AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Aerosol Composition at a Rural Site Southeast of London Measured by High Resolution Mass Spectrometry
NGA LEE NG, Lu Xu, Matthew Kollman, John Jayne, Scott Herndon, William Brooks, Leah Williams, Paola Massoli, Edward Fortner, Puneet Chhabra, Timothy Onasch, Douglas Worsnop, Georgia Institute of Technology
Abstract Number: 446 Working Group: Urban Aerosols
Abstract A High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and complementary instrumentations are deployed at a rural site in Detling (southeast of London) during the Clear Air for London (ClearfLo) campaign from January – February 2012. ClearfLo is a collaborative multidisciplinary project to study boundary layer pollution across London. The HR-ToF-AMS provides quantitative measurement of non-refractory submicron aerosol composition and size distribution with high time resolution. Total mass concentrations and diurnal trends of organics, nitrate, sulfate, ammonium, and chloride at the Detling sampling site are reported. It is found that air mass from the East (continental Europe) is characterized by high loadings, especially high nitrate. As increasing distance from an urban center is often correlated with increasing photochemical aging, the aerosol mass spectrometry data at the Detling site provide insights into composition of a more oxidized air mass and the evolution of organic aerosols (OA) in the atmosphere. Elemental analyses are performed to determine elemental composition of the bulk OA, including oxygen/carbon (O/C), hydrogen/carbon (H/C), and nitrogen/carbon (N/C) ratios. Positive matrix factorization (PMF) is used to deconvolve the OA into different components, reflecting OA of different sources and/or photochemical processing. Preliminary PMF analysis resolved three factors: hydrocarbon-like organic aerosols (HOA, surrogate for POA) and oxygenated organic aerosols (OOA, surrogate for SOA), and biomass burning OA (BBOA). Analysis of thermodenuder data revealed the presence of very non-volatile SOA components, with a thermodenuder temperature of 250 oC, the compounds remaining has an O/C of ~1.