Azole and strobilurin fungicides in source, treated, and tap water from Wuhan, central China: Assessment of human exposure potential

Pyraclostrobin-induced toxic effects in the gills of common carp (Cyprinus carpio L.): Mechanisms unveiled through biochemical, molecular, and metabolomic analyses

Pyraclostrobin (PYR) is widely used in agriculture to control fungal infestations. However, the toxic effects of PYR on aquatic organisms remain poorly understood. In this study, common carp were exposed to 0.5, and 5.0 μg/L PYR for 30 days to evaluate the chronic effects on gill health via histopathological, biochemical, molecular, and metabolomic analyses. The findings revealed that exposure to PYR resulted in significant histopathological alterations, suppression of mitochondrial complex III activity, and excessive production of reactive oxygen species (ROS), including O2•- and H2O2. Additionally, PYR exposure altered the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) while increasing the malondialdehyde (MDA) content in the gills of common carp. The protein expression levels of lysozyme (LZM), tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and transforming growth factor beta (TGF-β) were significantly elevated following exposure to PYR, whereas the levels of complement 3 (C3) and immunoglobulin M (IgM) were decreased. Furthermore, the amount of IL-6 decreased on day 15 before increasing on day 30. Further analysis revealed a notable increase in acid phosphatase (ACP) activity and a decrease in alkaline phosphatase (AKP) activity after 30 days of PYR exposure. Moreover, PYR exposure significantly altered the mRNA expression levels of immune-related genes (lzm, c3, and igm) and apoptosis-related genes (p53, bcl-2, bax, caspase-3, and caspase-9). Several inflammatory markers, such as NF-κB p65 protein and the mRNA levels of tlr2, tlr4, myd88, tnf-α, il-1β, il-6, and tgf-β, were also markedly changed. Metabolomic studies demonstrated that PYR influences pathways related to amino acid, nucleotide, arachidonic acid, and linoleic acid metabolism. These results indicate that PYR adversely affects gill health by inducing oxidative stress, disrupting immune and inflammatory responses, affecting apoptosis-related pathways, and altering metabolic homeostasis. This study provides new insights into the toxic mechanisms of PYR and contributes to the assessment of the ecological risks associated with its presence in aquatic ecosystems.

Long-term study of azoles in surface water and treated wastewater

Azole antifungals are commonly used as pharmaceuticals, cosmetics as well as agricultural fungicides. Such an extensive range of applications of azole compounds leads to their widespread occurrence in wastewater and surface waters. In this study, the quantitative determination of antifungal pharmaceuticals (fluconazole, climbazole, clotrimazole) and fungicides (tebuconazole, epoxiconazole, flutriafol, tiabendazole, and imazalil) was seasonally performed in surface water samples from rivers, lakes and field drainage ditches as well as wastewater treatment plants (WWTP) effluents in western Poland. Solid phase extraction (SPE) combined with high-performance liquid chromatography-tandem mass spectrometry was used to detect azole compounds in waters, obtaining recoveries up to 100.2% with relative standard deviations below 9%. Azole monitoring was conducted for 3 years in treated wastewater and surface water. Fluconazole was the compound determined at the highest concentrations in all analyzed WWTP effluents, reaching 739 ng L-1. The concentration of 100 ng L-1 was also exceeded by climbazole, clotrimazole, tiabendazole, and imazalil, which proves that these compounds are not completely removed by the degradation processes used in WWTPs and are released into the environment. In surface waters analysis, definitely the highest concentration was obtained for tebuconazole - 1383 ng L-1 in Warta River and 1783 ng L-1 in a field drainage ditch, which is caused by its extensive application as an agricultural fungicide. The majority of the analyzed azole antifungals are present in WWTP effluents and surface water, highlighting the need for future monitoring and investigation of their degradation methods. However, the present results show that determined concentrations are safe for aquatic organisms.

Exposure to organophosphates, pyrethroids, neonicotinoids, and pentachlorophenol: Spatial variations in urinary biomarkers and associations with oxidative stress based on a repeated-measure study

