Hydrolytic products and kinetics of triazophos in buffered and alkaline solutions with different values of pH

Ultralow-background SERS substrates for reliable identification of organic pollutants and degradation intermediates

Chemical methods for preparing SERS substrates have the advantages of low cost and high productivity, but the strong background signals from the substrate greatly limit their applications in characterization and identification of organic compounds. Herein, we developed a one-step synthesis method to prepare silver nanoparticle substrates with ultralow SERS background using anionic ligands as stabilizing agents and applied the SERS substrate for the reliable and reproducible identification of typical organic pollutants and corresponding degradation intermediates. The synthesis method shows excellent universality to different reducing agents cooperating with different anionic ligands (Cl-, Br-, I-, SCN-). As model applications, the machine learning algorithm can realize the precise prediction of six organophosphorus pesticides and eight sulfonamide antibiotics with 100% accuracy based on SERS training data. More importantly, the ultralow-background SERS substrate enables one to detect and identify the time-dependent degradation intermediates of organophosphorus pesticides by combining them with density functional theory (DFT) calculations. All the results indicate that the ultralow-background SERS substrate will greatly push the development of SERS characterization applications.

Characterization of a new chlorimuron-ethyl-degrading strain Cedecea sp. LAM2020 and biodegradation pathway revealed by multiomics analysis

The widespread use of the herbicide chlorimuron-methyl is hazard to rotational crops and causes soil degradation problems. Biodegradation is considered a promising way for removing herbicide residues from the environment. Here, a new isolated strain, Cedecea sp. LAM2020, enabled complete degradation of 100 mg/L chlorimuron-methyl within five days. Transcriptome analysis revealed that ABC transporters, atrazine degradation and purine metabolism were enriched in the KEGG pathway. Integrating GO and KEGG classification with related reports, we predict that carboxylesterases are involved in the biodegradation of chlorimuron-methyl by LAM2020. Heterologous expression of the carboxylesterase gene carH showed 26.67% degradation of 50 mg/L chlorimuron-methyl within 6 h. The intracellular potential biological response and extracellular degradation process of chlorimuron-ethyl were analyzed by the nontarget metabolomic and mass spectrometry respectively, and the biodegradation characteristics and complete mineralization pathway was revealed. The cleavage of the sulfonylurea bridge and the ester bond achieved the first step in the degradation of chlorimuron-methyl. Together, these results reveal the presence of acidolysis and enzymatic degradation of chlorimuron-methyl by strain LAM2020. Hydroponic corn experiment showed that the addition of strain LAM2020 alleviated the toxic effects of chlorimuron-ethyl on the plants. Collectively, strain LAM2020 may be a promising microbial agent for plants chlorimuron-ethyl detoxification and soil biofertilizer.

Novel metabolites of triazophos formed during degradation by bacterial strains Pseudomonas kilonensis MB490, Pseudomonas kilonensis MB498 and pseudomonas sp. MB504 isolated from cotton fields

In the current scenario of overuse of pesticides (resulting in soil and water pollution and ultimately leading to biomagnification), a research project was carried out to study biodegradation of Triazophos. For this purpose, three bacterial strains (Pseudomonas kilonensis MB490, Pseudomonas kilonensis MB498 and Pseudomonas sp. MB504), isolated from cotton fields of Mianwali, Pakistan were investigated for Triazophos degradation and metabolite formation in M-9 broth, soil slurry and soil microcosm after incubation for 9 days. There was 88.4-95.8% Triazophos degradation in M-9 broth, 99.90% degradation in soil slurry and 92.74 to 96% Triazophos degradation in soil microcosm by these bacteria after 9 days. While there was negligible Triazophos degradation (upto 7%) in the controls without bacteria. According to GCMS analysis, 7 unique and novel metabolites (1, 2, 4-Triazole-4-amine, N-(2-Thienylmethyl), Benzene sulfonic acid hydrazide, Benzene sulfonic acid methyl ester, 4H-1,2,4-Triazole-4-benzenesulfonamide, 4, 5 dihydro-N-(O-toyl)-3-furamide, Ethyl 4-phenyldiazenylbenzoate and Dibutyl methanephosphonate) of Triazophos were revealed. Current results strongly suggest the potential of these bacterial strains for the remediation of Triazophos contaminated agricultural soils.

