Collaborative Research: CAS: Sunlight- and Oxidant-Induced Transformation of Tire-Derived Contaminants on Roadway-Associated Surfaces

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With support from the Environmental Chemical Sciences Program of the NSF Division of Chemistry, Ning Dai, Prathima Nalam, and Ravi Ranade at the University at Buffalo-the State University of New York and Michael Dodd and Edward Kolodziej at the University of Washington will study the transformation of tire rubber-derived contaminants on roadway surfaces that are exposed to sunlight and airborne oxidants such as oxygen, ozone, and hydroxyl radical. Particles generated from the wear of tires during transportation on roads contribute substantially to water, soil, and air pollution. The complicated mixture of rubber compounds and proprietary additives arising from such particles, as well as their transformation products, can have severe adverse impacts on ecosystems. Both sunlight and ozone are known reactants in water, but their roles in transforming contaminants on roadway-associated surfaces such as tire rubber, concrete, and asphalt pavements are largely unknown. This project will conduct research to address these critical knowledge gaps. In addition, this project will include a series of synergistic educational activities comprising K-12 teacher and community college outreach, engagement with citizen science groups, and project-based research experiences for undergraduate students. This project will evaluate the independent and combined effects of sunlight and airborne oxidants on the transformation of tire-derived organic contaminants on roadway-associated surfaces. The transformation kinetics, mechanisms, and product compositions from surface reactions will be characterized and compared against expectations for bulk gas and aqueous phase reactions. By using a suite of carefully selected, environmentally relevant contaminants and their structural analogues, the project will yield new insights on interfacial photochemical and redox processes occurring on roadway surfaces, which can enable modeling of the environmental behaviors and potential ecosystem and human health risks of these and many other tire-derived contaminants. Structure-activity relationships determined from this project can be used to inform the selection and/or design of new tire rubber components that are safer to the environment. The findings from this project have the potential to contribute to environmentally safer and more sustainable roadways while informing the development of sustainable, tire rubbers with reduced ecological impact.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.