,4-tetrahydro-1,4-methanonaphthalen-6-yl)-1-methyl-1H-pyrazole-4-carboxamide to Chlorella pyrenoidosa was 40 times higher than that of the parent. This work provides new insights for understanding the degradation behavior of isopyrazam in soil.

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The release of rubber-derived chemicals (RDCs) in road surface runoff has received significant attention. Urban surface runoff is often the confluence of stormwater runoff from specific areas. However, the impact of precipitation on RDCs contamination in confluent stormwater runoff and receiving watersheds remains poorly understood. Herein, we investigated the profiles of RDCs and their transformation products in confluent stormwater runoff and receiving rivers affected by precipitation events. The results showed that 34 RDCs are ubiquitously present in confluent stormwater runoff and surface water, with mean concentrations of 1.03-2749 and 0.28-436 ng/L, respectively. The most dominant target compounds in each category were N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), 6PPD-quinone, 2-benzothiazolol, and 1,3-diphenylguanidine. Total RDCs concentrations in confluent stormwater runoff decreased spatially from industrial areas to business districts to college towns. A significant decrease in RDCs levels in surface water after rainfall was observed (P < 0.01), indicating that precipitation contributes to alleviating RDCs pollution in receiving watersheds. To our knowledge, this is the first report of N,N'-ditolyl-p-phenylenediamine quinone (DTPD-Q) levels in surface waters in China. The annual mass load of ∑RDCs reached 72,818 kg/y in confluent stormwater runoff, while 38,799 kg/y in surface water. The monitoring of confluent stormwater runoff is an efficient measure for predicting contamination loads from RDCs in rivers. Risk assessment suggested that most RDCs posed at least medium risks to aquatic organisms, especially 6PPD-quinone. The findings help to understand the environmental fate and risks of RDCs in the confluent stormwater runoff and receiving environments after precipitation events.

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Unsymmetrical dimethylhydrazine (UDMH) based rocket fuel, when released into the soil, undergoes oxidative transformations to form a variety of toxic nitrogen-containing products (TPs). Loamy soils containing aluminosilicates (clay) are capable of strong binding and retention of UDMH TPs due to a combination of polar sorption and cation-exchange properties, posing challenges for their extraction and quantification. To overcome this problem, the present study proposes direct thermal desorption (TD) of analytes from loam facilitated by the addition of modifiers competing with UDMH TPs for sorption centers and ensuring their conversion into molecular form. Among tested additives, the mixture of potassium chloride and hydroxide demonstrated the best performance and provided recoveries of the most UDMH TPs exceeding 70% under optimized TD conditions (200°C, 30 min). The online combination of TD with gas chromatography-tandem mass spectrometry allowed for the development of a method for the determination of 15 UDMH TPs in loamy soils with limits of detection in the range of 0.2-15 µg/kg. The use of matrix-matched calibration and deuterated internal standards ensured high accuracy (80%-100%) and precision (relative standard deviation < 18%) of the analysis. The developed method was validated and successfully tested in the analyses of real loamy soil samples polluted with rocket fuel.

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As new pesticides continue to emerge in agricultural systems, understanding their environmental behavior is crucial for effective risk assessment. Tiafenacil (TFA), a promising novel pyrimidinedione herbicide, was the focus of this study. We developed an efficient QuEChERS-UHPLC-QTOF-MS/MS method to measure TFA and its transformation products (TP1, TP2, TP3, TP4, and TP5) in soil. Our calibration curves exhibited strong linearity (R2 ≥ 0.9949) ranging from 0.015 to 2.0 mg/kg within a low limit of quantification (LOQ) of 2.0 µg/kg. Inter-day and intra-day recoveries (0.10 to 2.0 mg/kg, 80.59% to 110.05%, RSD from 0.28% to 12.93%) demonstrated high sensitivity and accuracy. Additionally, TFA dissipation under aerobic conditions followed first-order kinetics, mainly yielding TP1 and TP4. In contrast, TP1 and TP2 were mainly found under sterilized and anaerobic conditions, and TFA dissipation followed second-order kinetics. Moreover, we predicted the transformation pathways of TFA using density functional theory (DFT) and assessed the toxicity levels of TFA and its TPs to aquatic organisms using ECOSAR. Collectively, these findings hold significant implications for a better understanding of TFA fate in diversified soil, benefiting its risk assessment and rational utilization.

