Optimizing Analysis Methods: Rapid and Accurate Determination of Cuaminosulfate Residues with LC-MS/MS Based on Box-Behnken Design Study.

In view of the defects in the previous detection of cuaminosulfate, which only focused on the analysis of copper ions, there is currently no analysis method available to determine the actual state of cuaminosulfate as chelated or bound. In order to investigate the dissipation and terminal residues in soil and watermelon of cuaminosulfate for food safety and environmental risk, a highly effective technique was developed to detect cuaminosulfate residues in watermelon and soil, and field experiments were conducted in China. After single-factor experiments, residual cuaminosulfate in samples was extracted by pure water, purified using a liquid-liquid approach combined with a dispersive solid-phase extraction, and detected by liquid chromatography tandem mass spectrometry (LC-MS/MS). The Box-Behnken design (BBD) study was used to find the optimal solutions for the time of liquid-liquid purification, the amount of extraction solvent, and the amounts of cleanup sorbents for the analytical method. The average recovery of the method was in the range of 80.0% to 101.1%, the average relative standard deviation (RSD) was 5.3-9.9%, and the detection limit was lower than 0.05 mg/kg. The BBD study not only improved the extraction rate of the method, but also saved time and was operated easily. The final residues of cuaminosulfate in watermelon at different sampling intervals were all lower than 0.05 mg/kg under field conditions. The cuaminosulfate in soils dissipated following exponential kinetics, with half-life values in the range of 9.39 to 12.58 days, which varied by different locations. Based on the validated method, food safety residues and soil residues can be determined rapidly and accurately.

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.

Spontaneous In-Source Fragmentation Reaction Mechanism and Highly Sensitive Analysis of Dicofol by Electrospray Ionization Mass Spectrometry.

Although dicofol has been widely banned all over the world as a kind of organochlorine contaminant, it still exists in the environment. This study developed a high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS) detection technique for dicofol, an environmental pollutant, for the first time using in-source fragmentation. The results confirmed that m/z 251 was the only precursor ion of dicofol after in-source fragmentation, and m/z 139 and m/z 111 were reasonable product ions. The main factors triggering the in-source fragmentation were the H+ content and solution conductivity when dicofol entered the mass spectrometer. Density functional theory can be used to analyze and interpret the mechanism of dicofol fragmentation reaction in ESI source. Dicofol reduced the molecular energy from 8.8 ± 0.05 kcal/mol to 1.0 ± 0.05 kcal/mol, indicating that the internal energy release from high to low was the key driving force of in-source fragmentation. A method based on HPLC-MS/MS was developed to analyze dicofol residues in environmental water. The LOQ was 0.1 µg/L, which was better than the previous GC or GC-MS methods. This study not only proposed an HPLC-MS/MS analysis method for dicofol for the first time but also explained the in-source fragmentation mechanism of compounds in ESI source, which has positive significance for the study of compounds with unconventional mass spectrometry behavior in the field of organic pollutant analysis and metabonomics.

Quizalofop-P-ethyl induced developmental toxicity and cardiotoxicity in early life stage of zebrafish (Danio rerio).

Quizalofop-P-ethyl (QpE), a highly efficient selective herbicide, has good control effect on annual and perennial weeds. However, its excessive use will pose a threat to the ecological environment. QpE has been proven harmful to aquatic organisms, but there is little evidence on the adverse effects of QpE in the early life of aquatic organisms. In this work, zebrafish (Danio rerio) embryos were treated with 0.10, 0.20, 0.30, 0.40, and 0.50 mg/L of QpE for 120 h. The findings revealed that the LC50 value of QpE to zebrafish embryos was 0.23 mg/L at 96 hpf. QpE exposure significantly increased the mortality rate, decreased the hatching rate and caused morphological defects during zebrafish embryonic development, with a concentration dependent manner. QpE also caused severe morphological changes in the cardiovascular system, as well as resulted in a dysfunction in cardiovascular performance. Meanwhile, both histopathological examination and neutrophil observations showed inflammatory response occurred in the heart. Furthermore, several genes associated with heart development and inflammation were significantly altered following QpE exposure. A protein-protein interaction (PPI) network analysis proved that there was a connection between the changed heart development-relevant and inflammation-related genes. Taken together, our findings suggest that QpE causes cardiotoxicity in zebrafish embryos by altering the expression of genes in the regulatory network of cardiac development, which might be aggravated by inflammatory reactions, thereby affecting embryo development. These findings generated here are useful for in-depth assessment of the effects of QpE on early development of aquatic organisms and providing theoretical foundation for risk management measures.

