AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Seasonally and Spatially-resolved Source Contributions to Organic Aerosol in Switzerland
Kaspar Daellenbach, Giulia Stefenelli, Imad El Haddad, Carlo Bozzetti, Athanasia Vlachou, Paula Fermo, Raquel Gonzalez, Andrea Piazzalunga, Christina Colombi, JAY SLOWIK, Federico Bianchi, Francesco Canonaco, Urs Baltensperger, Andre Prévôt, Paul Scherrer Institute
Abstract Number: 296 Working Group: Source Apportionment
Abstract Field deployments of the Aerosol Mass Spectrometer (AMS) have advanced the real-time measurement of organic aerosol (OA). Subsequent application of positive matrix factorization (PMF) quantifies the contribution of primary emissions sources such as biomass burning (BBOA), traffic, cooking and secondary oxygenated OA (OOA). However, investigation of regional and seasonal differences by long-term, systematic deployment of the AMS on a dense measurement network is impractical because of instrument cost and maintenance requirements. To overcome these limitations and in order 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 from filters 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). To the best of our knowledge, this is the first spatially resolved long-term AMS dataset. Estimates of source contributions (from PMF) 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 an OOA factor that is dominant in summer and follows the increase in biogenic emissions with temperature. In addition, two long-range transported OOA factors could be extracted, including a winter OOA correlating with anthropogenic secondary inorganic species seen when the site is affected by air masses from continental Europe, and a marine influenced OOA, advected from the Atlantic.