It is important to identify priority regions regarding contaminant exposure, especially for environmental epidemiological studies. Whereas very few studies explored spatial variations in concentrations of multiple insecticide metabolites in the general population, as well as their relationship with oxidative stress biomarkers (OSBs). We determined related target analytes in urine samples (n = 850) from 425 healthy adults in six cities of China during both autumn and winter. Eight organophosphorus metabolites (mOPPs), three pyrethroid metabolites (mPYRs), nine neonicotinoid insecticide metabolites (mNNIs), and pentachlorophenol (PCP) were detected in the urine samples. Additionally, linear mixed-effects model and weighted quantile sum model were used to assess the individual and combined effects of the insecticide exposure on selected OSBs. Altogether, 17 out of the 21 analytes were widely detected (73.1-100%). The median specific gravity (SG)-adjusted concentrations for the mOPPs, mPYRs, mNNIs, and PCP were 1.17-4.85, 0.45-0.79, 0.09-1.07, and 0.38 ng/mL, respectively. The mOPPs in Lanzhou (northwest China), mPYRs and mNNIs in Dalian (northeast China), and PCP in Chengdu (southwest China) had the highest concentrations among the six cities. The concentrations of the mNNIs and PCP in urban areas were significantly higher than those in rural areas, while the concentrations of some mOPPs and mPYRs were higher in rural areas. The concentrations of most analytes were higher in autumn than in winter. Hazard quotient of >1 for chlorpyrifos was observed in 9.2% of the study participants, suggested a potential health risk, while the estimated daily intake values of the other analytes were lower than their chronic reference doses. Many of the insecticide exposure biomarkers were significantly associated with increased OSBs; among them, each interquartile range-fold increase in the insecticide exposure biomarkers was associated with 5.4-19.0%, 4.6-19.4%, and 12.4-83.3% increase in 8-hydroxy-2'-deoxyguanosine, 8-hydroxy guanosine, and 4-hydroxy-2-nonenal-mercapturic acid, respectively. P-Nitrophenol was the main contributor in the association with the increased OSBs. This study found significant variations in insecticide exposure levels among different regions and seasons. The exposure level of chlorpyrifos suggested a potential health risk, and the insecticide mixture exposure was significantly associated with increased OSBs. Further risk assessments are warranted and control measures in the insecticide use are needed to mitigate the potential health risks.

Occurrence, Bioaccumulation, and Human Exposure Risk of the Antiandrogenic Fluorescent Dye 7-(Dimethylamino)-4-methylcoumarin and 7-(Diethylamino)-4-methylcoumarin in the Dongjiang River Basin, South China

Recently, 7-diethylamino-4-methylcoumarin (DEAMC) has been identified as a potent antiandrogenic compound in the surface water; however, little is known about the antiandrogenic potentials of other synthetic coumarins and their occurrence in the aquatic ecosystem. In this study, for the first time, we observed that 7-dimethylamino-4-methylcoumarin (DAMC) elicited androgen receptor (AR) antagonistic activity with a 50% inhibitory concentration (IC50) of 1.46 µM, which is 14.3 times more potent than that observed for DEAMC (IC50 = 20.92 µM). We further collected abiotic (water and sediment) and biotic (plant, plankton, and fish) samples (n = 208) from a subtropical freshwater ecosystem, the Dongjiang River basin, in southern China, and determined the concentrations of the two coumarins in these samples. Overall, DAMC was the predominant compound found in the sediment, plant, algae, zooplankton, and fish muscle samples, with median concentrations at 0.189, 0.421, 0.832, 0.798, and 0.335 ng/g dry wt. (DW), respectively, although it was not detected in any surface water sample. For DEAMC, the median concentrations observed in the surface water, sediment, plant, algae, zooplankton, and fish muscle samples were 0.105 ng/L, 0.012, 0.051, 0.009, 0.008, and 0.181 ng/g DW, respectively. The bioaccumulation factor (BAF) values of DAMC and DEAMC in the algae, zooplankton, and fish muscle exceeded 5000 L/kg, suggesting that the two coumarins may have significant bioaccumulation potentials in aquatic biota. Additionally, the mean daily intake (EDI) of coumarins through fish consumption was estimated as 0.19 ng/kg BW/day for male toddlers. This is the first field study to illustrate the antiandrogenic potential of DAMC and document the widespread occurrence of the two synthetic coumarins in aquatic ecosystems.

A paper-based lateral flow immunochromatographic sensor for the detection of tricyclazole in rice

Tricyclazole is commonly used to prevent rice blast to meet the carbohydrate intake needs of half of the global population, and a large number of toxicological reports indicate that monitoring of tricyclazole is necessary. Here, we analyzed the structure of tricyclazole and designed different hapten derivatization strategies to prepare a high-performance monoclonal antibody (half inhibition concentration of 1.61 ng/mL), and then a lateral flow immunochromatographic sensor based on gold nanoparticles for the detection of tricyclazole in rice, with a limit of detection of 6.74 μg/kg and 13.58 μg/kg in polished and brown rice, respectively. The recoveries in rice were in the range of 84.6-107.4%, no complex pretreatment was required for comparison with LC-MS/MS, and the comparative analysis demonstrated that our method had good accuracy and precision. Therefore, the developed lateral flow immunochromatographic analysis was a reliable and rapid means for the on-site analysis of tricyclazole in rice.

