Oxidation of the Neonicotinoid Acetamiprid on Particles and Solids by OH Radicals: Top-Down versus Bottom-Up

WEIHONG WANG, Xinke Wang, Lisa Wingen, Véronique Perraud, Barbara Finlayson-Pitts, University of California Irvine

     Abstract Number: 114
     Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts

Abstract
Emerging contaminants (EC) are widely distributed on particles and other environment surfaces. They can be oxidized by gas phase species or by oxidants generated by underlying substrates. This may result in more toxic products, posing risks to both humans and the environment. Neonicotinoid (NN) pesticides which have been widely used since 1991 fall under the umbrella of EC. They have been found on airborne particles and other surfaces in the environment, resulting in widespread dispersion and the potential for human exposure. In addition, they have been associated with bee colony collapse. Oxidation of the NN pesticide acetamiprid (ACM) by the OH radical was studied where the ACM was on particles or on solid substrates. Hydroxyl radicals were generated either in the gas phase where the radicals attacked the solid ACM from the top down, or from an underlying TiO₂ or NaNO₂ substrate that generates OH on photolysis and attacks the ACM from the bottom up. The major products, mechanisms and kinetics of OH oxidation of ACM under both circumstances will be reported and compared to oxidation in the aqueous phase. The results of this study highlight the different potential oxidation processes for EC and provide key data for assessing their environmental fates and toxicology.