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Parabens are classified as emerging contaminants in global waters, and the ubiquitous emergence of their high-risk chlorinated products generated from chlorine-based wastewater disinfection has attracted increasing attention. However, rather limited information is available on their photofate after discharging into surface waters, and their degradation behavior after solar-based engineering water treatment is unclear. Herein, the reactivity of four chlorinated parabens with different photochemically produced reactive intermediates was measured. Quantitative contribution analysis in abating such compounds showed the dominance of direct photolysis in sunlit natural freshwaters. Introducing a technical solar/peroxymonosulfate (PMS) system could greatly improve the removal of chlorinated parabens. The economic analysis suggested that chlorinated parabens exhibited a minimum value of economic input as 93.41-158.04 kWh m-3 order-1 at 0.543-0.950 mM PMS. The high-resolution mass spectrometry analysis of the degradation products suggested that dechlorination, hydroxylation, and ester chain cleavage were the dominant transformation pathways during photolysis and solar/PMS treatment. Furthermore, the in silico prediction indicated severe aquatic toxicity of certain products but enhanced biodegradability. Overall, this investigation filled a knowledge gap on the reactivity of chlorinated parabens with diverse reactive transients and their quantitative contributions to the photolysis and solar/PMS treatment of emerging micropollutants in water.

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Wastewater treatment plants (WWTPs) serve as the main destination of many wastes containing per- and polyfluoroalkyl substances (PFAS). Here, we investigated the occurrence and transformation of PFAS and their transformation products (TPs) in wastewater treatment systems using high-resolution mass spectrometry-based target, suspect, and non-target screening approaches. The results revealed the presence of 896 PFAS and TPs in aqueous and sludge phases, of which 687 were assigned confidence levels 1-3 (46 PFAS and 641 TPs). Cyp450 metabolism and environmental microbial degradation were found to be the primary metabolic transformation pathways for PFAS within WWTPs. An estimated 52.3 %, 89.5 %, and 13.6 % of TPs were believed to exhibit persistence, bioaccumulation, and toxicity effects, respectively, with a substantial number of TPs posing potential health risks. Notably, the length of the fluorinated carbon chain in PFAS and TPs was likely associated with increased hazard, primarily due to the influence of biodegradability. Ultimately, two high riskcompounds were identified in the effluent, including one PFAS (Perfluorobutane sulfonic acid) and one enzymatically metabolized TP (23-(Perfluorobutyl)tricosanoic acid@BTM0024_cyp450). It is noteworthy that the toxicity of some TPs exceeded that of their parent compounds. The results from this study underscores the importance of PFAS TPs and associated environmental risks.

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Among the numerous organochlorines (OCs) applied in the French West Indies (FWI), chlordecone (hydrated form C10Cl10O2H2; CLD) still causes major environmental pollution nowadays. A recent report revealed the unexpected presence in FWI environment of transformation products (TPs) of CLD not routinely monitored due to a lack of commercial standards. Here, we present a method for surface waters and groundwaters to analyze CLD, its main TPs (hydroCLDs, chlordecol (CLDOH), 10-monohydroCLDOH and polychloroindenes) and other OCs. We developed an SPME-GC-SIM/MS method with a PDMS-DVB fiber. Since CLDOH-d commonly used as internal standard (IS) proved unsuitable, we synthesized several IS candidates, and finally identified 10-monohydro-5-methyl-chlordecol as a satisfactory IS for CLDOH and 10-monohydroCLDOH avoiding the use of 13C-labelled analogue. LODs for CLD and its TPs varied from 0.3 to 10 ng/L, equal to or below LODs of the two laboratories, BRGM (the French geological survey) and LDA26 (one of the French Departmental Analytical Laboratories), requested in FWI pollution monitoring that used liquid-liquid extractions and advanced facilities (LLE-GC-MS/MS and LLE-LC-MS/MS methods, respectively). Then, we extended the multi-residue method to 30 OCs (CLD and its TPs, mirex, ß-HCH, lindane, dieldrin, aldrin, HCB, hexachlorobutadiene, TCE, PCE) and applied it to 30 surface and ground waters from FWI. While CLD, 8- and 10-monohydroCLD, CLDOH, 10-monohydroCLDOH, dieldrin, and ß-HCH were detected and quantified, pentachloroindene, another CLD TP, was sporadically found in trace levels. A comparison with BRGM and LDA26 confirmed the interest of the SPME method. Results suggested an underestimation of CLDOH and an overestimation of high CLD concentrations with one of the currently used routine protocol. In light of these findings, previous temporal monitoring of environmental waters in FWI were re-examined and revealed some atypical values, which may indeed be due to analytical bias. These discrepancies call for intensified efforts to reliably quantify CLD and its TPs.