Chitosan-based emulsive liquid-liquid microextraction for the determination of strobilurin fungicides in water samples

Strobilurin fungicides are widely used pesticides globally; however, their residues pose a risk to environmental safety and human health. This study aimed to develop a rapid and green method for detecting strobilurin fungicide residues. Chitosan and magnetic deep eutectic solvent-based emulsive liquid-liquid microextraction method combined with high-performance liquid chromatography was developed to determine strobilurin fungicides in water samples. A high-concentration oil-in-water emulsion containing chitosan solution and extractant was formulated, followed by the addition of samples to form a low-concentration oil-in-water emulsion to complete the rapid pretreatment, therefore solving the limitation of emulsive liquid-liquid microextraction in the inapplicability of extractants. Traditional microextraction required toxic solvents and complex equipment to facilitate the dispersion of extractants, whereas this study used only chitosan solution to aid in emulsifying extractants. The new green magnetic deep eutectic solvent synthesized by tetraoctylammonium bromide, ferric chloride, and oleic acid was used instead of toxic extractants. An external magnetic field assisted the extractant phase collection, which shortened the separation time. Under optimal conditions, the recovery of this method was 83.3 %-107.4 %, the limit of detection was 0.0010-0.0021 mg L-1, and the coefficient of determination was >0.994. This rapid, green, simple, and efficient chitosan-based microextraction method could detect strobilurin fungicide residues in water samples because of its enhanced compatibility with hydrophobicity extractants.

Identification of emerging PFAS in industrial sludge from North China: Release risk assessment by the TOP assay

Per- and polyfluoroalkyl substances (PFAS) have been widely used across various industries, leading to their prevalent occurrence in sludges generated by wastewater treatment plants (WWTPs). Consequently, industrial sludges serve as typical reservoirs for PFAS. This study examined 46 target PFAS in sludge samples intended for brick production from nine WWTPs in North China, identifying emerging PFAS and categorizing their behaviors through high-resolution mass spectrometry (HRMS) screening and total oxidizable precursor (TOP) assay. Forty-one PFAS were detected, with trifluoroacetic acid (TFA), perfluorooctane sulfonic acid, and hexafluoropropylene oxide dimer acid being the most prevalent. Twenty-nine emerging PFAS were identified, and their behaviors were categorized using TOP assay. Notably, four CF3-containing PFAS were identified, all confirmed as precursors of TFA, with a molar yield of 16.4 %-25.6 % in Milli-Q water during TOP assay validation. These findings indicate that the transformation of these precursors during sludge recycling may substantially contribute to TFA release, underscoring potential risks associated with secondary PFAS release during sludge resource utilization.

A high-affinity fluorescent probe for human uridine-disphosphate glucuronosyltransferase 1A9 function monitoring under environmental pollutant exposure

Uridine-disphosphate glucuronosyltransferase 1A9 (UGT1A9), an important detoxification and inactivation enzyme for toxicants, regulates the exposure level of environmental pollutants in the human body and induces various toxicological consequences. However, an effective tool for high-throughput monitoring of UGT1A9 function under exposure to environmental pollutants is still lacking. In this study, 1,3-dichloro-7-hydroxy-9,9-dimethylacridin-2(9H)-one (DDAO) was found to exhibit excellent specificity and high affinity towards human UGT1A9. Remarkable changes in absorption and fluorescence signals after reacting with UGT1A9 were observed, due to the intramolecular charge transfer (ICT) mechanism. Importantly, DDAO was successfully applied to monitor the biological functions of UGT1A9 in response to environmental pollutant exposure not only in microsome samples, but also in living cells by using a high-throughput screening method. Meanwhile, the identified pollutants that disturb UGT1A9 functions were found to significantly influence the exposure level and retention time of bisphenol S/bisphenol A in living cells. Furthermore, the molecular mechanism underlying the inhibition of UGT1A9 by these pollutant-derived disruptors was elucidated by molecular docking and molecular dynamics simulations. Collectively, a fluorescent probe to characterize the responses of UGT1A9 towards environmental pollutants was developed, which was beneficial for elucidating the health hazards of environmental pollutants from a new perspective.

Toxicological impact of strobilurin fungicides on human and environmental health: a literature review

Fungicides are specifically used for controlling fungal infections. Strobilurins, a class of fungicides originating from the mushroom Strobilurus tenacellus, act on the fungal mitochondrial respiratory chain, interrupting the ATP cycle and causing oxidative stress. Although strobilurins are little soluble in water, they have been detected in water samples (such as rainwater and drinking water), indoor dust, and sediments, and they can bioaccumulate in aquatic organisms. Strobilurins are usually absorbed orally and are mainly eliminated via the bile/fecal route and urine, but information about their metabolites is lacking. Strobilurins have low mammalian toxicity; however, they exert severe toxic effects on aquatic organisms. Mitochondrial dysfunction and oxidative stress are the main mechanisms related to the genotoxic damage elicited by toxic compounds, such as strobilurins. These mechanisms alter genes and cause other dysfunctions, including hormonal, cardiac, neurological, and immunological impairment. Despite limitations, we have been able to compile literature information about strobilurins. Many studies have dealt with their toxic effects, but further investigations are needed to clarify their cellular and underlying mechanisms, which will help to find ways to minimize the harmful effects of these compounds.

