AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Characterizing the Near-road Submicron Aerosols Near a North Carolina Interstate Freeway: Summer Vs. Winter Observations
PROVAT SAHA, Andrey Khlystov, Andrew Grieshop, North Carolina State University
Abstract Number: 479 Working Group: Urban Aerosols
Abstract Motor vehicles are a dominant source of primary and secondary submicron particulate matter (PM) in urban areas. There are steep gradients in concentrations of primary gas- and particle-phase species, including black carbon (BC), organic aerosols (OA) and other species within 10s to 100s of meters from the roadway. Here, we present a comprehensive near-road submicron aerosol characterization effort from summer and winter field campaigns at a site near Interstate 40, outside Durham, North Carolina. Month-long measurement campaigns were performed in summer 2015 and winter 2016 and involved detailed measurements at: (i) a fixed near-road site located within 10 m from highway, (ii) an upwind background site, and (iii) during downwind transects on a minor roadway perpendicular to highway when wind directions were favorable. Measurements include submicron aerosol chemical composition, size distributions, and volatility using a multi-tube thermodenuder (TD), black carbon, NOx, meteorological conditions and traffic data. A van is equipped for transects measurement with various aerosols and gaseous instruments and a multi-tube TD and consecutively sample at different distances (15, 50, 100, 150, 220 m) downwind of the highway and repeated several times a day. Preliminary results show strong seasonal and diurnal differences in spatial distribution of traffic-sourced pollutants. Strong signature of vehicles emission was observed within 100-150 m from highway edge with significantly higher concentration at morning. Less-sharp near-road gradients are observed in winter in many species. Particle volatility measurements show that traffic-sourced ultrafine particles evaporate at lower temperatures than background aerosol in both seasons. Transect measurements of particle evaporation show that this behavior evolves with downwind transport. The observed spatial patterns appear to be moderated by temperature, winds, mixing height, traffic. Detailed observations from summer and winter campaigns will be presented.