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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 110, D07S07, doi:10.1029/2004JD004601, 2005

Atmospheric volatile organic compound measurements during the Pittsburgh Air Quality Study: Results, interpretation, and quantification of primary and secondary contributions

Dylan B. Millet

Division of Ecosystem Sciences, University of California, Berkeley, California, USA


Neil M. Donahue

Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA


Spyros N. Pandis

Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA


Andrea Polidori

Department of Environmental Sciences, Rutgers University, New Brunswick, New Jersey, USA


Charles O. Stanier


Barbara J. Turpin

Department of Environmental Sciences, Rutgers University, New Brunswick, New Jersey, USA


Allen H. Goldstein

Division of Ecosystem Sciences, University of California, Berkeley, California, USA


Abstract

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.

Received 3 February 2004; accepted 22 April 2004; published 25 January 2005.

Keywords: volatile organic compounds; aerosols; PAQS.

Index Terms: 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 0345 Atmospheric Composition and Structure: Pollution: urban and regional (0305, 0478, 4251).

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Citation: Millet, D. B., N. M. Donahue, S. N. Pandis, A. Polidori, C. O. Stanier, B. J. Turpin, and A. H. Goldstein (2005), Atmospheric volatile organic compound measurements during the Pittsburgh Air Quality Study: Results, interpretation, and quantification of primary and secondary contributions, J. Geophys. Res., 110, D07S07, doi:10.1029/2004JD004601.