Echingridimer A, an Oxaspiro Dimeric Sesquiterpenoid with a 6/6/5/6/6 Fused Ring System from Echinops grijsii and Aphicidal Activity Evaluation.

A new dimeric eudesmane sesquiterpenoid with an unreported 6/6/5/6/6 fused carbon skeleton, echingridimer A (1), and five monomers (2-6), including two new compounds (2 and 3), were isolated from the roots of Echinops grijsii. Their structures and absolute configurations were elucidated by comprehensive spectroscopic analyses and confirmed by X-ray crystallography or electronic circular dichroism spectra. Compound 1 represents the first example of a 3,15'-linked Michael-type adduct of two eudesmanes, which feature a unique 1-oxaspiro[4.5]decan moiety. The plausible biogenetic pathway for 1-6 was briefly discussed. The oxaspiro dimer (1) not only showed stronger aphicidal activity than closely related monomeric compounds (2-6) and the commercial aphicide pymetrozine but also exhibited remarkable insecticide activity against a broad range of aphids, thus could be used as a potential biobased insecticide to suppress aphids.

Mitochondria response to camptothecin and hydroxycamptothecine-induced apoptosis in Spodoptera exigua cells.

Camptothecin (CPT), a natural alkaloid extracted from Camptotheca acuminata Decne, exhibits potential insecticidal activities against various insect species. Our previous studies have showed that CPTs induced apoptosis in Spodoptera exigua Hübner cell line which is mediated preliminarily by the mitochondrial pathway. In this study, changes of mitochondrial morphologic and function were investigated to characterize mitochondrial responses in CPTs induced apoptosis. After incubation IOZCAS-Spex-II cells with CPT and HCPT, mitochondria exhibited obvious changes in the size, morphology and distribution, and ultrastructural alterations characterized by disruption of cristae and membrane. The typical characteristics of apoptosis, including chromatin condensation, nucleus shrivels, and cytoplasmic vacuoles were found. CPT and HCPT induced IOZCAS-Spex-II cell apoptosis accompanied with increased dramatically cytosolic Ca2+ and reduced mitochondrial membrane potential in the dose and time-dependent pattern. Cytochrome c release induced by CPT and HCPT was partially reduced in the presence of CsA, which suggested that the opening of mitochondrial permeability transition pore. Taken together, these results suggested the role of mitochondria in regulation of insect cell apoptosis, which provided the basic information for illustrating the apoptosis pathway in insects and for using reasonably CPTs to control insect pests.

Synthesis, insecticidal activity and inhibition on topoisomerase I of 20(S)-t-Boc-amino acid derivatives of camptothecin.

Camptothecin (CPT), a quinolone alkaloid extracted from Camptotheca acuminata Decne, exhibits potential insecticidal activities against various insect species. Our previous studies have showed that CPT induced apoptosis in Spodoptera exigua Hübner cell line and inhibited the relaxation activity of topoisomerase I (Topo I). In this study, total seven 20(S)-t-butoxy carbonyl-amino acid derivatives of CPT were synthesized and evaluated for insecticidal activities, cytotoxicity and Topo I inhibitory activities. Results showed that introduction of t-Boc amino acids to 20-position on CPT improves contact assay and cytotoxicity of most derivatives toward S. exigua but reduces inhibitory effect on relaxation activity of S. exigua Topo I. Furthermore, compounds 1d and 1g demonstrated higher level of contact activities and cytotoxicity than CPT and hydroxyl-camptothecin (HCPT), which are potential to be developed as potential insecticides targeted at more than Topo I.

