AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Overview of Surface Measurements of Submicron Particulate Matter in the Greater Houston Area during the DISCOVER-AQ 2013 Field Campaign
YU JUN LEONG, Nancy Sanchez, Henry Wallace, Basak Karakurt Cevik, James Flynn, Yan Han, Paola Massoli, Cody Floerchinger, Edward Fortner, Scott Herndon, Barry Lefer, Robert Griffin, Rice University
Abstract Number: 137 Working Group: Urban Aerosols
Abstract Submicron particulate matter (PM$_1) has strong climate and health impacts and remains poorly characterized, particularly in the industrialized city of Houston. Semi-Lagrangian and factor analyses were applied to non-refractory PM$_1 chemical composition data collected in September 2013 during the DISCOVER-AQ field mission in Houston, TX. Submicron PM and trace-gas measurements made using the University of Houston/Rice and Aerodyne Research, Inc. mobile laboratories were analyzed for spatial trends, focusing on PM$_1 chemical composition measured by high-resolution time-of-flight aerosol mass spectrometers (HR-ToF-AMS). Applying a two-step cluster analysis on PM$_1 composition data, the Houston area was divided into three pollution zones with distinct PM$_1 chemical composition and photochemical age: Zone 1 in the northwestern forested residential area, Zone 2 in central metropolitan Houston, and Zone 3 in the southeastern industrial/ship channel area. A semi-Lagrangian analysis was conducted using HR-ToF-AMS PM$_1 datasets collected by the two mobile laboratories to characterize the aging and transformation processes of PM$_1 during downwind transport. Positive Matrix Factorization (PMF) of organic aerosol (OA) mass spectral data collected by the HR-ToF-AMS yielded at least three distinct OA factors. The first OA factor represents fresh primary aerosol; it is elevated on roadways and near industrial sources. The second and third OA factors are oxygenated OA (OOA-1, OOA-2) factors that have distinct mass spectra. The less-aged and semi-volatile OOA-1 factor is ubiquitous throughout Houston and is likely secondary OA (SOA) that is produced locally, while the processed and less volatile OOA-2 factor has higher spatial variability and likely represents SOA from long-range transport. The OOA-1 factor dominates total averaged OA mass in Zone 1 (59%) and Zone 3 (68%), indicating strong SOA influence from biogenic and anthropogenic precursor emissions in each respective zone. Zone 2 shows highest OOA-2 influence (26%) likely due to aged outflow influence from other zones.