Atmospheric Chemistry Program Seminar
Grills and grilles: cooking and traffic as drivers of spatial variations in exposure to particulate matter by Prof. Albert Presto, Carnegie Mellon
"Sharp spatial gradients of particulate matter (PM), organic aerosol (OA), and black carbon (BC) concentrations exist at intra-city scales (<1 km) due to intense emissions from sources like traffic and cooking activities. Typical stationary deployment of samplers is not capable of resolving these spatial gradients. By deploying an Aerodyne Aerosol Mass Spectrometer (AMS) and other high temporal resolution measurements on a mobile sampling platform, we are able to investigate the spatial variation of PM mass concentration, PM composition, and particle number concentrations within cities. Source apportionment with Positive Matrix Factorization (PMF) enables identification of contributions of traffic and other sources to the observed PM mass. Cooking and traffic sources dominate PM spatial variability.
This presentation will show results for two cities: Pittsburgh and Oakland. In locations with high local source impact in Pittsburgh, the PM1 concentration is 2 mg m-3 (40%) higher than urban background locations. Traffic emissions are the largest source contributing to population-weighted exposures to primary PM. The concentration of both cooking and traffic PM are positively correlated to their respective geographical covariates: vehicle-miles travelled (VMT) and restaurant count. VMT is a reliable predictor for traffic PM concentrations for use in air pollutant spatial models. Restaurant count is an imperfect predictor for cooking PM concentration, likely due to the highly variable emissions of individual restaurants. Cooking PM is also positively correlated to VMT, which suggests that near-road cooking emissions can be misattributed to traffic sources in the absence of PM source apportionment. In Pittsburgh, 27.7% and 8.9% of the total population are exposed to >1 mg m-3 of traffic- and cooking-related primary emissions, with some populations exposed to high concentrations from both sources. Results for Oakland show similar spatial patterns and concentration trends. While these data were collected for two cities, the source mix in many U.S. cities is similar. We therefore expect similar PM spatial patterns and increased exposures in high-source areas nationwide."