Photochemical fate and advanced oxidation of Pyrimethanil in waters and wastewater

Commonly used fungicide pyrimethanil (PYR) has been detected in various aquatic environments, presenting persistence, adverse effects on ecology and resistance to conventional degrading methods1,2. In this study, the abiotic phototransformation of PYR was investigated under simulated solar irradiation (SSI). The results indicated that photolysis was the principal degradation process, following pseudo – first order kinetics in the following order: ultra-pure < sea < lake < river water. The impact of prevalent water components such as humic acid, Fe3+, NO3-, and Cl- was examined. Furthermore, sulfate radical-based advanced oxidation processes (SR-AOPs) activated by SSI were explored for its removal from both ultra-pure water and wastewater. SSI/persulfate (PS) exhibited the best degradation efficiency, achieving 100% PYR removal in 240 min, compared to PMS and H2O2. Wastewater experiments significantly affected the degradation efficiency, leading to a 55% decrease in first-order reaction rate constant. Scavenging studies assessed the role of reactive species revealing •OH as the dominant contributor concerning SSI/PS process. Major phototransformation routes include C–N bond cleavage, hydroxylation, and oxidative ring opening as indicated by liquid chromatography-high-resolution mass spectrometry (LC-HRMS). Potential environmental implications of photoproducts were evaluated using in vitro (Microtox assay) and in silico (ECOSAR) ecotoxicity tools.