Open AccessChemical characteristics of North American surface layer outflow: Insights from Chebogue Point, Nova Scotia
Author(s) -
Millet Dylan B.,
Goldstein Allen H.,
Holzinger Rupert,
Williams Brent J.,
Allan James D.,
Jimenez José L.,
Worsnop Douglas R.,
Roberts James M.,
White Allen B.,
Hudman Rynda C.,
Bertschi Isaac T.,
Stohl Andreas
Publication year - 2006
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2006jd007287
Subject(s) - aerosol , outflow , environmental science , nova scotia , pollution , ozone , atmospheric sciences , trace gas , air pollution , chemical composition , air mass (solar energy) , pollutant , environmental chemistry , boundary layer , oceanography , chemistry , meteorology , geology , geography , physics , ecology , organic chemistry , biology , thermodynamics
We present a factor analysis‐based method for differentiating air masses on the basis of source influence and apply the method to a broad suite of trace gas and aerosol measurements collected at Chebogue Point, Nova Scotia, during the summer of 2004 to characterize the chemical composition of atmospheric outflow from eastern North America. CO, ozone, and aerosol mass were elevated by 30%, 56%, and more than 300% at Chebogue Point during U.S. outflow periods. Organic aerosol mass was highest during U.S. pollution events, but made up the largest fraction (70%) of the total aerosol during periods of primary and especially secondary biogenic influence, indicating the importance of both anthropogenic and biogenic organic aerosol. Anthropogenic and oxygenated volatile organic compounds account for the bulk of the gas‐phase organic carbon under most conditions; however, biogenic compounds are important in terms of chemical reactivity. Biogenic emissions thus have a significant impact on the chemistry of air masses downwind of the polluted northeastern United States. Using output from a global 3‐D model of atmospheric composition (GEOS‐Chem), we estimate that CO directly emitted from U.S. pollution sources makes up 28% of the total CO observed at Chebogue Point during U.S. outflow events and 19% at other times, although more work is needed to improve U.S. emission estimates for CO and other pollutants. We conclude that the effects of North American pollution on the chemistry of the western North Atlantic boundary layer are pervasive and not restricted to particular events.