Non-Tailpipe Emissions from Ambient and Laboratory Measurements: Commonalities in Environmentally Persistent Free Radicals, Reactive Oxygen Species and Oxidative Potential of Brake Wear, Tire Wear and Road Dust
SUKRITI KAPUR, Kasey Edwards, David Herman, Madeline Cooke, Adam Thomas, Tsuyoshi Ito, Hiroyuki Hagino, Junichi Hosoya, Tazuko Morikawa, Lisa Wingen, Véronique Perraud, Andrea De Vizcaya Ruiz, Michael Kleinman, James Smith, Barbara Finlayson-Pitts, Manabu Shiraiwa, University of California, Irvine
Abstract Number: 544
Working Group: Aerosol Processes and Properties in Changing Environments in the Anthropocene
Abstract
Non-tailpipe emissions, make up an important but understudied class of vehicular pollutants. Due to lack of regulations, emissions from non-tailpipe sources, primarily brakes, tires and resuspended dust are on the rise. As non-tailpipe emissions continue to rise, it becomes increasingly important to understand their health implications and oxidative potential. We studied environmentally persistent free radicals (EPFRs), reactive oxygen species (ROS), and oxidative potential (OP) of PM2.5 collected near freeways in Santa Ana (I-5) and Long Beach (I-710), comparing them to laboratory- generated brake wear particles (BWPs), road dust, and tire tread (fresh and used). Our results show a strong correlation among non-tailpipe markers in the field samples, highlighting contribution of NEE to PM2.5 near freeways. EPFRs in fresh tire tread were found to be comparable to ambient levels, and higher than in road dust. EFPRs from used tire tread showed highest value out of all samples (2.38 ± 0.73 pmol µg-1), likely due to photoaging of tire tread. BWPs and fresh tire tread formed hydroxyl radicals exclusively in aqueous phase, while ambient PM generate carbon-centered radicals and hydroxyl radicals. Three different brake wear PM10 with varying copper content (0.8-6.4%) showed that a higher copper content leads to higher ROS and oxidative potential with dithiothreitol (DTT) activity. These results have important implications for understanding health effects from vehicular non-tailpipe sources.