Characterization of Ultrafine Particle Formation from Non-Tailpipe Vehicular Emissions

MADELINE COOKE, Adam Thomas, Michelia Dam, Véronique Perraud, Lisa Wingen, Barbara Finlayson-Pitts, James Smith, University of California, Irvine

     Abstract Number: 373
     Working Group: Aerosol Chemistry

Abstract
Ultrafine particles (UFP), particulate matter less than 100 nm in diameter, impact atmospheric chemistry, degrade air quality, and negatively impact human health. Traffic emissions are a main source of particulate matter in urban environments, comprised of two categories: exhaust emissions generated from combustion, and non-tailpipe vehicular emissions generated primarily from brake and tire wear. With the national trend toward replacing combustion vehicles with electric vehicles, non-tailpipe sources are becoming increasingly important. In order to assess how this will impact air quality, it is important to fully characterize these emissions. While research in this area has historically focused on particulate matter in the coarse mode, several recent studies have demonstrated that emissions from brake and tire wear also contain a large fraction of particles in the UFP mode. Number concentrations and elemental chemical composition have been reported, but the physical and chemical (physicochemical) properties of these UFP are not well known. Herein, we investigate the physicochemical properties of UFP from non-tailpipe vehicular emissions and explore how the properties change based on the braking conditions (e.g., temperature, braking torque, friction) and environmental conditions (e.g., exposure to atmospheric oxidants or UV-photolysis). Our results can be applied to better predict how non-tailpipe emissions will impact urban air quality and climate, and provide data useful for mitigating the effects of non-tailpipe emissions moving forward.