Abstract View
Atmospheric Reactivity of Brake Wear Particulate Matter: Implications for Predicting and Improving Air Quality
LAURA MATCHETT, Kristyna Stix, Maya Abou-Ghanem, Sarah Styler, University of Alberta
Abstract Number: 578
Working Group: Aerosol Chemistry
Abstract
Atmospheric particulate matter (PM) is a concern for human health, visibility, and climate. In urban environments, vehicular traffic emits large quantities of PM through either exhaust (engine combustion) or non-exhaust (brake, tire, and road abrasion) processes. Due to regulations and technological improvements surrounding exhaust emissions, non-exhaust emissions are becoming the dominant contributor to traffic PM. One of the largest sources of non-exhaust emissions is brake wear. Although studies have examined its emission, size, chemical composition, and toxicity, virtually nothing is known regarding its atmospheric reactivity. One measure of reactivity is the extent to which brake wear interacts with pollutant gases, which could alter both the concentration of the gas and the properties (e.g. toxicity) of the PM. In this study, we used a coated-wall flow tube apparatus to determine uptake coefficients for ozone, an important urban pollutant, at the surface of three types of brake wear (ceramic, semi-metallic, and organic) under both dark and light conditions. We find that all types are very reactive with ozone in the dark and that their reactivity increases in the presence of light, which may reflect photocatalytic contributions from metal oxides and light-absorbing organic species found in brake wear. The uptake coefficients for the three types of brake wear differ, which may reflect the significant differences seen in their composition. To elucidate which components of brake wear may be contributing to the observed reactivity, we also investigated the uptake of ozone by some of the main components in our samples: phenolic resin, graphite, iron powder, and iron oxide. Although the uptake coefficients for these brake wear types differ, they are within one order of magnitude; this has the potential to simplify the implementation of this chemistry into atmospheric models, leading to a better understanding of urban air quality.