Environmental & Climate Sciences Department Seminar

"What's happening in near-road air quality? Insights from a recent field study near a North Carolina Interstate freeway"

Presented by Provat Saha, North Carolina State University

Thursday, January 12, 2017, 11:45 am — Conference Room Bldg 815E

Motor vehicles emit gas- and particle-phase air pollutants, including organic and inorganic gasses, black carbon (BC), organic aerosols (OA) and other species, which are linked with adverse human health effects, visibility reductions, and climate effects. There are steep gradients in concentrations of these species within 10s to 100s of meters from the roadway. The mechanistic evolution of vehicle emissions downwind of a roadway involves complex physicochemical processes and varies spatially and temporally. Exposure concentrations of different pollutants in a near-road environments are influenced by the complex dispersion process, built environments and meteorological factors which lead to physicochemical transformations of primary reactive species. For a better understanding of exposure and evolution of near-road air pollutants, we conducted a comprehensive field study at a site near Interstate 40, near Durham, North Carolina. The specific aims of this study were: 1) characterizing the spatio-temporal and seasonal trends of multiple air pollutant concentrations in a near highway setting, 2) characterizing near-road submicron aerosol volatility and mixing state, and 3) determining the extent to which motor vehicles contribute to ambient secondary OA production. Results from this study show strong seasonal and diurnal differences in downwind concentration gradients with a less-sharp near-road gradients in winter in many species, decreasing of the semi-volatile fraction in ultrafine particle with downwind distance, and a substantial seasonal differences in secondary OA (SOA) formation due to oxidation of near-highway air in an oxidation flow reactor. Details observations from this field study will be discussed.
This talk may also briefly address two other projects those are part of my Ph.D. work, (i) improve quantification of gas-particle partitioning parameter values of organic aerosol using a dual-thermodenuder system, and (ii) laboratory aging of wood smoke from d

Hosted by: Jian Wang

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