Presentations and Publications
Millet, D.B., Donahue, N.M., Pandis, S.N., Polidori, A., Stanier, C.O., Turpin, B.J., Goldstein, A.H., “Atmospheric volatile compound measurement during the Pittsburgh Air Quality Study: Results, interpretations, and quantification of primary and secondary contributions”, Journal of Geophysical Research – Atmospheres, Vol 110(D07S07), 2005, doi:10.1029/2004JD004601.
Primary and secondary contributions to ambient levels of volatile organic compounds
(VOCs) and aerosol organic carbon (OC) are determined using measurements at the
Pittsburgh Air Quality Study (PAQS) during January–February and July–August 2002.
Primary emission ratios for gas and aerosol species are defined by correlation with
species of known origin, and contributions from primary and secondary/biogenic sources
and from the regional background are then determined. Primary anthropogenic
contributions to ambient levels of acetone, methylethylketone, and acetaldehyde were
found to be 12–23% in winter and 2–10% in summer. Secondary production plus
biogenic emissions accounted for 12–27% of the total mixing ratios for these compounds
in winter and 26–34% in summer, with background concentrations accounting for the
remainder. Using the same method, we determined that on average 16% of aerosol OC
was secondary in origin during winter versus 37% during summer. Factor analysis of the
VOC and aerosol data is used to define the dominant source types in the region for both
seasons. Local automotive emissions were the strongest contributor to changes in
atmospheric VOC concentrations; however, they did not significantly impact the aerosol
species included in the factor analysis. We conclude that longer-range transport and
industrial emissions were more important sources of aerosol during the study period. The
VOC data are also used to characterize the photochemical state of the atmosphere in the
region. The total measured OH loss rate was dominated by nonmethane hydrocarbons
and CO (76% of the total) in winter and by isoprene, its oxidation products, and
oxygenated VOCs (79% of the total) in summer, when production of secondary organic
aerosol was highest.