Ma Chang, Liu Xingang, Wu Xiaohu, Dong Fengshou, Xu Jun, Zheng Yongquan
State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
J Hazard Mater. 2021 Feb 5;403:124033. doi: 10.1016/j.jhazmat.2020.124033. Epub 2020 Sep 19.
Hydrolysis and photolysis are important degradation pathways of pesticides while their degradation in soil is a principal metabolic pathway. These processes might generate toxic chemicals and pose threats to the environment. As a member of the controversial neonicotinoid pesticides, the environmental fate and toxicity of imidaclothiz and its potential metabolites have remained ambiguous. Laboratory experiments were conducted to study the degradation kinetics, mechanisms and toxicity of imidaclothiz in aqueous solutions (pH = 4, 7, 9 buffer solutions and ultra-pure water) and soil (black soil, red soil and fluvo-aquic soil) under different conditions (25 ℃ and 50 ℃). The results showed that imidaclothiz was fairly stable in water and soil under natural conditions. Based on the mass accuracy of the parent chemical and conserved fragment ions, ten candidate degradation products were filtered out using UHPLC-QTOF-MS and the UNIFI system. Then, two of the candidates were synthesized, analysed, and compared with standards to confirm. The microscopic mechanisms of three degradation reactions (imidaclothiz degraded to M216, M216 degraded to M217 and M216 degraded to M198) were elucidated using theoretical calculations. The toxicity data from experiments and the ECOSAR prediction showed that imidaclothiz had low toxicity to Daphnia magna and Danio rerio and had high toxicity to Apis mellifera, with 50% of the degradation products in this study exhibiting higher toxicities to aquatic organisms than the parent chemical.
水解和光解是农药重要的降解途径，而它们在土壤中的降解是主要的代谢途径。这些过程可能会产生有毒化学物质并对环境构成威胁。作为有争议的新烟碱类农药的一员，咪啶噻虫啉及其潜在代谢物的环境归宿和毒性仍不明确。开展了实验室实验，以研究咪啶噻虫啉在不同条件（25℃和50℃）下在水溶液（pH = 4、7、9缓冲溶液和超纯水）和土壤（黑土、红土和潮土）中的降解动力学、机制和毒性。结果表明，在自然条件下，咪啶噻虫啉在水和土壤中相当稳定。基于母体化合物和保守碎片离子的质量精度，使用超高效液相色谱-四极杆飞行时间质谱仪（UHPLC-QTOF-MS）和UNIFI系统筛选出10种候选降解产物。然后，合成了其中两种候选产物，进行分析并与标准品进行比较以确认。利用理论计算阐明了三个降解反应（咪啶噻虫啉降解为M216、M216降解为M217以及M216降解为M198）的微观机制。实验毒性数据和ECOSAR预测表明，咪啶噻虫啉对大型溞和斑马鱼毒性较低，对意大利蜜蜂毒性较高，本研究中50%的降解产物对水生生物的毒性高于母体化合物。
