Articles | Volume 17, issue 21
Research article
08 Nov 2017
Research article |  | 08 Nov 2017

Long-term chemical analysis and organic aerosol source apportionment at nine sites in central Europe: source identification and uncertainty assessment

Kaspar R. Daellenbach, Giulia Stefenelli, Carlo Bozzetti, Athanasia Vlachou, Paola Fermo, Raquel Gonzalez, Andrea Piazzalunga, Cristina Colombi, Francesco Canonaco, Christoph Hueglin, Anne Kasper-Giebl, Jean-Luc Jaffrezo, Federico Bianchi, Jay G. Slowik, Urs Baltensperger, Imad El-Haddad, and André S. H. Prévôt

Abstract. Long-term monitoring of organic aerosol is important for epidemiological studies, validation of atmospheric models, and air quality management. In this study, we apply a recently developed filter-based offline methodology using an aerosol mass spectrometer (AMS) to investigate the regional and seasonal differences of contributing organic aerosol sources. We present offline AMS measurements for particulate matter smaller than 10 µm at nine stations in central Europe with different exposure characteristics for the entire year of 2013 (819 samples). The focus of this study is a detailed source apportionment analysis (using positive matrix factorization, PMF) including in-depth assessment of the related uncertainties. Primary organic aerosol (POA) is separated in three components: hydrocarbon-like OA related to traffic emissions (HOA), cooking OA (COA), and biomass burning OA (BBOA). We observe enhanced production of secondary organic aerosol (SOA) in summer, following the increase in biogenic emissions with temperature (summer oxygenated OA, SOOA). In addition, a SOA component was extracted that correlated with an anthropogenic secondary inorganic species that is dominant in winter (winter oxygenated OA, WOOA). A factor (sulfur-containing organic, SC-OA) explaining sulfur-containing fragments (CH3SO2+), which has an event-driven temporal behaviour, was also identified. The relative yearly average factor contributions range from 4 to 14 % for HOA, from 3 to 11 % for COA, from 11 to 59 % for BBOA, from 5 to 23 % for SC-OA, from 14 to 27 % for WOOA, and from 15 to 38 % for SOOA. The uncertainty of the relative average factor contribution lies between 2 and 12 % of OA. At the sites north of the alpine crest, the sum of HOA, COA, and BBOA (POA) contributes less to OA (POA / OA  =  0.3) than at the southern alpine valley sites (0.6). BBOA is the main contributor to POA with 87 % in alpine valleys and 42 % north of the alpine crest. Furthermore, the influence of primary biological particles (PBOAs), not resolved by PMF, is estimated and could contribute significantly to OA in PM10.

Short summary
We present offline AMS analyses for the organic aerosol (OA) in PM10 at nine sites in central Europe for 2013. Primary OA is separated into traffic, cooking, and wood-burning components. A factor explaining sulfur-containing ions, with an event-driven time series, is also separated. We observe enhanced production of secondary OA (SOA) in summer, following biogenic emissions with temperature. In winter a SOA component is dominant, which correlates with anthropogenic inorganic species.
Final-revised paper