Photocatalytic Degradation of Profenofos and Triazophos Residues in the Chinese Cabbage, Brassica chinensis, Using Ce-Doped TiO2

Pesticides have revolutionized the modern day of agriculture and substantially reduced crop losses. Synthetic pesticides pose a potential risk to the ecosystem and to the non-target organisms due to their persistency and bioaccumulation in the environment. In recent years, a light-mediated advanced oxidation processes (AOPs) has been adopted to resolve pesticide residue issues in the field. Among the current available semiconductors, titanium dioxide (TiO2) is one of the most promising photocatalysts. In this study, we investigated the photocatalytic degradation of profenofos and triazophos residues in Chinese cabbage, Brassica chinensis, using a Cerium-doped nano semiconductor TiO2 (TiO2/Ce) under the field conditions. The results showed that the degradation efficiency of these organophosphate pesticides in B. chinensis was significantly enhanced in the presence of TiO2/Ce. Specifically, the reactive oxygen species (ROS) contents were significantly increased in B. chinensis with TiO2/Ce treatment, accelerating the degradation of profenofos and triazophos. Ultra-performance liquid chromatography–mass spectroscopy (UPLC-MS) analysis detected 4-bromo-2-chlorophenol and 1-phenyl-3-hydroxy-1,2,4-triazole, the major photodegradation byproducts of profenofos and triazophos, respectively. To better understand the relationship between photodegradation and the molecular structure of these organophosphate pesticides, we investigated the spatial configuration, the bond length and Mulliken atomic charge using quantum chemistry. Ab initio analysis suggests that the bonds connected by P atom of profenofos/triazophos are the initiation cleavage site for photocatalytic degradation in B. chinensis.

Environmental behaviors of spirotetramat in water

Spirotetramat is a pesticide with bidirectional systemicity in both xylem and phloem. Currently, researches show that spirotetramat has definite toxicity to aquatic organism. This paper aims to study the environmental behaviors of spirotetramat in water, in the hope of providing guidance for security evaluation of spirotetramat. The researches in this paper showed that under lighting condition, the half-life period of spirotetramat in water was 13.59 days. In water, spirotetramat could be degraded into B-enol and B-keto. As seen from the residual concentrations of two products, B-enol was the dominant degradation product. Under different temperatures, the hydrolysis products of spirotetramat remain B-enol and B-keto. The temperature has little effect on the residual concentration of spirotetramat in water. The residual concentration of B-enol in water gradually increased with the extension of time but B-keto had no significant change. In the buffer solution of different pH values, the degradation rate of spirotetramat was significantly enhanced with the increase of solution pH value. The hydrolysis products of spirotetramat in buffer solution of different pH values were still B-enol and B-keto, and pH exerted certain influence on the residual concentration of B-enol in water. The hydrolysis conversion of spirotetramat has theoretical and practical significance for the safe and reasonable usage of it, as well as for the further evaluation of spirotetramat's ecological risk in water.

Neurotoxic effect of triazophos on goldfish (Carassius auratus) and tissue specific antioxidant responses

Due to the high chemical and photochemical stability, an organophosphorus pesticide triazophos might enter aquatic ecosystems and impose negative effect on aquatic organisms. In order to investigate short-term toxicity of triazophos on goldfish (Carassius auratus), antioxidant response in brain, spleen, kidney and liver was tested in this study. As a confirmation, the impact of triazophos on acetyl cholinesterase (AChE) activity was found a reduction in all studied tissues, especially in brain. In addition, 0.1 and 0.5 mg L(-1) triazophos induced MDA level increased, while glutathione content (GSH), superoxide dismutase (SOD), catalase (CAT) and lactate dehydrogenase (LDH) activities decreased. Of note, more prominent oxidative stress was provoked in kidney and liver, but weaker in brain and spleen. These results revealed that triazophos could cause a generalized oxidative stress and tissue specific antioxidant response in goldfish. Furthermore, neuroendocrine-growth-related gene expression (growth hormone (GH), luteinizing hormone (LH) and peptide YY) in brain was also changed by exposed to triazophos during 4 and 7d exposure periods. Linked with the above results, the present study pointed out that triazophos might induce a neurotoxic effect and oxidative damage in goldfish, and the goldfish brain should be a critical target for triazophos-induced damage.

