Degradation of enestroburin in the water-sediment system: kinetics, transformation products identification and toxicity assessment to aquatic organisms

Pesticides inevitably enter the water environment in the process of use. However, the degradation and its transformation products (TPs) of enestroburin in water-sediment systems are not yet known. This study systematically investigated the degradation behaviour of enestroburin through indoor simulation experiments. The study demonstrated that the different organic content of sediments and oxygen conditions had a little effect on the degradation. The study also analysed transformation products by UPLC-QTOF-MS and MetabolitePilot software. A total of 3 TPs of enestroburin were identified, and one product (M-381) was confirmed and quantified. Based on these transformation products, the pathways of enestroburin were supposed, namely hydrolysis of chlorobenzene, hydrolysis of ester group and electrophilic substitution of benzene ring. Finally, ECOSAR software was utilised to predict the potential toxicity of the proposed TPs towards fish, daphnids, and green algae. The toxicity of TPs to aquatic organisms is lower than the parent compound, but they are still toxic. The study results provide data to support the safe use of enestroburin and provide a reference for the degradation and transformation of other strobilurin fungicides.