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Wastewater treatment plants (WWTPs) are an important source of pharmaceuticals in surface water, but information about their transformation products (TPs) is very limited. Here, we investigated occurrence and transformation of pharmaceuticals and TPs in WWTPs and receiving rivers by using suspect and non-target analysis as well as target analysis. Results showed identification of 113 pharmaceuticals and 399 TPs, including mammalian metabolites (n = 100), environmental microbial degradation products (n = 250), photodegradation products (n = 44) and hydrolysis products (n = 5). The predominant parent pharmaceuticals (n = 37) and transformation products (n = 68) were mainly derived from antimicrobials, accounting for 32.7 % and 17.0 %, respectively. The identified compounds were found in the influent (387-428) and effluent (227-400) of WWTPs, as well as upstream (290-451) and downstream (322-416) of receiving rivers, most predominantly from antimicrobials, followed by analgesic and antipyretic drugs. A total of 399 identified TPs were transformed by 110 pathways, of which the oxidation reaction was predominant (27.0 %), followed by photodegradation reaction (10.7 %). Of the 399 TPs, 49 (with lower PNECs) were predicted to be more toxic than their parents. Compounds with potential high risks (hazard quotient >1 and risk index (RI) > 0.1) were found in the WWTP influent (126), effluent (53) and river (61), and the majority were from the antimicrobial and antihypertensive classes. In particular, the potential risks (RI) of TPs from roxithromycin and irbesartan were found higher than those for their corresponding parents. The findings from this study highlight the need to monitor TPs from pharmaceuticals in the environment.

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Harmful cyanobacterial blooms will be more intense and frequent in the future, contaminating surface waters with cyanotoxins and posing a threat to communities heavily reliant on surface water usage for crop irrigation. Constructed wetlands (CWs) are proposed to ensure safe crop irrigation, but more research is needed before implementation. The present study operated 28 mesocosms in continuous mode mimicking horizontal sub-surface flow CWs. Mesocosms were fed with synthetic lake water and spiked periodically with two cyanotoxins, microcystin-LR (MC-LR) and cylindrospermopsin (CYN), at environmentally relevant cyanotoxins concentrations (10 µg L-1). The influence of various design factors, including plant species, porous media, and seasonality, was explored. The mesocosms achieved maximum MC-LR and CYN mass removal rates of 95 % and 98 %, respectively. CYN removal is reported for the first time in CWs mimicking horizontal sub-surface flow CWs. Planted mesocosms consistently outperformed unplanted mesocosms, with Phragmites australis exhibiting superior cyanotoxin mass removal compared to Juncus effusus. Considering evapotranspiration, J. effusus yielded the least cyanotoxin-concentrated effluent due to the lower water losses in comparison with P. australis. Using the P-kC* model, different scaling-up scenarios for future piloting were calculated and discussed. Additionally, bacterial community structure was analyzed through correlation matrices and differential taxa analyses, offering valuable insights into their removal of cyanotoxins. Nevertheless, attempts to validate microcystin-LR biotransformation via the known mlrA gene degradation pathway were unfruitful, indicating alternative enzymatic degradation pathways occurring in such complex CW systems. Further investigation into the precise molecular mechanisms of removal and the identification of transformation products is needed for the comprehensive understanding of cyanotoxin mitigation in CW. This study points towards the feasibility of horizontal sub-surface flow CWs to be employed to control cyanotoxins in irrigation or recreational waters.