Impacts of pyraclostrobin on intestinal health and the intestinal microbiota in common carp (Cyprinus carpio L.)

Pyraclostrobin (PYR) is a strobilurin fungicide that is commonly used in agriculture, and its use in agriculture may lead to an increase in its residue in the aquatic environment and may have a deleterious influence on the intestinal health of aquatic creatures. Here, common carp were chronically exposed to PYR (0, 0.5, or 5.0 μg/L) for 30 d to determine its effect on the physical and immunological barrier and intestinal microbiota in the intestine. PYR exposure caused significant histological changes; altered the mRNA expression levels of occludin, claudin-2, and zonula occludens-1 (ZO-1); induced oxidative stress in the common carp intestine; and increased the serum D-lactate and diamine oxidase (DAO) levels. Moreover, PYR significantly increased the protein expression levels of tumour necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and IL-6 while decreasing the level of transforming growth factor beta (TGF-β). Further studies revealed that PYR significantly reduced lysozyme (LZM) and acid phosphatase (ACP) activities as well as complement 3 (C3) and immunoglobulin M (IgM) levels. Furthermore, PYR decreased gut microbial diversity while increasing the abundance of pathogenic bacteria such as Aeromonas and Shewanella, causing an intestinal microbial disturbances in common carp. These results imply that PYR has a negative impact on fish intestinal health and may pose serious health risks to fish by disrupting the intestinal microbiota, physical barrier, and immunological barrier in common carp.

Evidence of strobilurin fungicides and their metabolites in Dongjiang River ecosystem, southern China: Bioaccumulation and ecological risks

Despite the widespread application of strobilurin fungicides (SFs) in agriculture, little is known about their distribution and bioaccumulation in aquatic ecosystems. In this study, the concentrations of 12 SFs and two of their metabolites were determined in abiotic (water and sediment; n = 83) and biotic (plant, algae, zooplankton, and fish; n = 123) samples collected from a subtropical freshwater ecosystem, namely, Dongjiang River wetland, in southern China. Among the 12 SFs measured, azoxystrobin (AZ) was the major fungicide found in surface water (median: 2.20 ng/L) and sediment (0.064 ng/g dry wt.). Azoxystrobin acid (AZ-acid), a metabolite of AZ, was the major analyte in the plant samples and had a median concentration at 0.36 ng/g dry wt. In algae and zooplankton, (Z)-metominostrobin was the predominant fungicide and had median concentrations of 3.52 and 5.55 ng/g dry wt., respectively. In fish muscle, dimoxystrobin (DIMO) was the major SF and had a median concentration of 0.47 ng/g dry wt. The bioconcentration factor (BCF) values of AZ-acid, trifloxystrobin (TFS), and pyraclostrobin (PYR) in algae and zooplankton and AZ-acid, PYR, TFS, TFS-acid, picoxystrobin, and DIMO in fish muscle exceeded 1000 L/kg (algae, zooplankton, and fish concentrations were expressed on a dry weight basis), suggesting that these fungicides can accumulate in biota. A positive association between log BCFs of SFs in fish and logKow of SFs and a negative correlation between log BCFs and the log solubility index were observed. Additionally, the risk quotient (RQ) was calculated to evaluate the potential ecotoxicological risk of SFs to different aquatic organisms (algae, zooplankton, and fish). The PYR and DIMO concentrations at 19 sampling sites had RQ values >0.1, indicating moderate ecotoxicological risks to aquatic organisms. This study is the first to document the widespread occurrence of SFs and their metabolites in aquatic ecosystems and to elucidate the bioaccumulation potential of SFs in aquatic organisms.

Uptake, Translocation, and Subcellular Distribution of Strobilurin Fungicides in Cucumber (Cucumis sativa L.)

The absorption, transport, and subcellular distribution of strobilurin fungicides (azoxystrobin, pyraclostrobin, and trifloxystrobin) have been studied in cucumbers. Under hydroponic laboratory conditions, pyraclostrobin and trifloxystrobin mainly accumulated in cucumber roots whereas azoxystrobin accumulated in cucumber leaves. In the subcellular distribution experiment, azoxystrobin mainly accumulated as a soluble component. Pyraclostrobin and trifloxystrobin accumulated more in the organelles and cell walls. Azoxystrobin and pyraclostrobin enter the root primarily through the apoplast pathway, whereas trifloxystrobin enters the root through the symplastic pathway. Azoxystrobin can be transported in cucumber through anion and cation channels, whereas pyraclostrobin and trifloxystrobin can be transported only through anion channels. This study has great significance in evaluating environmental risks and food safety.

Hotspot mutations and genomic expansion of ERG11 are major mechanisms of azole resistance in environmental and human commensal isolates of Candida tropicalis

OBJECTIVES

Infections caused by azole-resistant Candida tropicalis strains are increasing in clinical settings. The reason for this epidemical change and the mechanisms of C. tropicalis azole resistance are not fully understood.