Emission reduction of 1,3-dichloropropene by soil amendment with biochar.

Soil fumigation is an important treatment in the production chain of fruit and vegetable crops, but fumigant emissions contribute to air pollution. Biochar as a soil amendment has shown the potential to reduce organic pollutants, including pesticides, in soils through adsorption and other physicochemical reactions. A laboratory column study was performed to determine the effects of soil applications of biochar for reducing emissions of the fumigant 1,3-dichloropropene (1,3-D). The experimental treatments comprised of unamended and amended with biochar at doses of 0, 0.5, 1, 2, and 5% (w/w) in the top 5 cm soil layer. The unamended treatment resulted in the highest emission peak flux at 48 to 66 µg m s. Among the biochar amendment treatments, the highest peak flux (0.83 µg m s) was found in the biochar 0.5% treatment. The total emission loss was 35.7 to 40.2% of applied for the unamended treatment and <0.1 to 2.9% for the biochar-amendment treatments. A germination bioassay with cucumber seeds showed that ≥7 d of aeration would be needed to avoid phytotoxicity before replanting in biochar-containing fumigated soil. The results indicate that treatments with 0.5% or more biochar amendment reduced emission peak flux by >99.8% and showed total 1,3-D emission loss by >92% compared with that without biochar. The amendment of surface soil with biochar shows a great potential for reducing fumigant emissions.

Control of Soilborne Pathogens of Zingiber officinale by Methyl Iodide and Chloropicrin in China.

Development of effective alternative soil fumigants is essential to the phasing out of methyl bromide (MeBr) while keeping major soilborne pathogens under control. Here, we report on the laboratory studies and field trials evaluating methyl iodide (MeI) and chloropicrin (Pic) for control of major soilborne ginger (Zingiber officinale) pathogens Ralstonia solanacearum, Pythium spp., Fusarium oxysporum, and Meloidogyne incognita in Shandong province of China. Laboratory studies indicated that MeI at 24 mg/kg of soil was most effective, reducing four pathogens by >90%. Treatments with MeI+Pic at 12 mg/kg (1:3 and 1:5) also reduced these pathogens by >82%. In the field trials, MeI at 30 or 40 g/m2 and MeI+Pic (1:3) at 40 g/m2 yielded excellent long-term control of all target pathogens. These treatments allowed ginger plants to maintain vigorous growth and produce a greater number of tillers (>12 per plant), and increased ginger yields by >80% compared with the nontreated controls. MeI at a reduced rate of 20 g/m2 or Pic at 40 g/m2 provided levels of disease control similar to MeBr. These studies demonstrated that injection treatments with MeI at 30 and 40 g/m2, and MeI+Pic (1:3) at 40 g/m2, followed by covering with virtually impermeable film, are effective alternatives of soil fumigation for control of the major ginger pathogens in Shandong.

Joint toxic mechanism of clothianidin and prochloraz in the earthworm (Eisenia fetida).

Pesticides are typically present as combinations within soil ecosystems and have detrimental effects on untamed surroundings. However, the collective impacts and fundamental mechanisms of pesticides on soil living beings are currently inadequately assessed. In our current work, we evaluated the interactive consequences of clothianidin (CLO) and prochloraz (PRO) on earthworms (Eisenia fetida) using several toxicological tests, such as acute adverse effects, biocatalytic activity, and alterations in transcriptional activity. The findings revealed that CLO (with a 14-day LC50 value of 6.08 mg kg-1) exhibited greater toxicity compared to PRO (with a 14-day LC50 value of 79.41 mg kg-1). Moreover, the combinations of CLO and PRO had synergistic acute effects on E. fetida. Additionally, the activities of POD, CAT, and GST were significantly varied in most instances of single and mixed treatments when compared to the control. Surprisingly, the transcriptional levels of four genes (gst, sod, crt, and ann), related to oxidative load, metabolic detoxification systems, endoplasmic reticulum, and oxytocin neuropeptide, respectively, were also altered in response to single and mixture exposures, as compared to the control. Alterations in enzyme activity and gene transcriptional level could serve as early indicators for detecting co-exposure to pesticides. The findings of this research offered valuable holistic understanding regarding the toxicity of pesticide combinations on earthworms. Further research should be conducted to investigate the persistent effects of pesticide mixtures on terrestrial invertebrates in order to draw definitive conclusions about the associated risks.