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Ozonation is used worldwide for drinking water disinfection and increasingly also for micropollutant abatement from wastewater. Identification of transformation products formed during the ozonation of micropollutants is challenging due to several factors including (i) the reactions of both oxidants, ozone and hydroxyl radicals with the micropollutants, as well as with intermediate transformation products, (ii) effects of the water matrix on the ozone and hydroxyl radical chemistry and (iii) the generation of oxidation by-products. In this study, a simple approach to achieve realistic ozonation conditions in the absence of dissolved organic matter has been developed. It is based on composing synthetic water matrices with low-molecular-weight scavenger compounds (phenol, methanol, acetate, and carbonate) that mimic the chemical interactions of ozone and hydroxyl radicals with real water matrices. Synthetic waters composed of only four low-molecular-weight compounds successfully replicated two lake waters and two secondary wastewater effluents, matching instantaneous ozone demand, ozone and hydroxyl radical exposures in the initial phase, as well as the ozone evolution in the second phase of the ozonation process. The synthetic water matrices also reproduced the effects of temperature and pH changes observed in real waters. The abatement of two micropollutants, bezafibrate and atrazine, and the formation of the corresponding transformation products during ozonation were in agreement for synthetic and real waters. Furthermore, the kinetics and extent of bromate formation during ozonation in synthetic water were comparable to real lake water and wastewater. This supports the robustness of the proposed approach because bromate formation is very sensitive to the interplay of ozone and hydroxyl radicals. Furthermore, with the novel reaction system, a significant effect of hydroxyl radicals scavenging by carbonate on bromate formation was demonstrated. Overall, the herein-developed approach based on synthetic water matrices allows to perform realistic ozonation studies including both oxidants, ozone and hydroxyl radicals, without the constraints of using dissolved organic matter.

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Tetracyclines (TCs) are the most common antibiotics in agricultural soil, due to their widespread usage and strong persistence. Biotic and abiotic degradation of TCs may generate toxic transformation products (TPs), further threatening soil ecological safety. Despite the increasing attention on the environmental behavior of TCs, a systematic review on the dissipation of TCs, evolution of TPs, and structure-toxicity relationship of TCs in agricultural soil remains lacking. This review aimed to provide a comprehensive overview of the environmental fate of TCs in agricultural soil. We first introduced the development history and structural features of different generations of TCs. Then, we comparatively evaluated the dissipation kinetics, transportation pathways, and ecological impacts of three representative TCs, namely tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC), in agricultural soil. The results showed that the dissipation kinetics of TCs generally followed the first-order kinetic model, with the median dissipation half-lives ranging from 20.0 to 38.8 days. Among the three TCs, OTC displayed the lowest dissipation rates due to its structural stability. The typical degradation pathways of TCs in soil included epimerization/isomerization, demethylation, and dehydration. Isomerization and dehydration reactions may lead to the formation of more toxic TPs, while demethylation was accompanied by the alteration of the minimal pharmacophore of TCs thus potentially reducing the toxicity. Toxicological experiments are urgently needed in future to comprehensively evaluate the ecological risks of TCs in agricultural soil.

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Sulfamethoxazole (SMX) passes through conventional wastewater treatment plants (WWTPs) mainly unaltered. Under anoxic conditions sulfate-reducing bacteria can transform SMX but the fate of the transformation products (TPs) and their prevalence in WWTPs remain unknown. Here, we report the anaerobic formation and aerobic degradation of SMX TPs. SMX biotransformation was observed in nitrate- and sulfate-reducing enrichment cultures. We identified 10 SMX TPs predominantly showing alterations in the heterocyclic and N4-arylamine moieties. Abiotic oxic incubation of sulfate-reducing culture filtrates led to further degradation of the major anaerobic SMX TPs. Upon reinoculation under oxic conditions, all anaerobically formed TPs, including the secondary TPs, were degraded. In samples collected at different stages of a full-scale municipal WWTP, anaerobically formed SMX TPs were detected at high concentrations in the primary clarifier and digested sludge units, where anoxic conditions were prevalent. Contrarily, their concentrations were lower in oxic zones like the biological treatment and final effluent. Our results suggest that anaerobically formed TPs were eliminated in the aerobic treatment stages, consistent with our observations in batch biotransformation experiments. More generally, our findings highlight the significance of varying redox states determining the fate of SMX and its TPs in engineered environments.

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Unplanned water reuse for crop irrigation may pose a global health risk due to the entry of contaminants into the food chain, undesirable effects on crop quality, and impact on soil health. In this study, we evaluate the impact derived from the co-occurrence of pharmaceuticals (Phs), trace metals (TMs), and one metalloid within the water-soil-plant continuum through bioassay experiments with Lactuca sativa L. Results indicate that the co-occurrence of Phs and TMs has synergistic or antagonistic effects, depending on target contaminants and environmental compartments. Complex formations between drugs and TMs may be responsible for enhanced sorption onto the soil of several Phs and TMs. Concerning plant uptake, the co-occurrence of Phs and TMs exerts antagonistic and synergistic effects on carbamazepine and diazepam, respectively. With the exception of Cd, drugs exert an antagonistic effect on TMs, negatively affecting their uptake and translocation. Drug contents in lettuce edible parts do not pose any threat to human health, but Cd levels exceed the maximum limits set for leafy vegetable foodstuffs. Under Ph-TM conditions, lettuce biomass decreases, and a nutrient imbalance is observed. Soil enzyme activity is stimulated under Ph-TM conditions (ß-galactosidase) and Ph and Ph-TM conditions (urease and arylsulfatase), or it is not affected (phosphatase).