METHODS

In this study, we performed biological and genomic analyses of 239 C. tropicalis strains, including 115 environmental and 124 human commensal isolates.

RESULTS

Most (99.2%) of the isolates had a baseline diploid genome. The strains from both environmental and human niches exhibit similar abilities to survive under stressful conditions and produce secreted aspartic proteases. However, the human commensal isolates exhibited a stronger ability to filament than the environmental strains. We found that 19 environmental isolates (16.5%) and 24 human commensal isolates (19.4%) were resistant to fluconazole. Of the fluconazole-resistant strains, 37 isolates (86.0%) also exhibited cross-resistance to voriconazole. Whole-genome sequencing and phylogenetic analyses revealed that both environmental and commensal isolates were widely distributed in a number of genetic clusters, but the two populations exhibited a close genetic association. The majority of fluconazole-resistant isolates were clustered within a single clade (X).

CONCLUSIONS

The combination of hotspot mutations (Y132F and S154F) and genomic expansion of ERG11, which encodes the azole target lanosterol 14-α-demethylase and represents a major target of azole drugs, was a major mechanism for the development of azole resistance. The isolates carrying both hotspot mutations and genomic expansion of ERG11 exhibited cross-resistance to fluconazole and voriconazole. Moreover, the azole-resistant isolates from both the environmental and human commensal niches showed similar genotypes.

Degradation of azoxystrobin, methoxyfenozide, and propyzamide by ultrasound treatment

Ultrasound as a green and efficient process gains special attention in wastewater treatment. The ultrasound-assisted degradation of azoxystrobin, methoxyfenozide, and propyzamide as widely used pesticides for vine treatment was investigated. A wide range of ultrasonic power (40 to 140 W) and a single frequency (20 kHz) were applied. Degradation experiments were carried out according to the parameters set by a central composite design (CCD) under response surface methodology (RSM) via JMP software. The treatment efficiency was quantified using degradation rates and hydrogen peroxide (H2O2) measurements. Results indicated that the pesticide's degradation was negligible at 40 W but by increasing the power setting from 80 to 140 W, the degradation rate constants of azoxystrobin, methoxyfenozide, and propyzamide increased from 3.6 × 10-2 min-1 to 0.2 min-1, from 6.1 × 10-2 min-1 to 0.3 min-1, and from 3.1 × 10-2 min-1 to 0.1 min-1, respectively. The hydrogen peroxide (H2O2) measurements confirmed this trend. Besides, electric energy per order of pollutant removal (EE/O) was also evaluated for the same treatment duration and results revealed that treatment conditions of 20 kHz and 140 W were the less energy-guzzling. Finally, profiles obtained with RSM illustrated linear degradation kinetics for azoxystrobin and propyzamide. Indeed, treatment efficiency increased when increasing both studied parameters. However, both linear and quadratic degradation kinetics occurred for methoxyfenozide degradation indicating a parameter threshold beyond which the trend is reversed. Overall, this study confirms the effectiveness of ultrasound for the degradation of pesticides in aqueous medium.

Occurrence, spatial variation, seasonal difference, and risk assessment of neonicotinoid insecticides, selected agriculture fungicides, and their transformation products in the Yangtze River, China: From the upper to lower reaches

Neonicotinoid insecticides (NNIs) and agricultural fungicides (including strobilurin, azole, and morpholine fungicides) are widely used, while data on their contamination in the Yangtze River of China and the risks posed by them are limited. The occurrence and distribution of ten NNIs, twenty-one transformation products (TPs) of them, seventeen agricultural fungicides, and six TPs of them were investigated in the main stream of the Yangtze River. Surface water samples (n = 144) were obtained from 72 sampling points in dry season and wet season. Among the NNIs, the detection frequencies (DFs) of acetamiprid (ACE), clothianidin, dinotefuran, flonicamid, imidacloprid (IMI), thiacloprid (THCP), and thiamethoxam (THM) were higher than 85%, with the median concentrations ranged from 0.06 ng/L (THCP) to 3.63 ng/L (IMI). The DFs of the TPs descyano-acetamiprid, desmethyl-acetamiprid (DM-ACE), N-[(6-Chloropyridin-3-yl) methyl] methylamine, desnitro-clothianidin, desnitro-imidacloprid, desnitro-thiamethoxam, imidacloprid-urea, and thiamethoxam-urea (THM-urea) were higher than 80%, with the median concentrations ranged from 0.25 ng/L for DM-ACE to 2.41 ng/L for THM-urea. Some agricultural parent fungicides, including azoxystrobin (AZS), carbendazim (CBDZ), difenoconazole, dimethomorph, propiconazole, pyraclostrobin, and tebuconazole (TBCZ), were detected in all the samples; others were also detected in more than 80% of the samples except for fluoxastrobin (12.5%). The median concentrations of the frequently detected fungicides ranged from 0.02 ng/L (trifloxystrobin) to 26.8 ng/L (CBDZ). The DFs of the fungicide TPs azoxystrobin acid (AZS acid), difenoconazole-alcohol, tebuconazole-tert-butylhydroxy (TBCZ-OH), and 5-hydroxymethyl-tricyclazole were higher than 75%, with the median concentrations ranged from 0.09 ng/L (TBCZ-OH) to 1.80 ng/L (AZS acid). The summed concentrations of the NNIs and their TPs at the sampling points varied between 0.23 and 418 ng/L, and the summed concentrations of the selected fungicides and their TPs varied from 0.29 to 1160 ng/L. The spatial distribution of most target analytes revealed an increasing trend in their concentrations from the upstream to downstream Yangtze River (250 times increase in their cumulative concentration). Most target pesticides in this study had significantly higher concentrations during wet season than those during dry season. Furthermore, ecological risk assessment suggested that ACE, IMI, THM, CBDZ, TBCZ, and thifluzamide in some samples (n = 1, 11, 1, 1, 1, and 6, respectively) posed high risks to the ecosystem (risk quotient > 1). Priority attention should be paid to the ecological risk posed by these pesticides. Thirty-seven samples had concentrations of individual target analytes over 100 ng/L and four samples had cumulative concentrations of the target analytes over 500 ng/L, exceeding the European Commission guideline values. Taken together, our findings demonstrate a widespread occurrence of the NNIs, agricultural fungicides, and their TPs in the mainstream of the Yangtze River and potential ecological risks posed by some of them.

