Neonicotinoid insecticides represent 25% of current global insecticide use and have been widely detected in soil, surface water, and groundwater. Photolysis is an important transformation pathway for neonicotinoids and has been previously investigated in aquatic systems, but much less in known about photolysis on surfaces. In this work, photolysis of four neonicotinoids (imidacloprid, thiamethoxam, clothianidin and acetamiprid) was evaluated on four surfaces: glass, aluminum foil, paraffin wax, and leaves from strawberry plants. Experiments were performed with pure compounds dissolved in water and commercially available formulations applied to the surfaces. The degradation rates on paraffin wax and leaves were comparable, but were much lower than those on glass and aluminum foil, indicating that paraffin wax best simulates the reaction environment on leaves. Degradation of pure imidacloprid and pure clothianidin followed zero order kinetics on all surfaces, while pure thiamethoxam followed first order kinetics. In addition, the loss of commercial formulations was much faster than the pure compounds, implying that real products containing various active and inert ingredients can lead to a significant change in the photolysis process. Using 2-nitrobenzaldehyde as an actinometer allows determination of quantum yields, and product formation was evaluated using LC-MS/MS. These results suggest that the photolysis pathways on surfaces may be different that those in aqueous solutions.

Photolysis of neonicotinoid insecticides on model and real leaf surfaces

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.