Jim Smith, Professor
Department of Chemistry
Univeristy of California, Irvine

Beyond the Tailpipe: Trace Gas and Aerosol Emissions from Automotive Braking

Abstract: As the world transitions away from internal combustion engines, non-tailpipe sources (brake-wear, tire-wear, road dust resuspension) already rival tailpipes as a primary source of PM2.5 road transport emissions yet very little is known about the nature of these emissions. This talk will focus on measurements of the composition and physical properties of gases and particles generated from automotive braking. Experiments were performed using a unique facility designed to replicate temperatures and torques that are applied to brakes in actual use for passenger vehicles. We have observed that sub-micron particles from light braking exhibit dynamic oxidation states, with oxidation state increasing as rotor temperature increases. Ultrafine particles are generated in substantial quantities during heavier braking and are less oxidized, with CHO and CHON species dominating the organic fraction. We also found substantial HONO formation associated with braking. Surprisingly, we found that brake wear particles can be highly charged. This suggests that future mitigation efforts aiming to exploit aerosol electrical properties could be highly effective for controlling brake wear emissions.  

Bio: Jim Smith is a professor of Chemistry at the University of California, Irvine. His research interests focus on understanding and quantifying the mechanisms of atmospheric nanoparticle formation and growth through laboratory and field measurements. He is the developer of the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS), one of a few instruments capable of size-resolving and measuring the molecular composition of particles with diameters as small as 4 nm. Prof. Smith received his B.S. in physics at Harvey Mudd College and his Ph.D. in Environmental Science and Engineering at the California Institute of Technology.