Atmospheric Fates of Neonicotinoid Insecticides

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This award is funded by the Environmental Chemical Sciences (ECS) Program in the Division of Chemistry. Professor Barbara Finlayson-Pitts and her group at the University of California-Irvine (UCI) study the environmental fate of neonicotinoid pesticides. There has been a significant, recent, worldwide decline in bees, which play a major role in pollination. Neonicotinoid pesticides have been implicated in this decline, along with other factors such as parasites and pathogens, loss of habitat and diversity of pollinators. Neonicotinoid pesticides have low toxicity to mammals. However, in the atmosphere they may undergo transformations to form new products that are more toxic than the parent compounds. The goals of this project are to elucidate the atmospheric reactions of neonicotinoids, the rate at which they are changed into other molecules in the environment, and the nature of the resultant molecules. The results of this research will contribute to a molecular level understanding of the atmospheric lifetimes and fates of neonicotinoid pesticides in the environment. The data collected enable scientists to establish the risk assessments for these compounds. Training in current techniques for studying heterogenous chemistry on surfaces is provided to a diverse group of students and postdoctoral fellows. The goal of this research is to provide a molecular level understanding of the photochemistry of surface-bound neonicotinoid insecticides (NNs) and their reactions with trace atmospheric gaseous oxidants. NNs have found increasing use since their first introduction about 25 years ago, largely as seed coatings and soil treatments. Their reactions once in the atmosphere are not well known. This project studies the photochemistry and atmospheric reactions of seven commonly used neonicotinoids which are nitroguanidines (imidacloprid, thiamethoxam, clothianidin and dinotefuran), cyanamidines (thiacloprid and acetamiprid) or nitromethylenes (nitenpyram). The quantum yields for photolysis of the compounds that absorb light at wavelengths relevant to the atmosphere are measured. Also, both the gas phase and solid state products are determined using a variety of techniques. These techniques include attenuated total reflectance and transmission Fourier transform infrared spectrometry and several mass spectrometry techniques. The identity and yields of the products and the kinetics of oxidation by ozone, the hydroxyl radical and the nitrate radical are measured. This is used for a quantitative assessment of the atmospheric lifetimes and fates of neonicotinoids in air.Professor Finlayson-Pitts' is the Co-Director of AirUCI, a collaborative group of faculty at UCI that sponsors a number of educational initiatives, including student research retreats, training in effective communication and discussions of career options. Collaborations and hosting international visitors provides breadth of experience and networking opportunities to group members.