Toxic effects of triazophos on rare minnow (Gobiocypris rarus) embryos and larvae

Triazophos (TAP) has been widely used in agriculture for controlling insect pests and is a known organophosphorus pesticide. Due to TAP characteristics, such as high chemical and photochemical stability, its potential toxicity to aquatic organisms has gained great interest. To explore the potential developmental toxicity of TAP, Gobiocypris rarus embryos and larvae were exposed to various concentrations of TAP (0.1-15 mg L(-1)) until 72 h. Results showed that values of 72 h LC50 and EC50 were 7.44 and 5.60 mg L(-1) for embryos, 2.52 and 1.37 mg L(-1) for larvae. Increased malformation, decreased heart rate and body length provide a gradual concentration-dependent pattern. Enzyme activities and mRNA levels were significantly changed even at low concentration (0.05 mg L(-1) for embryos and 0.01 mg L(-(1) for larvae). Overall, the present study points out that TAP is likely a risk to the early development of G. rarus. The information presented in this study will be helpful in better understanding the toxicity induced by TAP in fish embryos and larvae.

Isolation, identification and characterization of a novel triazophos-degrading Bacillus sp. (TAP-1)

A novel triazophos-degrading Bacillus sp., TAP-1, was isolated from sewage sludge in a wastewater treating system of organophosphorus pesticide produced by Funong Group Co. in Jianou, Fujian, southeastern China. The isolate is a gram-positive and rod-shaped bacterium capable of hydrolyzing insecticide triazophos and was identified as a strain of Bacillus using polyphasic taxonomy combined with analysis of the morphological and physio-biochemical properties. TAP-1 could degrade triazophos through co-metabolism. When fed with nutrients such as yeast extract, peptone and glucose, TAP-1 could degrade 98.5% of TAP in the medium (100 mg/l) within 5 days. The optimal pH and temperature for the degradation were 6.5-8 and 32°C, respectively. An enzyme distribution experiment showed that the enzyme responsible for TAP degradation appeared to be intracellular.

Electropolymerized molecular imprinting on gold nanoparticle-carbon nanotube modified electrode for electrochemical detection of triazophos

An electrochemical sensor for pesticide triazophos (TAP) was prepared by deposition of gold nanoparticles (AuNPs) on carbon nanotubes (CNTs) modified glassy carbon (GC) electrode surface using a potentiostatic method, followed by electropolymerizing of o-hydroxyphenol at the AuNP/CNT/GC electrode surface in the presence of template triazophos via cyclic voltammetry. The electrochemical response of triazophos at the TAP-imprinted polyhydroxyphenol (PHP) modified AuNP/CNT/GC (PHP/AuNP/CNT/GC) electrode was investigated by cyclic voltammetry. The cyclic voltammetric response of triazophos at the TAP-imprinted PHP/AuNP/CNT/GC electrode was significantly higher than that at bare GC, CNT/GC, AuNP/CNT/GC, imprinted PHP/CNT/GC and non-imprinted PHP/AuNP/CNT/GC electrodes. The results indicated that the TAP-imprinted PHP/AuNP/CNT/GC electrode can effectively improve the reductive properties of triazophos and eliminate interferences of other pesticides. In addition, the AuNPs can strikingly amplify the electrochemical response of triazophos and improve the sensitivity to triazophos. Finally, the electrochemical sensor was successfully applied to determination of triazophos in vegetable samples with satisfactory results.