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Flupyradifurone (FPF) is considered the latest generation of neonicotinoid insecticides. Here, we investigated the toxicity and ecological risk of FPF and its aerobic transformation products (TPs) to aquatic species using the method of prediction. We found that FPF exhibited moderate or high toxicity to some aquatic species. The 5% hazardous concentration of FPF was 3.84 µg/L for aquatic organisms. We obtained 91 aerobic TPs for FPF, and almost half of FPF TPs exhibited toxicity to fish or Daphnia. Eleven of the TPs of FPF exhibited a high or moderate risk to aquatic ecosystems. All FPF TPs with high and moderate risks contained a 6-chloropyridine ring structure, indicating that the derivant of a pyridine ring exhibits potential risks to aquatic ecosystems. Our results provide insight into the potential risk of FPF to aquatic ecosystems and could be used to help set criteria to control pollution caused by FPF.

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Photocatalysis is a prominent alternative wastewater treatment technique that has the potential to completely degrade pesticides as well as other persistent organic pollutants, leading to detoxification of wastewater and thus paving the way for its efficient reuse. In addition to the more conventional photocatalysts (e.g., TiO2, ZnO, etc.) that utilize only UV light for activation, the interest of the scientific community has recently focused on the development and application of visible light-activated photocatalysts like g-C3N4. However, some disadvantages of g-C3N4, such as the high recombination rate of photogenerated charges, limit its utility. In this light, the present study focuses on the synthesis of WO3 fibers/g-C3N4 Z-scheme heterojunctions to improve the efficiency of g-C3N4 towards the photocatalytic removal of the widely used insecticide clothianidin. The effect of two different g-C3N4 precursors (urea and thiourea) and of WO3 fiber content on the properties of the synthesized composite materials was also investigated. All aforementioned materials were characterized by a number of techniques (XRD, SEM-EDS, ATR-FTIR, Raman spectroscopy, DRS, etc.). According to the results, mixing 6.5% W/W WO3 fibers with either urea or thiourea derived g-C3N4 significantly increased the photocatalytic activity of the resulting composites compared to the precursor materials. In order to further elucidate the effect of the most efficient composite photocatalyst in the degradation of clothianidin, the generated transformation products were tentatively identified through UHPLC tandem high-resolution mass spectroscopy. Finally, the detoxification effect of the most efficient process was also assessed by combining the results of an in-vitro methodology and the predictions of two in-silico tools.

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This study aims the characterization of several tianeptine transformation products in ultrapure water by simulated sunlight irradiation. Tianeptine was completely degraded after 106 h of exposition following pseudo-first-order kinetics (half-life time = 12.0 ± 2.4 h). Furthermore, an ultra-high-performance liquid chromatography coupled with a high-resolution quadrupole time-of-flight-mass spectrometry method was developed and fully validated taking into account different method performance parameters for the quantification of tianeptine in river water up to a concentration of 400 pg L-1. Following a non-targeted approach based on mass data-independent acquisition, eight different transformation products not previously reported in the literature were identified and accordingly elucidated, proposing a photodegradation mechanism based on the accurate tandem mass spectrometry information acquired. Irradiation experiments were replicated for a tianeptine solution prepared in a blank river water sample, resulting in the formation of the same transformation products and similar degradation kinetics. In addition, a toxicity assessment of the photoproducts was performed by in silico method, being generally all TPs of comparable toxicity to the precursor except for TP1, and showing a similar persistence in the environment except for TP2 and TP6, while TP4 was the only TP predicted as mutagenic. The developed method was applied for the analysis of four river water samples.

