Source apportionment of the summer time carbonaceous aerosol at Nordic rural background sites
1Norwegian Institute for Air Research (NILU), P.O. Box 100, 2027 Kjeller, Norway
2EMEP MSC-W, Norwegian Meteorological Institute, 0313 Oslo, Norway
3Dept. Earth and Space Sciences, Chalmers University of Technology, 41296 Gothenburg, Sweden
4Department of Atmospheric Environment, Faculty of Science and Technology, Aarhus University, P.O. Box 358, 4000 Roskilde, Denmark
5Department of Chemistry, Aarhus University, 8000 Aarhus C, Denmark
6Lund University, Department of Physics, Division of Nuclear Physics, Lund, Sweden
7Finnish Meteorological Institute, Air Quality, P.O. Box 503, 00101 Helsinki, Finland
8Vienna University of Technology, Vienna, Austria
9US Environmental Protection Agency, 109 T. W. Alexander Drive, Research Triangle Park, North Carolina, USA
10Alion Science and Technology, Box 12313, Research Triangle Park, North Carolina, USA
Abstract. 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 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.