DFT insights into the degradation mechanism of carbendazim by hydroxyl radicals in aqueous solution

Highly sensitive electrochemical quantification of carbendazim via synergistic enhancement of ring-opening metathesis polymerization and polyethyleneimine modified graphene oxide

A novel aptamer-based sensor was developed using the signal amplification strategy of ring-opening metathesis polymerization (ROMP) and polyethyleneimine modified graphene oxide to achieve trace detection of carbendazim (CBZ). The dual identification of aptamer and antibody was used to avoid false positive results and improve the selectivity. Polyethyleneimine modified graphene oxide (GO-PEI), as a substrate material with excellent conductivity, was modified on the surface of a glassy carbon electrode (GCE) to increase the grafting amount of aptamer on the electrode surface. Moreover, a large number of cyclopentenyl ferrocene (CFc) was aggregated to form long polymer chains through ring-opening metathesis polymerization (ROMP), so as to significantly improve the detection sensitivity of the biosensor. The linear range of this sensor was 1 pg/mL-100 ng/mL with a detection limit as low as 7.80 fg/mL. The sensor exhibited excellent reproducibility and stability, and also achieved satisfactory results in actual sample detection. The design principle of such a sensor could provide innovative ideas for sensors in the detection of other types of targets.

Unveiling the Aftermath: Exploring Residue Profiles of Insecticides, Herbicides, and Fungicides in Rice Straw, Soils, and Air Post-Mixed Pesticide-Contaminated Biomass Burning

This study delved into the impact of open biomass burning on the distribution of pesticide and polycyclic aromatic hydrocarbon (PAH) residues across soil, rice straw, total suspended particulates (TSP), particulate matter with aerodynamic diameter ≤ 10 µm (PM10), and aerosols. A combination of herbicides atrazine (ATZ) and diuron (DIU), fungicide carbendazim (CBD), and insecticide chlorpyriphos (CPF) was applied to biomass before burning. Post-burning, the primary soil pesticide shifted from propyzamide (67.6%) to chlorpyriphos (94.8%). Raw straw biomass retained residues from all pesticide groups, with chlorpyriphos notably dominating (79.7%). Ash residue analysis unveiled significant alterations, with elevated concentrations of chlorpyriphos and terbuthylazine, alongside the emergence of atrazine-desethyl and triadimenol. Pre-burning TSP analysis identified 15 pesticides, with linuron as the primary compound (51.8%). Post-burning, all 21 pesticides were detected, showing significant increases in metobromuron, atrazine-desethyl, and cyanazine concentrations. PM10 composition mirrored TSP but exhibited additional compounds and heightened concentrations, particularly for atrazine, linuron, and cyanazine. Aerosol analysis post-burning indicated a substantial 39.2-fold increase in atrazine concentration, accompanied by the presence of sebuthylazine, formothion, and propyzamide. Carcinogenic PAHs exhibited noteworthy post-burning increases, contributing around 90.1 and 86.9% of all detected PAHs in TSP and PM10, respectively. These insights advance understanding of pesticide dynamics in burning processes, crucial for implementing sustainable agricultural practices and safeguarding environmental and human health.

Carbendazim residue in plant-based foods in China: Consecutive surveys from 2011 to 2020

Carbendazim, a widely used fungicide in China, has been found to have reproductive toxicity and mutagenic effects. However, information on the spatial-temporal variations of carbendazim residues in food in China is limited. Here, we investigated the presence of carbendazim in China's plant-based foods from 2011 to 2020, evaluated the spatial-temporal characteristics, and assessed the associated exposure risks in the Chinese diet. The results revealed a high detection frequency of carbendazim in fruits (26.4%) and high concentrations in vegetables (∼110 mg kg-1), indicating widespread misuse of the fungicide. The acute risks of consuming certain vegetables and cereals exceeded the recommended limits by up to 12 and 5 times, respectively. Although there has been a decline in carbendazim residue levels in food since the implementation of the Chinese government's action plan for zero growth of pesticide use in 2015, some provinces still exhibited high levels of carbendazim in multiple food categories, which were positively correlated with annual pesticide application. We highlight that carbendazim contamination reflects the broader issue of pesticide use in China. It emphasizes the need for committed and targeted national policies to reduce carbendazim residues in food and suggests that such measures could also regulate the use of other pesticides, given that pesticide abuse in China is not limited to specific types. We call for the re-evaluation of maximum residue limits of carbendazim, particularly in highly consumed foods such as cereals.

