Degradation of\nIsopyrazam in Soil: Kinetics, Microbial\nMechanism, and Ecotoxicity of the Transformation Product

The degradation of isopyrazam in soils was investigated\nthrough\nkinetics, microbial contributions, and transformation products (TPs).\nThen the acute toxicity of isopyrazam and its TP to Chlorella pyrenoidosa was explored. The half-lives\nof isopyrazam in cinnamon soil, red soil, and black soil were 82.2,\n141.7, and 120.3 days, respectively. A strain (<i>Bacillus</i> sp. A01) isolated from cinnamon soil could degrade 72.9% of isopyrazam\nat 10 mg/L after 6 days in a Luria–Bertani medium. Six TPs\nwere observed with <i>Bacillus</i> sp. A01, and three of\nthem were found in soil as well. Through the inhibition of cytochrome\nP450 enzymes, the production of oxidized isopyrazam was blocked. Microbial\nmediated hydroxylation, epoxidation, and dehydration were the main\ndegradation pathways of isopyrazam. The acute toxicity results showed\nthat the EC<sub>50</sub> of 3-(difluoromethyl)-<i>N</i>-(9-(2-hydroxypropan-2-yl)-1,2,3,4-tetrahydro-1,4-methanonaphthalen-6-yl)-1-methyl-1<i>H</i>-pyrazole-4-carboxamide to Chlorella pyrenoidosa was 40 times higher than that of the parent. This work provides\nnew insights for understanding the degradation behavior of isopyrazam\nin soil.