Short-term effects of the strobilurin fungicide dimoxystrobin on zebrafish gills: A morpho-functional study

Strobilurins represent the most widely used class of fungicides nowadays andare considered relatively non-toxic to mammals and birds but highly toxic to aquatic biota. Dimoxystrobin is one of the novel strobilurins, recently included in the 3rd Watch List of the European Commission as available data indicate that it could pose a significant risk to aquatic species. As yet, the number of studies explicitly assessing the impact of this fungicide on terrestrial and aquatic species is extremely low, and the toxic effects of dimoxystrobin on fish have not been reported. Here we investigate for the first time the alterations induced by two environmentally relevant and very low concentrations of dimoxystrobin (6.56 and 13.13 μg/L) in the fish gills. morphological, morphometric, ultrastructural, and functional alterations have been evaluated using zebrafish as a model species. We demonstrated that even short-term exposure (96 h) to dimoxystrobin alters fish gills reducing the surface available for gas exchange and inducing severe alterations encompassing three reaction patterns: circulatory disturbance and both regressive and progressive changes. Furthermore, we revealed that this fungicide impairs the expression of key enzymes involved in osmotic and acid-base regulation (Na⁺/K⁺-ATPase and AQP3) and the defensive response against oxidative stress (SOD and CAT). The information presented here highlights the importance of combining data from different analytical methods for evaluating the toxic potential of currently used and new agrochemical compounds. Our results will also contribute to the discussion on the suitability of mandatory ecotoxicological tests on vertebrates before the introduction on the market of new compounds.

Occurrence, fate, seasonal variability, and risk assessment of twelve triazine herbicides and eight related derivatives in source, treated, and tap water of Wuhan, Central China

Triazine herbicides have been widely used, are frequently detected in aqueous environments and soils, and can cause acute or chronic toxicity to living organisms. We collected source water samples (n = 20) originating from the Hanshui River and the Yangtze River of Wuhan section, treated water samples (n = 20), and tap water samples (n = 169) in Wuhan, Central China during 2019 for determination of twelve triazine herbicides and their eight derivatives (collectively defined as TZs) and characterizing their fate during water treatment. Eighteen of the twenty TZs were detected in the source water. Atrazine (ATZ) had the highest concentrations (median: 22.4 ng/L) in the source water samples while DACT had the highest concentrations (median: 31.4 ng/L) in the treated water. "Tryns" (ametryn, prometryn, simetryn, terbutryn) were efficiently removed by conventional water treatment, while other target analytes were not; interestingly, hydroxypropazine and prometon increased significantly accompanied by prometryn disappearance, which implicated potential transformation pathways. In addition, "tryns" might be transformed into "tons" (atraton, prometon, secbumeton, terbumeton) by ozonation. In the tap water samples, diaminochlorotriazine had the highest concentrations (median: 34.9 ng/L) among the target analytes, followed by ATZ (18.3 ng/L), hydroxyatrazine (5.17 ng/L), deethylatrazine (5.00 ng/L), hydroxypropazine (3.20 ng/L), deisopropylatrazine (2.05 ng/L), hydroxydesethylatrazine (1.68 ng/L), and others. The TZs had the highest cumulative concentration in July in the tap water samples (median: 89.7 ng/L). This study found that ozonation in combination with activated carbon was more efficient in removing triazine herbicides, although "tryns" could also be transformed during conventional treatment. Ecological risk assessment showed moderate risks posed by hydroxyterbuthylazine, prometryn, and simetryn; the Hanshui River had higher risks than the Yangtze River, and July had higher risks than February. Human exposure to the TZs via water ingestion was low compared to the reference doses. This study characterized the occurrence of some new emerging TZs in the source water, their fate during drinking water treatment, and their seasonal variability in the tap water.