Adsorption and degradation of triazophos, chlorpyrifos and their main hydrolytic metabolites in paddy soil from Chaohu Lake, China

Triazophos and chlorpyrifos are organophosphorus pesticides (OPs), and their primary hydrolytic metabolites are 1-phenyl-3-hydroxy-1,2,4-triazole (BZC) and 3,5,6-trichloro-2-pyridinol (TCP). In this study, the adsorption and degradation of triazophos, chlorpyrifos, BZC and TCP were investigated in paddy soil from Chaohu Lake, China. Adsorption tests demonstrated that the adsorption of these compounds to soils could be described by the Freundlich equation. Moreover, chlorpyrifos displayed the highest affinity for adsorption, followed by triazophos, BZC and TCP. Degradation of these compounds in non-sterile soil followed first-order exponential decay kinetics, and the half-life (t(1/2)) of these contaminants ranged from 8.40 to 44.34 d. Sterilization of soil decreased the degradation rate, indicating that microorganisms played a significant role in the degradation of these compounds. The values of t(1/2) and K(oc) were fitted to obtain models that could predict the leaching potential of the contaminants from soil. Compared to their parent compounds, BZC and TCP showed high potential for leaching into groundwater. The inoculation of OPs-degrading bacterium (Diaphorobacter sp. GS-1) removed 95.38%, 100% and 100% of triazophos, chlorpyrifos and BZC in paddy soil after 21 d, respectively. The pollution risk of triazophos, chlorpyrifos and BZC could be greatly decreased by inoculating soil with Diaphorobacter sp. GS-1, which decreases the t(1/2) of the contaminants.

Identification of the biochemical degradation pathway of triazophos and its intermediate in Diaphorobacter sp. TPD-1

Triazophos is one of the most widely used organophosphorus insecticides usually detectable in the environment. A bacterial strain, Diaphorobacter sp. TPD-1, capable of using triazophos and its intermediate, 1-phenyl-3-hydroxy-1,2,4-triazole (PHT), as its sole carbon sources for growth was isolated from a triazophos-contaminated soil in China. This strain could completely degrade 50 mg l(-1) triazophos and PHT to non-detectable level in 24 and 56 h, respectively. During PHT degradation, three metabolites were detected and identified based on tandem mass spectrometry (MS/MS) analysis. Using this information, a biochemical degradation pathway of triazophos by Diaphorobacter sp. TPD-1 was proposed. The first step involved in the degradation of triazophos is the hydrolysis of the P-O ester bond of triazophos to form PHT and o,o-diethyl phosphorothioic acid, then the triazol ring of PHT is subsequently cleaved to form (E)-1-formyl-2-phenyldiazene. Subsequently, (E)-1-formyl-2-phenyldiazene is transformed to 2-phenylhydrazinecarboxylic acid by adding one molecular of H(2)O. Finally, the carboxyl group of 2-phenylhydrazinecarboxylic acid is decarboxylated to form phenylhydrazine.

Photocatalytic degradation of triazophos in aqueous titanium dioxide suspension: identification of intermediates and degradation pathways

The photocatalytic degradation of triazophos in aqueous TiO2 suspension has been studied in a photoreactor operating with simulated solar radiation. The decrease in triazophos concentration followed first-order kinetics with a half-life of 4.76+/-0.42 h at a TiO2 suspension concentration of 10 mg/L. Seventeen degradation products were identified using HPLC-UV, HPLC/MS/MS, GC/MS/MS and IC, and by comparing retention times and spectra with commercially available authentic standards. On the basis of the observed transformation products, two routes were proposed, one based on the initial oxidative cleavage of PS bond to PO bond, and the other on initial cleavage of the ester P-O bonds. Photocatalysis holds promise for the solar treatment of pesticide-contaminated waters.

Isolation of a triazophos-degrading strain Klebsiella sp. E6 effectively utilizing triazophos as sole nitrogen source

A triazophos-degrading strain, Klebsiella sp. E6, was isolated by enrichment technology from soil that had been exposed long-term to triazophos. The strain grew well at pH 7.0-8.0 with a broad temperature profile ranging from 32 to 37 degrees C. It could keep good growth on methanol as carbon source and TAP as additional carbon source or nitrogen source. The experiment on the degradation activities of strain E6 showed that it utilized TAP more effectively when TAP was supplied as the sole nitrogen source, as opposed to additional carbon source. The intermediates of triazophos metabolism indicated that degradation occurred through a hydrolysis mechanism, one of the products of which, 1-phenyl-3-hydroxy-1,2,4-triazole, was also mineralized by strain E6.