AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Quantitative Analysis of Long-term Source Contributions to the Organic Aerosol in Switzerland
KASPAR RUDOLF DAELLENBACH, Giulia Stefenelli, Imad El Haddad, Carlo Bozzetti, Athanasia Vlachou, Paula Fermo, Raquel Gonzalez, Andrea Piazzalunga, Christina Colombi, Francesco Canonaco, Jay Slowik, Urs Baltensperger, Andre Prévôt, Paul Scherrer Institute
Abstract Number: 310 Working Group: Source Apportionment
Abstract Field deployments of the aerosol mass spectrometer have advanced the measurement of organic aerosol. Subsequent application of positive matrix factorization quantifies the contribution of primary emissions sources as biomass burning (BBOA), traffic, cooking and oxygenated OA, qualified as secondary OA (SOA). However, investigation of regional and seasonal differences by systematic long-term deployment of the AMS on a dense measurement network is impractical because of instrument cost and maintenance requirements. To overcome these limitations and to access also coarse particulate matter (PM), we have developed a method of using the AMS for the analysis of conventional aerosol filters collected worldwide. The analysis consists of water extraction of PM and subsequent atomization of the resulting solutions into the AMS. The recovery of bulk organics is approximately 70% and the retrieved mass spectra are comparable to the corresponding online measurements.
We present offline PM10 AMS measurements at 9 stations in Switzerland with different exposure characteristics for the entire year of 2013 (819 samples). Source contributions are combined with back-trajectory analysis for the determination of source regions. We demonstrate that the dominant factors governing air quality can be region-specific, e.g. BBOA is strongly enhanced in alpine valleys relative to urban centers. We observe the production of SOA in summer, following the increase in biogenic emissions with temperature. Also a highly aged SOA, prominent in winter, could be extracted. This factor correlates with anthropogenic secondary inorganic species and is most notably perceived when the site is affected by air masses from continental Europe; it could therefore be related to long-range transport. These results are also compared to laser-desorption/ionization mass spectrometry analyses for further insights in the chemical nature of the aerosol. We will present this thorough assessment of the local and regional sources affecting the air quality during winter and summer at the different sites.