Study of intense pulsed light as a new remediation process for pesticides in water using mass spectrometry and ecotoxicological approaches

• Pulsed-light proved effective to photodegrade 20 pesticides in water. • 74 photoproducts were observed and 47 chemical structures proposed. • Fluence and voltage affect photodegradation of pesticides. • Acute toxicity decreased by 7.25-fold for a cocktail of 18 pesticides. Pulsed light (PL) technology was investigated as a pesticide removal process. The degradation of 20 pesticides in water was monitored by mass spectrometry and revealed 74 photoproducts. Structure hypotheses were proposed for 47 photoproducts according to their fragmentation, isotopic pattern, and literature data. This work enabled the development of a LC-MS method for the relative quantification of photoproducts and for the absolute quantification of their parent pesticides. This analytical method was then applied in optimizing the PL parameters. It was demonstrated that increasing voltage and fluence leads to more efficient pesticide degradation, with concentration reduction of 99 % for 14 pesticides. The compound sensitivity seems to be family dependent. Moreover, PL succeeded in degrading the photoproducts themselves. Acute toxicity tests were performed on the bacteria A liivibrio fischeri . A significant reduction in toxicity was observed for 10 out of 18 individual pesticides, while no increase was observed for the remaining seven. When applied to a cocktail solution, the toxicity decreased by 7.25-fold between the untreated and the most PL treated solution. This work demonstrates that PL is a promising process for removing pesticides from contaminated water. Further studies are needed to demonstrate the safety of treated wastewater on various trophic links.