10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Influence of Future Emission Reductions on Source Apportionment of Organic Aerosol in the Houston Region

BONYOUNG KOO, Alan Dunker, Greg Yarwood, Ramboll

     Abstract Number: 591
     Working Group: Source Apportionment

Abstract
Organic aerosol (OA) accounts for a significant fraction of atmospheric fine particulate matter (PM) mass. OA can be directly emitted into the atmosphere (primary OA, POA) or formed secondarily from hydrocarbon precursors (secondary OA, SOA). SOA yields are modulated by concentrations of NO and SO2 which have anthropogenic sources that change in response to our activities and policies. NOx has direct and indirect effects on SOA formation: a direct effect is that SOA yields depend on NOx; an indirect effect is that species which oxidize hydrocarbon precursors to SOA (e.g., OH and NO3 radicals) also depend on NOx. Therefore, accurate source apportionment of SOA requires a methodology that properly takes into account both the direct and indirect effects. Tagged species methods currently available in photochemical grid models do not account for the indirect effects. A recently developed source apportionment approach called the Path-Integral Method (PIM) provides rigorous source contributions by integrating the first-order sensitivity of pollutant concentrations to emissions computed at several emission levels. The PIM can be applied for any species included in the chemical mechanism, has a mathematically rigorous methodology, and allows the numerical accuracy of the method implementation to be checked for each application. The PIM has been successfully used to compute source contributions of gaseous pollutants such as ozone, NO2 and aldehydes. Here, we apply the PIM to determine contributions of US anthropogenic source sectors to OA in the Houston, Texas region, accounting for both direct and indirect effects of NOx emissions on SOA formation. Two emission scenarios (2013 base year and 2028 projected future year) are used to examine how future emission reductions influence the source apportionment of OA in the region.