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N-(1,3-Dimethyl butyl)-N'-phenyl-phenylenediamine-quinone (6PPD-Q) is a derivative of the widely used rubber tire antioxidant 6PPD, which was first found to be acutely toxic to coho salmon. Subsequent studies showed that 6PPD-Q had species-specific acute toxicity in fishes and potential hepatotoxicity in mice. In addition, 6PPD-Q has been reported in human urine, demonstrating the potential widespread exposure of humans to this chemical. However, whether 6PPD-Q poses a higher risk to humans than its parent compound, 6PPD, and could cause adverse effects in humans is still unclear. In this study, we utilized two human liver cell models (the human proto-hepatocyte model L02 and the human hepatocellular carcinoma cell line HepG2) to investigate the potentially differential effects of these two chemicals. Cell viability curve analysis showed that 6PPD-Q had lower IC50 values than 6PPD for both liver cell lines, suggesting higher toxicity of 6PPD-Q to human liver cells than 6PPD. In addition, L02 cells are more sensitive to 6PPD-Q exposure, which might be derived from its weaker metabolic transformation of 6PPD-Q, since significantly lower levels of phase I and phase II metabolites were detected in 6PPD-Q-exposed L02 cell culture medium. Furthermore, pathway analysis showed that 6PPD-Q exposure induced changes in phenylalanine, tyrosine, and tryptophan biosynthesis and tyrosine metabolism pathways in L02 cells, which might be the mechanism underlying its liver cell toxicity. Gene expression analysis revealed that exposure to 6PPD-Q induced excessive ROS production in L02 cells. Our results further supported the higher risk of 6PPD-Q than 6PPD and provided insights for understanding the effects of 6PPD-Q on human health.

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Among rising environmental concerns, emerging contaminants constitute a variety of different chemicals and biological agents. The composition, residence time in environmental media, chemical interactions, and toxicity of emerging contaminants are not fully known, and hence, their regulation becomes problematic. Some of the important groups of emerging contaminants are pesticides and pesticide transformation products (PTPs), which present a considerable obstacle to maintaining and preserving ecosystem health. This review article aims to thoroughly comprehend the occurrence, fate, and ecotoxicological importance of pesticide transformation products (PTPs). The paper provides an overview of pesticides and PTPs as contaminants of emerging concern and discusses the modes of degradation of pesticides, their properties and associated risks. The degradation of pesticides, however, does not lead to complete destruction but can instead lead to the generation of PTPs. The review discusses the properties and toxicity of PTPs and presents the methods available for their detection. Moreover, the present study examines the existing regulatory framework and suggests the need for the development of new technologies for easy, routine detection of PTPs to regulate them effectively in the environment.

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Mariculture effluent polishing with microalgal biofilm could realize effective nutrients removal and resolve the microalgae-water separation issue via biofilm scraping or in-situ aquatic animal grazing. Ubiquitous existence of antibiotics in mariculture effluents may affect the remediation performances and arouse ecological risks. The influence of combined antibiotics exposure at environment-relevant concentrations towards attached microalgae suitable for mariculture effluent polishing is currently lack of research. Results from suspended cultures could offer limited guidance since biofilms are richer in extracellular polymeric substances that may protect the cells from antibiotics and alter their transformation pathways. This study, therefore, explored the effects of combined antibiotics exposure at environmental concentrations towards seawater Chlorella sp. biofilm in terms of microalgal growth characteristics, nutrients removal, anti-oxidative responses, and antibiotics removal and transformations. Sulfamethoxazole (SMX), tetracycline (TL), and clarithromycin (CLA) in single, binary, and triple combinations were investigated. SMX + TL displayed toxicity synergism while TL + CLA revealed toxicity antagonism. Phosphorus removal was comparable under all conditions, while nitrogen removal was significantly higher under SMX and TL + CLA exposure. Anti-oxidative responses suggested microalgal acclimation towards SMX, while toxicity antagonism between TL and CLA generated least cellular oxidative damage. Parent antibiotics removal was in the order of TL (74.5-85.2 %) > CLA (60.8-69.5 %) > SMX (13.5-44.1 %), with higher removal efficiencies observed under combined than single antibiotic exposure. Considering the impact of residual parent antibiotics, CLA involved cultures were identified of high ecological risks, while medium risks were indicated in other cultures. Transformation products (TPs) of SMX and CLA displayed negligible aquatic toxicity, the parent antibiotics themselves deserve advanced removal. Four out of eight TPs of TL could generate chronic toxicity, and the elimination of these TPs should be prioritized for TL involved cultures. This study expands the knowledge of combined antibiotics exposure upon microalgal biofilm based mariculture effluent polishing.

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