Insight into functional mechanisms of percarbamide and nitrification inhibitors in degrading fungicide residues and shaping microbial communities in soil-plant systems

Fungicides and nitrogen (N) fertilizers are essential to maintain plant yield in current intensive agriculture. Percarbamide is a novel type of N fertilizer with strong oxidizing property, and the nitrification inhibitor is widely used in agricultural production. It may be feasible to apply percarbamide and nitrification inhibitor as N management to promote fungicide dissipations in soil-plant system. This study quantified the effects of percarbamide and nitrification inhibitor dicyandiamide (DCD) and 3, 4-dimethylpyrazole phosphate (DMPP) on carbendazim residues, and microbial communities of soil-plant systems, and relationships among carbendazim residues, soil and endophytic microbial communities and plant yields were also comprehensively quantified. Compared with the control, the percarbamide significantly reduced soil carbendazim residues by 29.4% but enhanced the lettuce yield by 28.0%. Soil carbendazim residues were significantly and negatively correlated with the soil total N and NO3--N contents. Soil microbial community structures and co-occurrence networks were more sensitive to N management than their endophytic counterparts. In comparison to the percarbamide alone, the DCD significantly increased the nodes of soil fungal community co-occurrence network which were positively correlated with the plant yield. The DCD outweighed DMPP in increasing the lettuce yield and soil fungal community stability and reshaping soil bacterial community structure. Our study suggested that soil microbial communities were more sensitive to percarbamide and nitrification inhibitor applications than their endophytic counterparts under fungicide pressure and that the DCD outweighed DMPP in reshaping microbial communities. The integrated applications of percarbamide and nitrification inhibitors were promising soil N management strategies to promote fungicide removal and stimulate microbial community in the soil-plant systems.

Plasmonic photocatalytic degradation of tebuconazole and 2,4-dichlorophenoxyacetic acid by Ag nanoparticles-decorated TiO2 tracked by SERS analysis

Chemical oxidation technologies have been notably used for the mineralization of organic pollutants from aqueous effluents, been especially relevant for the degradation of pesticides. In this context, both tebuconazole (TEB) and 2,4-dichlorophenoxyacetic acid (2,4-D) pesticides were photodegraded by a combined catalyst of TiO2 and silver nanoparticles irradiated by UV-A light (λmax = 368 nm), and the experiments were tracked by surface-enhanced Raman scattering (SERS) spectroscopy. For 2,4-D, the degradation of about 70% was observed after almost 200 min, while for TEB, a decrease of 80% of the initial concentration was observed after approximately 100 min. The SERS monitoring allowed the proposal of some by-products, such as oxidized aliphatic chain and triazole from TEB besides glycolic, glyoxylic and dihydroxyacetic acids from 2,4-D. Their toxicities were predicted through ECOSAR software, verifying that most of them were not harmful to populations of fish, Daphnia and green algae. Thus, the performed oxidative process was efficient in the photodecomposition of TEB and 2,4-D pesticides, inclusive in terms of the decreasing of the toxicity of contaminated effluents.

Xenon-lamp simulated sunlight-induced photolysis of pyriclobenzuron in water: Kinetics, degradation pathways, and identification of photolysis products

Pyriclobenzuron 1(PBU) is a novel molluscicide developed to control Pomacea canaliculate, and little information on its environmental fate has been published. In this study, the photolysis of PBU in an aqueous environment was simulated using a xenon lamp. Results showed that the photolysis of PBU in water followed first-order kinetics, exhibiting a t0.5 of 95.1 h and 83.6 h in Milli-Q water and river water, respectively. Two main photolysis products 2(PPs) were detected by HPLC-UV and identified by UPLC-Q/TOF MS, which were formed via the hydroxylation and photocatalytic hydro-dehalogenation of PBU, respectively. The initial relative abundance of photolysis product 1 3(PP-1) in Milli-Q water was 1.55 times higher than that in river water. PP-1 was detected at 26.5 % and 76.8 % of the maximum relative abundance in the river water and Milli-Q water after 720 h, respectively. Photolysis product 2 4(PP-2) was stable in water because of its weak hydrophilicity. The PP-2 detected after 720 h in Milli-Q water and river water was 93.7 % and 93.5 % of the maximum relative abundance, respectively. Finally, ECOSAR software was used to evaluate the acute aquatic toxicity of PBU and its PPs, revealing that the PPs had lower toxicity levels to non-target aquatic organisms.

