AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Contrasting the Oxidation Behavior of Aerosols in Urban and Rural Locations
RISHABH SHAH, Kalliopi Florou, Albert A. Presto, Carnegie Mellon University
Abstract Number: 200 Working Group: Aerosol Chemistry
Abstract We present direct and oxidized measurements of atmospheric aerosol in a rural and an urban case location. The rural case location is the remote village of Finokalia on Crete island, Greece. Finokalia is characterized by highly oxidized and stable organic aerosol, with air masses coming from different sources (dust from Sahara Desert, marine aerosol over the Mediterranean Sea, urban pollution from mainland Europe).
An oxidative flow reactor (OFR) is used for simulating oxidation of sampled aerosol. Size distribution and chemical composition of ambient and OFR-oxidized aerosol particles are measured using a scanning mobility particle sizer (SMPS) and high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Using National Oceanic and Atmospheric Administration’s Lagrangian trajectory model (HYSPLIT), we estimate the source of air parcels received in Finokalia during sampling. We find that (a) ambient aerosol on all days of sampling is highly oxidized (indicated by elemental O:C=0.9 and H:C=1.5 ratios); (b) irrespective of whether air parcels come from mainland Europe or simply over the sea, several days’ worth of simulated aging in the OFR only yields mass enhancements as high as 1.6; (c) when the air parcels are received from mainland Europe, the oxidation state of particles increases upon processing in the OFR – a behavior not observed when air parcels are transported completely from marine environments.
The next stage of our project is to conduct similar experiments in an urban case location (Pittsburgh, PA) in May-June, 2017. Sampling locations selected within the city will include areas influenced by different emission sources e.g., near-road, industry and suburban background. We believe that contrasting the results obtained in Pittsburgh against those from Finokalia will inform on the oxidation mechanisms of urban and semi-urban aerosol in the atmosphere.