Adsorption of acetochlor-contaminated water systems using novel P-doped biochar: Effects, application, and mechanism.

Given the serious threat of acetochlor (ACT) to the aquatic ecological environment, designing wastewater treatment-oriented adsorbents for the sustainable remediation of actual ACT-contaminated water is a promising yet challenging strategy. Herein, a novel P-doped biochar (PBC-800) with a high adsorption capacity (51.34 mg g-1) and a rapid reaction rate (47.35 mg g-1 h-1) for ACT was prepared through pyrolyzing of rice straw biomass pre-impregnated with potassium dihydrogen phosphate (KH2PO4). Additionally, P-doped biochars synthesized at different pyrolysis temperatures exhibited significant variations in ACT adsorption performance, which was mainly ascribed to the distinction between hydrophilicity and sp2 conjugate C (ID/IG = 0.84-1.08). The adsorption behavior of ACT on PBC-800 followed the Elovich kinetics and Freundlich adsorption isotherm models. Thermodynamic calculations indicated that the adsorption of ACT by PBC-800 was a spontaneously disordered decreasing exothermic process. Besides, PBC-800 exhibited a powerful anti-interference for ACT adsorption within complex water matrices, highlighting its potential for various of practical applications. Through characterization analysis and further experiments, it was proved that the excellent adsorption performance of PBC-800 on ACT was ascribed to a combination of physical and chemical adsorption mechanisms, including 57.5% pore filling, 23.4% hydrophobic interaction, 12.7% π-π interaction, and 6.4% hydrogen bonding. Moreover, PBC-800 exerted a prominent adhesion impact upon Gram-positive and negative bacteria at 3 h. This study offers a new idea for the utilization of agricultural residues and provides insights into the mechanism of ACT adsorption through its derived biochar.

Integrate transcriptomic and metabolomic analysis reveals the underlying mechanisms of behavioral disorders in zebrafish (Danio rerio) induced by imidacloprid.

Imidacloprid, a widely used neonicotinoid insecticide, poses a significant threat to aquatic ecosystems. Behavior is a functional indicator of the net sensory, motor, and integrative processes of the nervous system and is presumed to be more sensitive in detecting toxicity. In the present study, we investigated the behavioral effects of imidacloprid at the level of environmental concentrations (1, 10 and 100 µg/L) for a constant exposure to zebrafish adults, and performed the integrated transcriptomic and metabolomic analysis to analyze the molecular mechanism underlying behavioral effects of imidacloprid. Our results show that imidacloprid exposure significantly induce behavioral disruptions characterized by anxiety, depression, and reduced physiological function including exploratory, decision, social interaction and locomotor activity. Integrated transcriptomic and metabolomic analysis indicate that the disruption of circadian rhythm, metabolic imbalance of arginine and proline, and neurotransmitter disorder are the underlying molecular mechanisms of behavioral impairment induced by imidacloprid. The "gene-metabolite-disease" network consisted by 11 metabolites and 15 genes is associated human disease Alzheimer's disease (AD) and schizophrenia. Our results confirm the behavioral impairment induced by imidacloprid at environmental concentrations for constant exposure. The identified genes and metabolites can be used not only to illustrate the underlying mechanisms, but also can be developed as biomarkers in determining the ecological risk of imidacloprid to aquatic organisms even Homo sapiens.

Bioavailability evaluation of epoxiconazole and difenoconazole in rice and the influence of dissolved organic matter in reducing uptake and translocation.

