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Source Apportionment of the Summer Time Carbonaceous Aerosol at Nordic Rural Background Sites
Yttri, K. E., D. Simpson, J. K. Nojgaard, K. Kristensen, J. Genberg, K. Stenstrom, E. Swietlicki, R. Hillamo, M. Aurela, H. Bauer, J. H. OFFENBERG, M. JAOUI, C. Dye, S. Eckhardt, J. F. Burkhart, A. Stohl, AND M. Glasius. Source Apportionment of the Summer Time Carbonaceous Aerosol at Nordic Rural Background Sites. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, Germany, 11(24):13339-13357, (2011).
The National Exposure Research Laboratory′s (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA′s mission to protect human health and the environment. HEASD′s research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA′s strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
In the present study, natural and anthropogenic sources of particulate organic carbon (OCp) and elemental carbon (EC) have been quantified based on weekly filter samples of PM10 (particles with aerodynamic diameter <10µ collected at four Nordic rural background sites (Birkenes (Norway), Hyytiälä Finland) Vavihill (Sweden), Lille Valby (Denmark») during late summer (5 August- 2 September 2009). Levels of source specific tracers, i.e. cellulose, levoglucosan, mannitol and the 14C/12C ratio of total carbon (TC), have been used as input for source apportionment of the carbonaceous aerosol, whereas Latin Hypercube Sampling (LHS) was used to statistically treat the multitude of possible combinations resulting from this approach. The carbonaceous aerosol (here: TCp; i.e. particulate TC) was totally dominated by natural sources (69-86 %), with biogenic secondary organic aerosol (BSOA) being the single most important source (48-57 %). Interestingly, primary biological aerosol particles (PBAP) were the second most important source (20-32 %). The anthropogenic contribution was mainly attributed to fossil fuel sources (OCff and ECff) (10-24%), whereas no more than 3-7% was explained by combustion of biomass (OCbb and ECbb) in this late summer campaign i.e. emissions from residential wood burning and/or wild/agricultural fires. Fossil fuel sources totally dominated the ambient EC loading, accounting for 4-12% of TCp, whereas <1.5% was attributed to combustion of biomass. The carbonaceous aerosol source apportionment showed only minor variation between the four selected sites. However, Hyytiälä and Birkenes showed greater resemblance to each other, as did Lille Valby and Vavihill, the two latter being somewhat more influenced by anthropogenic sources. Ambient levels of organosulphates and nitrooxy-organosulphates in the Nordic rural background environment are reported for the first time in the present study. The most abundant organosulphate compounds were an organosulphate of isoprene and nitrooxy-organosulphates of α-and β-pinene and limonene.
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Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
HUMAN EXPOSURE AND ATMOSPHERIC SCIENCES DIVISION
PROCESS MODELING RESEARCH BRANCH