Preprints
https://doi.org/10.5194/acp-2022-648
https://doi.org/10.5194/acp-2022-648
 
19 Sep 2022
19 Sep 2022
Status: this preprint is currently under review for the journal ACP.

Predicted and Observed Changes in Summertime Biogenic and Total Organic Aerosol in the Southeast United States from 2001 to 2010

Brian T. Dinkelacker1, Pablo Garcia Rivera1, Ksakousti Skyllakou2, Peter J. Adams3,4, and Spyros N. Pandis2,5 Brian T. Dinkelacker et al.
  • 1Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213
  • 2Institute of Chemical Engineering Sciences (FORTH/ICE-HT), 26504, Patras, Greece
  • 3Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213
  • 4Department of Engineering and Public Policy, Carnegie Mellon University, Pittsburgh, PA, 15213
  • 5Department of Chemical Engineering, University of Patras, 26500, Patras, Greece

Abstract. Biogenic secondary organic aerosol (bSOA) is a major component of atmospheric particulate matter (PM2.5) in the southeast United States especially during the summer, when emissions of biogenic volatile organic compound (VOCs) are high and emissions from anthropogenic sources enhance the formation of secondary particulate matter. We evaluate the performance of PM2.5 organic aerosol predictions by a chemical transport model (PMCAMx) in response to significant changes in anthropogenic emissions during the summers of 2001 and 2010. Average predicted bSOA concentrations in the southeast US did not change appreciably from the summer of 2001 to the summer of 2010, while the anthropogenic SOA decreased by 45 %. As a result, the biogenic fraction of total OA increased from 0.46 in 2001 to 0.63 in 2010. Partitioning effects due to reduced anthropogenic OA from 2001 resulted in 0.4 µg m-3 less biogenic OA on average in the southeast US in the summer of 2010. This was offset by biogenic SOA increases due to higher biogenic vapor emissions in the warmer 2010 summer. Little noticeable difference was observed in OA prediction performance in the southeast US between the two summer simulation periods. The fractional error of OA predictions remained practically the same (0.41 and 0.44 at CSN sites and 0.40 to 0.41 at IMPROVE sites in the summers of 2001 and 2010 respectively). The fractional bias of OA predictions increased from 0.10 to 0.22 at CSN sites and decreased from 0 to -0.09 at IMPROVE sites between the two periods. Removing the NOx-dependence of SOA formation yields resulted in higher fractional error and fractional bias at both CSN and IMPROVE sites in both summer periods, demonstrating the efficacy of the current formulation of SOA yields. Our analysis suggests that the changes in biogenic OA in this forested relatively polluted region appear to be dominated by the partitioning effects and the NOx effects on SOA yields.

Brian T. Dinkelacker et al.

Status: open (until 31 Oct 2022)

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Brian T. Dinkelacker et al.

Brian T. Dinkelacker et al.

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Short summary
A number of factors have influenced the biogenic secondary organic aerosol (SOA) levels in the southeastern US from 2001 to 2010. The increases in temperature have led to an increase of the emissions of biogenic volatile organic compounds by trees and a corresponding increase of the SOA. However, this increase has been balanced by the reductions in the anthropogenic emissions of organic gases and particulate matter as well as of the oxides of nitrogen keeping the biogenic SOA roughly constant.
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