Environmental Fate and Ecological Risk of Microencapsulated Pesticide Suspensions in Water–Sediment Systems: A Case Study of Pyraclostrobin

Microencapsulated suspensions (MEs) are widely used in agriculture for their enhanced pesticide efficacy and minimal environmental impact. However, their release mechanisms and associated risks remain insufficiently explored. This study investigated the release, environmental fate, and risks of pyraclostrobin MEs using HPLC-Q-TOF-HRMS and UPLC-QqQ-MS/MS. Field experiments showed only 3.6% of pyraclostrobin was in free state in water, with most encapsulated in microcapsules that settled in sediment. Seventeen transformation products were identified, primarily accumulating in sediment. Predictions of persistence (P), bioaccumulation (B), mobility (M), and toxicity (T) revealed eight highly mobile and four highly toxic metabolites. Metabolites m/z 281 and m/z 339 showed significant chronic toxicity to daphnia, surpassing pyraclostrobin toxicity. Risk quotient analysis indicated that m/z 358 and m/z 611 posed a moderate risk to daphnia and mysid. The study highlights the importance of evaluating MEs, focusing on their release mechanisms and ecological risks to ensure safe pesticide use.