CAS: Environmental Degradation Pathways for Some Emerging Contaminants

University Of California-Irvine, Irvine CA

Investigators

Abstract

With this award, the Environmental Chemical Sciences Program of the NSF Division of Chemistry supports research by Professor Barbara Finlayson-Pitts and her group to address the environmental fate of emerging contaminants (EC), which are chemicals that are not commonly monitored but may become widely distributed in the environment. They can have adverse effects on human health and ecological systems. This class of compounds includes some pharmaceuticals, pesticides and munitions. Once in the environment, these compounds can undergo reactions that either make them less, or in some cases, more toxic. Thus, understanding their fates once released is important for understanding the health and environmental risks as well as for guiding the future development of less harmful substitutes. The research in the Finlayson-Pitts group is directed at understanding the fundamental processes that occur when certain classes of EC are exposed to sunlight or oxidants found in the atmosphere. This provides information on how fast they will react in air and the nature of the products formed that can be used to guide toxicology studies. The project provides research opportunities for a postdoctoral student as well as several undergraduate students. The PI also engages in a variety of outreach and training activities through the AirUCI Institute which she leads. To accomplish these goals, a combination of experimental approaches is used to study compounds that contain amine, nitro and in some cases, alkene groups. Thin films of the EC on infrared transmitting crystals are irradiated, and the loss of the EC and formation of products are followed in real time. Alternatively, the thin films are monitored during exposure to gas phase ozone. The mixtures of unreacted EC and its reaction products are extracted into solution and analyzed by a variety of separation and mass spectrometry techniques. Kinetics modeling is applied to determine the contributions of reaction and diffusion that occur in the gas-solid reactions. Model compounds for the EC are also exposed to ozone, a strong oxidant, in the gas phase. This provide insights into the factors that control the oxidation and to find differences between similar reactions in the gas versus the condensed phase. These data provide a fundamental understanding of some of the degradation pathways that are likely to be important when these compounds are released into the environment. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.