Toxicity Assays of Commercial Chlorpyrifos Under UV/H 2 O 2 and UVC Photolysis Treatments

This work evaluated the degradation efficiency of the most used commercial pesticide chlorpyrifos (CP) by UV/H 2 O 2 and UVC photolysis processes. Photodegradation was carried out with 200 μg L −1 of commercial CP for 30, 60, 90, 120, 240, 360, and 480 min. The samples were submitted to the liquid–liquid extraction technique and analyzed by HPLC–DAD. Bioassays were performed using two organisms, Daphnia magna and Aedes aegypti larvae, at all the degradation times. The degradation rate was 98% and 99% after 30 min of reaction for the UV/H 2 O 2 process and UVC photolysis, respectively. Moreover, during treatment, the main CP by-product, chlorpyrifos oxon (CPO), was identified among other unknown by-products. Acute toxicity with D. magna showed a decrease in the immobility at 480 min by the UV/H 2 O 2 process, while in UVC photolysis, 100% immobility was observed for up to 90 min of treatment, and the endpoint oscillated until the end of the process. Bioanalytical monitoring with A. aegypti showed no toxic effects on samples treated by the UV/H 2 O 2 process at 60, 90, 120, and 480 min of degradation. Despite the detection of CPO after UVC photolysis from 60 min onwards, no toxicity was verified, indicating that the by-products generated were not toxic to this organism. Therefore, even though high CP degradation rates were reached, for both processes, it was noted that bioassays and the ecotoxicological effect after degradation effluent are important to complement analytical tools. Graphical abstract