AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Chemical Characterization of Organic Aerosol in Greater London Area Using High Resolution Aerosol Mass Spectrometry: Aerosol Volatility and Spatial Distribution
LU XU, Leah Williams, Dominique Young, James Allan, Hugh Coe, Paola Massoli, Edward Fortner, Puneet Chhabra, Scott Herndon, Allison Aiken, Kyle Gorkowski, Manvendra Dubey, Zoe Fleming, Nga Lee Ng, Georgia Institute of Technology
Abstract Number: 287 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract The Clean Air for London (ClearfLo) project aimed to study boundary layer pollution in the greater London area through comprehensive measurements of meteorology, gaseous and particulate composition. Two High-Resolution Time-of-Flight Aerosol Mass Spectrometers (HR-ToF-AMS) were deployed at one rural site (Detling, UK) and one urban site (North Kensington, London, UK) to perform simultaneous characterization of non-refractory submicron particles during winter 2012. The high-temporal resolution comparison between the two sites suggests that the source of sulfate is regional, but the major source of nitrate is local production. The sources of organic aerosol (OA) are more complex. In order to determine the sources of OA, we performed positive matrix factorization (PMF) analysis on the OA mass spectra and resolved multiple OA subtypes, including hydrocarbon-like OA, solid fuel OA, and oxygenated OA. These factors show different behavior between the rural and urban sites.
In addition to the spatial distribution of OA, the volatility of OA was also investigated by using a thermal denuder at the Detling site. An HR-ToF-AMS, a soot-particle AMS (SP-AMS), a single particle soot photometer (SP2), and a scanning mobility particle sizer (SMPS) were deployed in parallel and downstream of the thermal denuder. A large fraction of mass remains in the particle-phase even after thermal-denuding at 250°C. Our instrumentation setup allows us to directly characterize the non-volatile residual at 250°C. In addition, we investigated the relationship between the O:C ratio and OA volatility. On one hand, the O:C ratio of the thermally-denuded OA increases with heating temperature, suggesting that the O:C is inversely correlated with the OA volatility. On the other hand, the mass fraction remaining of OA after heating only shows weak correlation with the O:C of ambient OA, suggesting a lack of relationship between O:C and OA volatility. Possible explanations to these observations will be discussed.