Source apportionment of organic aerosol and ozone and the effects of emission reductions

• Published in: Atmospheric environment (1994) 2019-02, Vol.198, p.89-101
• Main Authors: Dunker, Alan M., Koo, Bonyoung, Yarwood, Greg
• Format: Article
• Language: English
• Subjects: CAMx; Houston; Ozone; Secondary organic aerosol; Source apportionment; Volatility basis set
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2018.10.042

Formation of organic aerosol (OA) and ozone were simulated for the greater Houston area in September 2013 and 2028 (summer conditions) using the Comprehensive Air Quality Model with Extensions (CAMx). We also simulated the background concentrations in the absence of US anthropogenic emissions. The 1.5-dimensional volatility basis set scheme was used to represent formation of primary and secondary OA (POA and SOA). The path-integral method for source apportionment was successfully extended to OA formation using the same numerical approach previously used for ozone and then applied to apportion the anthropogenic increment of OA and ozone to six emission source categories. The anthropogenic increment is the difference between the 2013 or 2028 simulation and the background simulation. Averaged over 21 air monitoring sites in Houston, point sources make the largest contribution to monthly average SOA and OA (25%–37%, depending on year) and to monthly maximum 8-h ozone (21%–26%). Onroad and then nonroad sources are the next most important in 2013, but their contributions diminish by 2028. The sources’ contributions to SOA correlate much more strongly with their NOx emissions than with their emissions of organic precursor species. Anthropogenic emissions enhance OA formation from biogenic emissions, and this enhancement is 46% and 48% of the total OA concentration in Houston in 2013 and 2028, respectively. Point sources make the largest contribution to the enhancement. Additional results for a larger regional area covering Texas and nearby states are also presented. [Display omitted] •Point sources are the largest anthropogenic contributor to SOA and O3 in Houston.•NOx emissions are a principal factor in a source's contribution to SOA.•SOA from biogenic emissions is strongly enhanced by anthropogenic emissions.•The path-integral method is extended to source apportionment of SOA and OA.