AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Secondary Organic Aerosol Formation at an Urban Downwind Location in Long Island, New York
SHAN ZHOU, Sonya Collier, Jianzhong Xu, Fan Mei, Jian Wang, Yin-Nan Lee, Arthur J. Sedlacek, Stephen Springston, Qi Zhang, University of California, Davis
Abstract Number: 414 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract The US Department of Energy (DOE) sponsored Aerosol Life Cycle Intensive Operational Period field campaign took place at Brookhaven National Laboratory (BNL) at Long Island, New York, from July 1st to August 15, 2011. Here we present measurements from an Aerodyne High-Resolution Time-of-flight Aerosol Mass Spectrometer (HR-AMS), an Ionicon Proton Transfer Reaction Mass Spectrometer, and trace gas detectors to investigate the role of anthropogenic emissions on SOA formation at this urban downwind location. The average mass concentration of non-refractory submicron particles (NR-PM$_1) was 15.3 (±8.9) micro-grams/m$^3, higher than previously observed during summer at New York City (NYC), ~ 50 km to the west of BNL. Organics (64.8%) and sulfate (24.4%) were dominant PM components. Positive Matrix Factorization of the HR-AMS mass spectra indicates that organic aerosol (OA) at BNL was completely secondary in nature, and that there were three distinct secondary OA (SOA) types: (1) a highly oxidized and less-volatile oxygenated OA (LV-OOA; O/C = 0.79); (2) a less oxidized and semi-volatile oxygenated OA (SV-OOA; O/C = 0.41); and (3) a nitrogen-enriched OA (NOA) with an N/C ratio of 0.185. Volatility profiles of OA factors were determined using a thermodenuder upstream of the HR-AMS. SV-OOA accounted for 62% of the OA mass and showed a tight correlation with urban primary emission tracer species such as CO, BC, toluene, and benzene. These anthropogenic emission species all peaked between 7-8 a.m. local time (EDT) at BNL, ~ one-hour later than the peak of traffic emission species (e.g., hydrocarbon-like organic aerosol, CO, and BC) previously observed at NYC. This is an indication that SV-OOA was mainly associated with urban plumes transported from the populous NYC and New Jersey area to the west and southwest of Long Island. Back-trajectory analysis of the air mass source regions corroborates this conclusion. In this presentation, the physical-chemical characteristics and formation processes of SOA will be investigated.