Photodegradation is one of the primary abiotic mechanisms by which pesticides degrade. In the Central Valley of California, large quantities of herbicides are used every year to control unwanted plant growth and can ultimately affect agroecosystems, particularly through the water supply. Phenylurea herbicides such as diuron, and linuron are among those most widely used and also among the greatest concern for ground and surface water contamination. Here, we compute the most probable photodegradation pathways and products for a series of phenylurea herbicides through quantum chemical studies of the electronically excited states and their initial forces. The calculations were done using standard Density Functional methods as implemented in Q-Chem, coupled with a more recently developed algorithm for exploring potential energy surfaces. We found many similarities between these molecules but also some very interesting differences relating to their functional groups. Ultimately, the goal is to efficiently and accurately predict photodegradation products for a selected class of molecules, which can potentially lead to developing safer but effective alternatives for widely used pesticides.

Mechanism of photodegradation in phenylurea herbicides

ACS Fall 2020 Virtual Meeting

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