Photodegradation fate of different dissociation species of antidepressant paroxetine and the effects of metal ion Mg2+: Theoretical basis for direct and indirect photolysis

Paroxetine (abbreviated as PXT) has been widely used as one of the standard antidepressants for the treatment of depression. PXT has been detected in the aqueous environment. However, the photodegradation mechanism of PXT remains unclear. The present study aimed to use density functional theory and time-dependent density functional theory to study the photodegradation process of two dissociated forms of PXT in water. The main mechanisms include direct and indirect photodegradation via reaction with ·OH and ¹O₂ and photodegradation mediated by the metal ion Mg²⁺. Based on the calculations, PXT and PXT-Mg²⁺ complexes in water are photodegraded mainly indirectly and directly. It was found that PXT and PXT-Mg²⁺ complexes were photodegraded by H-abstraction, OH-addition and F-substitution. The main reaction of PXT indirect photolysis is OH-addition reaction, while the main reaction of PXT⁰-Mg²⁺ complex is H-abstraction. All the reaction pathways of H-abstraction, OH-addition and F-substitution are exothermic. PXT⁰ reacts more readily with ·OH or ¹O₂ in water than PXT⁺. However, the higher activation energy of PXT with ¹O₂ indicates that the ¹O₂ reaction plays a minor role in the photodegradation pathway. The direct photolysis process of PXT includes ether bond cleavage, defluorination, and dioxolane ring-opening reaction. In the PXT-Mg²⁺ complex, the direct photolysis process occurs via a dioxolane ring opening. Additionally, Mg²⁺ in water has a dual effect on the direct and indirect photolysis of PXT. In other words, Mg²⁺ can inhibit or promote their photolytic reactions. Overall, PXT in natural water mainly undergo direct and indirect photolysis reactions with ·OH. The main products include direct photodegradation products, hydroxyl addition products and F-substitution products. These findings provide critical information for predicting the environmental behavior and transformation of antidepressants.

Carbendazim: Ecological risks, toxicities, degradation pathways and potential risks to human health

Carbendazim is a highly effective benzimidazole fungicide and is widely used throughout the world. The effects of carbendazim contamination on the biology and environment should be paid more attention. We reviewed the published papers to evaluate the biological and environmental risks of carbendazim residues. The carbendazim has been frequently detected in the soil, water, air, and food samples and disrupted the soil and water ecosystem balances and functions. The carbendazim could induce embryonic, reproductive, developmental and hematological toxicities to different model animals. The carbendazim contamination can be remediated by photodegradation and chemical and microbial degradation. The carbendazim could enter into human body through food, drinking water and skin contact. Most of the existing studies were completed in the laboratory, and further studies should be conducted to reveal the effects of successive carbendazim applications in the field.

Near-Infrared Fluorescent Probe for H2S Detection: Will pH Affect the Intracellular Sensing?

Near-infrared (NIR) fluorescent probe has exhibited unique advantages for in vitro and in vivo detection of hydrogen sulfide (H₂S), an important endogenous gasotransmitter in redox homeostasis and multiple life processes. However, both the pH-dependent emission of NIR probes and H₂S conversions would normally affect the accurate detection in cellular environments in different acidic conditions. Herein, both experiments and theoretical calculations were carried out to examine the effect of pH on intracellular sensing of H₂S by the NIR probe. Selecting a NIR probe of R1 with dual-excited NIR responses to H₂S as the model, the pH-dependent R1 emission was confirmed by optical measurements, whose structural changes were further examined by mass spectrometry (MS). Significantly, the dynamic changes versus pH increase were employed for the online monitoring of ambient MS (AMS), observing important intermediate species without sample pretreatments. Thereby, intermediates and transition states were confirmed by theoretical calculations, which proposed the mechanism of nucleophilic substitution, followed by the hydrolysis process with increasing pH. As examined, R1 exhibited a relatively stable NIR emission at pH 4-8, while a dramatic change in signals occurred at higher-pH conditions. Therefore, R1 was demonstrated to be reliable for intracellular sensing of H₂S and had been confirmed by cell imaging. This work has initiated a comprehensive strategy for evaluating fluorescence (FL) probes, showing potential for the development of fluorescent probes.