The aim of this study was to assess the bioavailability of epoxiconazole (EPO) and difenoconazole (DIF) in rice plants by evaluating their uptake, translocation, and accumulation. The results showed that the concentration of DIF in the roots was approximately three times higher than EPO, and both accumulated mainly in the roots. In addition, EPO continued to be transported from stems to leaves, causing a rise in its concentration in leaves. Contrastingly, only a minimal amount of DIF was transported to the leaves. This phenomenon is mainly governed by their differing octanol-water partition coefficient. The effects of dissolved organic carbon (DOC) on the accumulation of EPO and DIF in the roots were similar to those of the freely dissolved concentration measured by OECAMs. The concentrations of EPO and DIF in the roots and OECAMs consistently decreased with increasing DOC levels. Furthermore, a significant linear relationship was observed between the EPO and DIF concentrations in root and OECAMs. We also confirmed the accuracy and usefulness of the OECAMs method in predicting the bioavailability of EPO and DIF in rice roots. Therefore, OECAMs show good potential for use as a passive sampler to evaluate the bioavailability of EPO and DIF.

Combined ecotoxicological effects of different-sized polyethylene microplastics and imidacloprid on the earthworms (Eisenia fetida).

Microplastics (MPs) and pesticides frequently coexist in farmland soil; however, there are relatively few studies on the ecological risk assessment of soil animals attributed to the combined pollution caused by MPs and pesticides. Moreover, the influence of particle size on the combined toxic effects of MPs and pesticides remains poorly understood. In this study, different-sized polyethylene MPs (PE MPs; 10 µm, 500 µm, and 2 mm) were combined with a series of imidacloprid concentrations (IMI; 0.10, 0.50 and 1.00 mg/kg), and earthworms (Eisenia fetida) were exposed to these MP and IMI combinations for 28 d to explore the combined toxic effects and mechanisms. The results showed, compared with IMI or PE MPs exposure alone, the combined exposure of IMI and PE MPs did not substantially increase the acute toxicity of earthworms but significantly inhibited weight increase and induced more serious epidermal damage to earthworms with a size effect; among these 10 µm PE MPs combined with IMI exhibited the strongest toxic effects. In addition, the combined exposure decreased antioxidant enzymes activity and caused oxidative damage in earthworms. Transcriptome results demonstrated most of the treatment combinations affected the ferroptosis pathway, which was further verified by the increase in the total iron content, reactive oxygen species, and malondialdehyde content in earthworms. Combined with the analysis of key signalling pathways, the above results revealed that the combined exposure to IMI and PE MPs showed stronger toxicity to earthworms than exposure to either IMI or MPs alone, which was mediated by the superimposed effect of ferroptosis and oxidative damage. Moreover, the effect was size-dependent, with 10 µm PE MPs combined with IMI exhibiting the strongest toxic effects. This study aimed to provide data to support the ecological risk assessment of soil animals caused by the combined pollution of MPs and coexisting pesticides.

Bioavailability assessment of difenoconazole to earthworms (Eisenia fetida) in soil by oleic acid-embedded cellulose acetate membrane.

Passive sampling technology is widely used to evaluate the bioavailability of pollutants. However, relatively few studies have used passive sampling membranes (PSMs) to evaluate the environmental risks of pollutants in soil, particularly pesticides. Here, the bioavailability of difenoconazole to earthworms (Eisenia fetida) was evaluated using an oleic acid-embedded cellulose acetate membrane (OECAM) for the first time. Difenoconazole reached 94 % equilibrium (T94%) within 1 d in OECAM. For soil pore water, the freely dissolved concentration (Cfree) of difenoconazole was determined using OECAM (R2 = 0.969). In the soil system, a strong linear correlation between the difenoconazole concentration in OECAM and earthworms was observed (R2 = 0.913). The bioavailability of difenoconazole was affected by the soil type and biochar content. The higher the content of soil organic matter and biochar, the lower the concentration of difenoconazole in earthworms, OECAM, and soil pore water. The concentrations of difenoconazole in pore water, earthworms, and OECAM decreased by 65.3, 42.0, and 41.6 %, respectively, when 0.5 % biochar was added. Difenoconazole mainly enters OECAM and earthworms through passive diffusion with similar uptake pathways. Therefore, the bioavailability of difenoconazole to earthworms in different soils can be evaluated using the OECAM.

