AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Off-Line Organic Aerosol Analyses of Filter Samples Using Aerosol Mass Spectrometry
IMAD EL HADDAD, Kaspar Dällenbach, Peter Zotter, Jay Slowik, Urs Baltensperger, Andre Prévôt, Paul Scherrer Institute
Abstract Number: 130 Working Group: Source Apportionment
Abstract Field deployments of the Aerodyne Aerosol Mass Spectrometer (AMS) in the last years have advanced the real-time measurement of particle matter. Positive matrix factorization techniques applied on organic aerosol (OA) spectra demonstrate that these contain sufficient information to differentiate several OA sources. These sources include primary emissions from traffic, biomass burning and cooking and oxygenated OA interpreted to be mostly secondary. However, the high cost of the AMS and the complexity of its deployment in certain environments greatly limit the spatial coverage of AMS measurements and make the collection of long-term, continuous datasets not easily achievable. These limitations motivated us to explore the application of laboratory AMS measurements on aerosol filter samples. Such samples are relatively easy and inexpensive to collect and store, and are already routinely collected at many air quality stations worldwide. The approach consists of water or organic solvent extraction of the particulate matter from quartz filters and subsequent atomization of resulting solutions into the AMS. Using only water, we found typically an extraction efficiency of about 70%.
The obtained mass spectra from the off-line analyses were compared to average mass spectra taken from on-line mass spectrometer measurements. We found very similar mass spectra, with correlation coefficients (R2) higher than 0.97. These comparisons were done for both summer and winter samples. Both online and offline methods show for instance higher contributions from m/z related to biomass burning organic aerosol (e.g. m/z 60, 73) and hydrocarbon-like organic aerosol (e.g. m/z55, 57, 69) for the winter sample and higher contributions from OOA-related m/z ratios (e.g. m/z 43, 44) for the summer samples. Further, we will present the first application of this method on filter samples collected at different stations in Switzerland with different exposure characteristics. Source apportionment results using these data will be discussed.