AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Volatility of Ambient Organic Aerosol at an Urban and a Remote Site in Europe
ANDREA PACIGA, Lea Hildebrandt Ruiz, Gabriella Engelhart, Evangelia Kostenidou, Monica Crippa, Andre Prévôt, Urs Baltensperger, Spyros Pandis, Carnegie Mellon University
Abstract Number: 368 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract The composition and volatility of ambient organic aerosol were measured in a major urban (Paris, France) and a remote area (Finokalia, Greece) during five month-long campaigns. The measurements were performed combining CMU’s variable residence-time thermodenuder, the Aerodyne Aerosol Mass Spectrometer and a Scanning Mobility Mass Spectrometer.
The OA measurements in Paris were part of the MEGAPOLI campaigns and were collected in the summer of 2009 and winter of 2010, providing contrasting meteorological conditions. During the summer the OA concentrations were relatively low, with mostly aged OA that was transported to the site from other areas. Half of the OA evaporated at 90 degrees Celsius and 90 percent at 190 Celsius at a centerline residence time of 25 seconds. During the winter the OA levels were higher with local sources becoming more important. The OA volatility was higher than in the summer with half of the OA evaporating at 80 degrees Celsius.
The most recent FAME campaign took place in October 2011 in a remote site on the island of Crete, Greece. This dataset is added to the collection of studies at Finokalia performed during the summer of 2008 and winter of 2009. This particular site is far from local emission sources, allowing the aerosol to reach a highly aged, oxygenated state. During periods with intense sunlight the aged OA has quite low volatility (requiring a temperature of 120 degrees Celsius to evaporate half of its mass at a centerline residence time of 15 seconds). During periods with lower photochemical activity the OA volatility increased with half the OA evaporating at 100 degrees Celsius.
A dynamic mass transfer model is used to estimate the OA volatility distribution for the different areas and seasons, evaluating changes in O:C of the OA, photochemical conditions, and OA sources (using positive matrix factorization).