Catalytic degradation of dimethomorph by nitrogen-doped rice husk biochar

N-doped biochar is widely used for activating persulfate to degrade organic pollutants. Which type of N atom is the key factor for activation is still unclear and needs to be further explored and analyzed. In this study, four kinds of biochar were prepared using urea and rice husk as precursors, and tested for the catalytic degradation of dimethomorph. Increasing the nitrogen doping level caused the catalytic removal efficiency of dimethomorph in the presence of peroxymonosulfate increased from 16.6% to 86.8%. A correlation analysis showed that the ability of N-doped biochar to activate PMS is mainly related to the content of pyrrole N, graphite N and carbonyl and the degree of defects. In experiments on electron paramagnetic resonance and free radical suppression, the reactive species of SO₄^•-, ¹O₂,·OH and O₂^.- were detected, among which ¹O₂ was found to be the main agent in the nonradical pathway. The degradation pathways for dimethomorph were analyzed based on a total of 8 degradation products identified by high-performance liquid chromatography-time of flight mass spectrometry (HPLC-Q-TOFMS). The results of this study provide a fundamental basis for using agricultural waste to produce inexpensive and efficient nonmetal catalysts that are highly effective in reducing dimethomorph levels in agricultural lands.

Efficient Adsorption of Tebuconazole in Aqueous Solution by Calcium Modified Water Hyacinth-Based Biochar: Adsorption Kinetics, Mechanism, and Feasibility

The application of fungicides (such as tebuconazole) can impose harmful impacts on the ecosystem and humans. In this study, a new calcium modified water hyacinth-based biochar (WHCBC) was prepared and its effectiveness for removing tebuconazole (TE) via adsorption from water was tested. The results showed that Ca was loaded chemically (CaC₂O₄) onto the surface of WHCBC. The adsorption capacity of the modified biochar increased by 2.5 times in comparison to that of the unmodified water hyacinth biochar. The enhanced adsorption was attributed to the improved chemical adsorption capacity of the biochar through calcium modification. The adsorption data were better fitted to the pseudo-second-order kinetics and the Langmuir isotherm model, indicating that the adsorption process was dominated by monolayer adsorption. It was found that liquid film diffusion was the main rate-limiting step in the adsorption process. The maximum adsorption capacity of WHCBC was 40.5 mg/g for TE. The results indicate that the absorption mechanisms involved surface complexation, hydrogen bonding, and π-π interactions. The inhibitory rate of Cu²⁺ and Ca²⁺ on the adsorption of TE by WHCBC were at 4.05-22.8%. In contrast, the presence of other coexisting cations (Cr⁶⁺, K⁺, Mg²⁺, Pb²⁺), as well as natural organic matter (humic acid), could promote the adsorption of TE by 4.45-20.9%. In addition, the regeneration rate of WHCBC was able to reach up to 83.3% after five regeneration cycles by desorption stirring with 0.2 mol/L HCl (t = 360 min). The results suggest that WHCBC has a potential in application for removing TE from water.

Occurrence, spatiotemporal dynamics, and ecological risk of fungicides in a reservoir-regulated basin

As an indispensable type of pesticide, fungicides have been somewhat neglected compared to insecticides and herbicides. Heavy fungicide application in agricultural regions may generate downstream ecological concerns via in-stream transport, and the reservoir complicates the process. Monitoring fungicide exposure and exploring reservoir effect on fungicide transport is the key to develop the downstream strategies of agricultural diffusion pollution control. Here, we investigated the exposure, spatiotemporal dynamics, and ecological risk of fungicides in a reservoir-regulated agricultural basin, located in the middle of the Yangtze River Basin, China. Seven fungicides were preliminarily identified and exhibited high detection frequencies (>85 %) in subsequent quantification of water samples from three sampling activities. The total concentration of fungicides ranged from 2.47 to 560.29 ng/L, 28.35 to 274.69 ng/L, and 13.61 to 146.968 ng/L in April, September, and November, respectively. Overall, the contamination levels of fungicides were in the ascending order of April < November < September. The spatial distribution of fungicides was closely associated with the dense of cultivated land, supporting its agricultural source. Furthermore, the reservoir plays a retention role in fungicides, alleviating ecological pressure downstream during the water storage period. Yet, due to the alternation of "source" and "sink" function of the reservoir, the contribution of Zijiang River to the fungicide load in the Yangtze River Basin still needs further attention. Although there is no acute risk posed by fungicides, even in the high-exposure scenario, the chronic ecological risk could not be ignored. Agricultural intensive regions, coupled with the reservoir, provide rather substantial chronic ecological concerns. Carbendazim has been designated as a priority pollutant that contributes significantly to cumulative chronic risk. Thus, we emphasize strengthening the supervision of fungicides in surface water and rationally restricting the use of carbendazim in agricultural operations.