Abiotic transformation of kresoxim-methyl in aquatic environments: Structure elucidation of transformation products by LC-HRMS and toxicity assessment.

In this study, abiotic transformation of an important strobilurin fungicide, kresoxim-methyl, was investigated under controlled laboratory conditions for the first time by studying its kinetics of hydrolysis and photolysis, degradation pathways and toxicity of possibly formed transformation products (TPs). The results indicated that kresoxim-methyl showed a fast degradation in pH9 solutions with DT50 of 0.5 d but relatively stable under neutral or acidic environments in the dark. It was prone to photochemical reactions under simulated sunlight, and the photolysis behavior was easily affected by different natural substances such as humic acid (HA), Fe3+and NO3-which are ubiquitous in natural water, showing the complexity of degradation mechanisms and pathways of this chemical compound. The potential multiple photo-transformation pathways via photoisomerization, hydrolyzation of methyl ester, hydroxylation, cleavage of oxime ether and cleavage of benzyl ether were observed. 18 TPs generated from these transformations were structurally elucidated based on an integrated workflow combining suspect and nontarget screening by high resolution mass spectrum (HRMS), and two of them were confirmed with reference standards. Most of TPs, as far as we know, have never been described before. The in-silico toxicity assessment showed that some of TPs were still toxic or very toxic to aquatic organisms, although they exhibit lower aquatic toxicity compared to the parent compound. Therefore, the potential hazards of the TPs of kresoxim-methyl merits further evaluation.

Factors impacting the behavior of phytoremediation in pesticide-contaminated environment: A meta-analysis.

Phytoremediation provides substantial advantages, including eco-friendliness, cost-effectiveness, efficiency, and visual appeal. However, the current knowledge of the factors influencing phytoremediation in pesticide-contaminated environments remains limited. It is critical to understand phytoremediation and the factors affecting the variation in removal efficiency. In this study, we compiled 72 previous research articles to quantify plant-induced improvements in removal efficiency and identify factors that influence variations in phytoremediation behavior through meta-analysis. We observed a significant increase in the removal efficiency of phytoremediation compared to the control group which did not involve phytoremediation. Pesticides significantly affect removal efficiency in terms of their modes of action, substance group, and properties. Plants demonstrated higher efficiency in remediating environments contaminated with pesticides possessing lower molecular masses and log Kow values. Plant species emerged as a crucial determinant of variations in removal efficiency. Annual plants exhibited a 1.45-fold higher removal efficiency than perennial plants. The removal efficiencies of different plant types decreased in the following order: agri-food crops > aquatic macrophytes > turfgrasses > medicinal plants > forage crops > woody trees. The Gramineae family, which was the most prevalent, demonstrated a robust and consistent phytoremediation ability. This study offers a more comprehensive triangular relationship between removal efficiency, pesticides, and plants, expanding the traditional linear model. Our findings offer valuable insights into the behavior of phytoremediation in pesticide-contaminated environments and the factors determining its success, ultimately guiding further research toward developing strategies for higher removal efficiency in phytoremediation.

Mixture toxicity of pyraclostrobine and metiram to the zebrafish (Danio rerio) and its potential mechanism.

The interplay between pesticides plays a critical role in ecotoxicology since these chemicals rarely emerge as single substances but rather in mixtures with other chemicals. In the present work, we purposed to clarify the combined toxic impacts of pyraclostrobine (PYR) and metiram (MET) on the zebrafish by using numerous indicators. Results exhibited that the 4-day LC50 value of MET to fish embryos was 0.0025 mg a.i. L-1, which was lower compared with PYR (0.019 mg a.i. L-1). Combinations of PYR and MET presented a synergetic impact on fish embryos. Contents of POD, CYP450, and VTG were drastically increased in the plurality of the single and joint treatments relative to the baseline value. Three genes, including vtg1, crh, and il-8, related to the endocrine and immune systems, were also surprisingly up-regulated when fish were challenged by the individual and mixture pesticides compared with the baseline value. These results afforded valuable information on the latent toxicity mechanisms of co-exposure for PYR and MET in the early growth stage of fish. Moreover, our data also revealed that frequent application of these two pesticides might exert a potentially ecotoxicological hazard on aquatic ecosystems. Collectively, the present study provided valuable guidance for the risk evaluation of chemical combinations.

