Pesticide Transformation by Nitrogen Oxides on Leaf Surfaces

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In this project funded by the Environmental Chemical Sciences Program of the Division of Chemistry, Professors Ning Dai and Luis Velarde at the University at Buffalo are investigating the contribution of atmospheric nitrogen oxides to the changes in pesticides which reside on leaf surfaces. Due to the widespread use of pesticides in agricultural and urban environments and their inherent toxicity, it is critical to develop capabilities to accurately predict the changes that occur in these molecules on exposure to the environment. This research project addresses a pesticide transformation pathway that is currently not considered in the predictive models. The research is integrated with synergistic educational activities, including training of graduate students, research experiences for undergraduate students, incorporation of research into the Environmental Engineering curriculum at the University at Buffalo, and public science outreach for high school teachers and underrepresented high school students in the Greater Buffalo region.This project identifies pesticide functional groups that are susceptible to nitrogen oxide reactions in water and organic solvents. The kinetics and products of nitrogen oxide-induced pesticide transformation are then determined on simulated and authentic leaf surfaces. The effects of environmental factors, including sunlight, pesticide formula, and the structure of leaf cuticle wax, on the reactions are also characterized. Lastly, vibrational sum frequency generation (VSFG) spectroscopy is employed to characterize the molecular orientation and tethering of surface-bound pesticides and their transformation products on model leaf surfaces. This characterizational technique is used to correlate the pesticide-leaf physical interaction with nitrogen oxide-pesticide reactions.