Photodegradation of enestroburin in water by simulated sunlight irradiation: Kinetics, isomerization, transformation products identification and toxicity assessment

Enestroburin is the first strobilurin fungicide developed by China and has been widely used to control fungal disease for 15 years. Investigation of its photolytic behaviour is essential for the comprehensive evaluation of its ecological risk. The effects of solution pH, humic acid (HA) and Fe(III) ions on photolysis were studied. The direct photolysis rates of enestroburin in the acidic solution (pH = 4) was faster than that in the basic (pH = 7) or neutral condition (pH = 9). HA and Fe³⁺ ions inhibited photolysis by the light screening effect. The photolysis of enestroburin was very fast due to the generation of photo-isomers. Seven isomeric products of enestroburin were observed using SFC-MS/MS, and the reaction mechanism for photo-induced isomers was proposed. The reaction occurred on three double bonds, including tautomerism of enol ether and oxonium and the triplet energy transfer of the CC and CN double bond. 12 transformation products (TPs) were identified by screening suspect compounds and non-target compounds, and one product (M-381) was synthesized for confirmation and quantification. A probable transformation mechanism was suggested based on the identified TPs and DFT calculations. The main transformation reactions included hydration, hydrolysis, oxidation, reduction and decarboxylation. Finally, the toxicities of the identified TPs and parent compound to aquatic organisms were predicted using ECOSAR software, and the toxicities of enestroburin and M-381 to daphnia magna were tested in the laboratory. The toxicity classification proposed by ECOSAR is reliable to a certain extent. Enestroburin and 2 TPs (M-313 and M-327) were classified as "very toxic", which may pose a potential threat to aquatic ecosystems.

Adverse effects of SYP-3343 on zebrafish development via ROS-mediated mitochondrial dysfunction

As a newly-invented and highly-efficiency strobilurin fungicide, pyraoxystrobin (SYP-3343) has been recognized as a highly poisonous toxin for a variety of aquatic organisms. Nevertheless, the developmental toxicity and potential mechanism of SYP-3343 have not been well-documented. The results showed that SYP-3343 was relatively stable and maintained within the range of 20 % in 24 h, and the LC₅₀ value to embryos at 72 hpf was 17.13 μg/L. The zebrafish embryotoxicity induced by 1, 2, 4, and 8 μg/L SYP-3343 is demonstrated by repressive embryo incubation, enhancive mortality rate, abnormal heart rate, malformed morphological characteristic, and impaired spontaneous coiling, indicating SYP-3343 mostly exerted its toxicity in a dose- and time-dependent manner. Besides SYP-3343 was critically involved in regulating cell cycle, mitochondrial membrane potential, and reactive oxygen species production as well as zebrafish primary cells apoptosis, which can be mitigated using antioxidant N-acetyl-L-cysteine. A significant change occurred in total protein content, the biochemical indices, and antioxidant capacities owing to SYP-3343 exposure. Additionally, SYP-3343 altered the mRNA levels of heart development-, mitochondrial function-, and apoptosis-related genes in zebrafish embryos. These results indicated that SYP-3343 induced apoptosis accompanying reactive oxygen species-initiated mitochondrial dysfunction in zebrafish embryos.

Occurrence of azole and strobilurin fungicides in indoor dust from three cities of China

Widespread use of fungicides has raised the concern of exposure to them among the general population. However, there are extremely limited studies reporting the occurrence of fungicides in indoor dust in China. This study aimed to determine ten agricultural fungicides in indoor dust samples collected in three cities of China from 2016 to 2019, assess spatial and seasonal variations, and estimate the related exposure via dust ingestion. Six out of ten fungicides including difenoconazole, prochloraz, tebuconazole, tricyclazole, azoxystrobin, and pyraclostrobin were frequently detected in the dust samples (ranged 65.8-97.7%) and the concentrations of some fungicides showed a strong correlation with each other. Difenoconazole was the most abundant one among the selected fungicides. The highest level of the selected fungicides was observed in the indoor dust collected from Wuhan in summer 2019 (median cumulative concentration of the fungicides: 62.6 ng/g), while the relatively low concentrations of fungicides were found in the dust from Taiyuan (2.08 ng/g). Heavier fungicide contamination was observed in urban districts compared to that in rural districts. Seasonal variations in the fungicide residuals were also identified. The exposure assessment suggested that intake of the selected fungicides via dust ingestion was much lower than dietary intake reported in other studies. This study filled the data gap of fungicide residuals in the indoor dust in China and further studies are needed to identify the sources and determinants of indoor fungicide contamination.