Developmental defects and potential mechanisms in F1 generation of parents exposed to difenoconazole at different life stages of zebrafish (Danio rerio).

As a typical triazole fungicide, difenoconazole is extensively used to control plant diseases; however, its residue in environmental waters poses a risk to aquatic organisms. In this study, we investigated the acute toxicity of different life stages and sub-lethal toxicity in embryonic yolk sac stage of difenoconazole to zebrafish, and the developmental toxicity in F1 generation of parents exposed to difenoconazole at different life stages of zebrafish. Furthermore, we used transcriptomics to explore the potential mechanisms of difenoconazole on the F1 larvae of parents exposed to the chemical at the embryonic stage. The results of this study showed that developmental defects were observed in the F1 embryo/larvae of parents exposed to 3, 30, and 300 µg/L of difenoconazole at different (embryo, larval, juvenile, and adult) life stages, and exposure to difenoconazole at the embryonic stage caused more severe developmental toxicity than those at other life stages. Developmental defects (malformation, inhibition of heartbeat and body length) were observed in the F1 embryos and larvae of parents exposed to difenoconazole at the embryonic stage. In addition, the total cholesterol and triglyceride contents were significantly reduced in the F1 larvae, and RNA-seq analysis revealed significant alterations in the expression of nine genes (msmo1, hsd17b7, sc5d, tm7sf2, ebp, cyp2r1, lss, cyp51, and cyp27b1) in the steroid synthesis pathway. This is suggested that F1 larvae of parents exposed to difenoconazole at the embryonic stage show abnormalities in the steroid biosynthetic pathway. These results reveal the differences in toxicity of difenoconazole to zebrafish at different life stages, improve studies on difenoconazole toxicity to zebrafish, and provide a new perspective for assessing the risk of contaminants to aquatic organisms.

Sorption and degradation of prothioconazole and its metabolites in soils and water sediments, and its combinative toxicity to Gobiocypris rarus.

To reduce detrimental effects to the environment, the application of prothioconazole and its metabolites requires comprehensive evaluation, which has been dine for the first time in this study. The behavior of prothioconazole, including degradation and sorption under aerobic and anaerobic conditions, was evaluated in three common soil types and two types of water-sediment systems under different environmental conditions. Individual and joint toxicities of prothioconazole and its metabolites, M01 and M04, on aquatic organisms, including the Gobiocypris rarus, are also investigated in the present study. Under aerobic and anaerobic conditions, the half-life of prothioconazole in the three types of soils ranged from 0.0565 to 2.27 days and 0.138-1.73 days, respectively. Under aerobic conditions, the half-life of prothioconazole in the Hunan paddy area and Beijing Qidu reservoir water-sediment samples were 2.18 and 1.58 days, respectively. In soil and water-sediment samples, prothioconazole degraded to M01 and M04, and the formation rate of M04 was higher than M01 under aerobic condition. M04 and M01 gradually increased to a peak value in soil and water-sediment systems, then decreased over time, while prothioconazole gradually decreased. The half-life of prothioconazole in soils was lower than its metabolites, with the DT50 of metabolites ranging from 16.6 to 99.6 days, 15.8 and 50.7 days for M01 and M04 under aerobic condition, respectively. While the adsorption capacities (Kf values) of M04 and M01 ranged from 2.09 to 88.92 and 8.98 to 243.30 (µg/g)/(mg/L), respectively, in the three soils. Regarding toxicity to aquatic organisms, the metabolites did not show higher toxicity than prothioconazole, except M01 on Gobiocypris rarus. Joint toxicity assays showed that mixtures of prothioconazole with its metabolites exhibited higher toxicity than any compound individually and indicated synergistic interactions could occur at equitoxic ratios and equivalent concentrations. This study provides a comprehensive investigation on the fate and environmental risk posed by prothioconazole.