Keith Bein - Interactions between boreal wildfire and urban emissions

Version 1

      Publication Details (including relevant citation   information):

      Bein, K.J., Zhao, Y., Johnston, M.V., and A.S. Wexler (2008),   Interactions between boreal wildfire

           and urban emissions, Journal of   Geophysical Research - Atmospheres, 113(D7), D07304,



      A suite of particulate, gaseous and meteorological measurements   during the Pittsburgh Supersite experiment were used to   characterize the impact of the 2002 Quebec wildfires on pollutant   concentrations and physical and chemical processes dominant in   the region.  Temporal trends in the number distribution of   wildfire particles – isolated using Rapid   Single-ultrafine-particle Mass Spectrometry data – combined with   CO, NOx and O3 mixing ratios identified two   separate periods (Periods I and II) when the measurement site was   directly impacted by plumes of relatively unprocessed wildfire   emissions; i.e. increases in primary ultrafine wildfire   particles, CO and NOx concomitant with a decrease in   O3 from intra-plume NOx titration.    Carbonaceous particle number distributions predominantly   associated with vehicular emissions, PM2.5 sulfate   mass concentration and SO2 mixing ratio resolved   individual components of local and regional sources.  Single   particle signatures indicated a period of intense atmospheric   processing following Period II that caused rapid growth of the   ultrafine mode due to simultaneous sulfate and secondary organic   mass accumulation, resulting in significant changes to particle   physical and chemical properties.  Particle growth was   concurrent with large increases in O3 and maxima in   incoming solar radiation and ambient temperature and is posited   to have occurred in-situ as the air mass, containing a mixture of   urban and wildfire emissions, was advected past the site.    In total, the current work demonstrates significant added   severity for pollution episodes in an area already burdened by   large anthropogenic emission rates due to the impact of the 2002   Quebec wildfires.  High levels of atmospheric processing   increased sulfate accumulation and SOA formation and brought   PM2.5 mass concentrations close to, and O3  mixing ratios in excess of, the National Ambient Air Quality   Standards.  Projections of increasing wildfire activity   under a warming climate may increase the frequency and severity   of such events.

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