Grantee Research Project Results

Diagnosis of aged prescribed burning plumes impacting an urban area.

Citation:

Lee S, Kim HK, Yan B, Cobb CE, Hennigan C, Nichols S, Chamber M, Edgerton ES, Jansen JJ, Hu Y, Zheng M, Weber RJ, Russell AG. Diagnosis of aged prescribed burning plumes impacting an urban area. Environmental Science & Technology 2008;42(5):1438-1444.

Abstract:

An unanticipated wind shift led to the advection of plumes from two prescribed burning sites that impacted Atlanta, GA, producing a heavy smoke event late in the afternoon on February 28, 2007. Observed PM_2.5 concentrations increased to over 140 microg/m³ and O₃ concentrations up to 30 ppb in a couple of hours, despite the late hour in February when photochemistry is less vigorous. A detailed investigation of PM_2.5 chemical composition and source apportionment analysis showed that the increase in PM_2.5 mass was driven mainly by organic carbon (OC). However, both results from source apportionment and an observed nonlinear relationship between OC and PM_2.5 potassium (K) indicate that the increased OC was not due solely to primary emissions. Most of the OC was water-soluble organic carbon (WSOC) and was dominated by hydrophobic compounds. The data are consistent with large enhancements in isoprenoid (isoprene and monoterpenes) and other volatile organic compounds emitted from prescribed burning that led to both significant O₃ and secondary organic aerosol (SOA) production. Formation of oligomers from oxidation products of isoprenoid compounds or condensation of volatile organic compounds (VOCs) with multiple functional groups emitted during prescribed burning appears to be a major component of the secondary organic contributor of the SOA. The results from this study imply that enhanced emissions due to the fire itself and elevated temperature in the burning region should be considered in air quality models (e.g., receptor and emission-based models) to assess impacts of prescribed burning emissions on ambient air quality.