AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Anthropogenic and Biogenic Contributions to Secondary Organic Aerosols at two Industrial Cities in the Upper Midwest
ANDREW RUTTER, David Snyder, Elizabeth Stone, Brandon Shelton, Jeff Deminter, James Schauer, University of Wisconsin-Madison
Abstract Number: 604 Working Group: Source Apportionment
Abstract Contributions of anthropogenic and biogenic secondary organic carbon (SOC) to total PM2.5 mass are of interest to air quality management agencies required to demonstrate maintenance of the PM2.5 NAAQS. Currently, quantitative tools to understand the SOC source contributions to PM2.5 mass are not well developed, and the spatial variation of different types of SOC is not known.
In this study concentrations of anthropogenic and biogenic SOC mass were determined using PM2.5 measurements made in Cleveland, OH and Mingo Junction, OH. Organic molecular markers for anthropogenic and biogenic SOC were extracted from the PM2.5 and analyzed by GC-MS. Source apportionment calculations were conducted using the EPA CMB (v.8.2) software.
Calculated SOC concentrations from SOC tracers followed the expected seasonal patterns with maximum contributions during the summer and minimum contributions during the winter. Anthropogenic SOC constituted approximately 37% to the apportioned SOC and 6% to the measured OC, on average across both sites. Biogenic SOC contributed the 42% to the apportioned SOC, and 4% to the measured OC. Anthropogenic SOC contributed strongly to organic PM2.5 meaning that SOC may by partially controllable by reductions in VOC emissions from anthropogenic sources.
Similarities in the month-to-month patterns in alpha-pinene markers were observed between Cleveland and Mingo Junction, suggesting a regional character to this type of SOC. However, such patterns were not readily apparent in the isoprene markers. Comparisons between SOC apportionments from the CMB modeling and measurements of non-biomass burning water soluble organic carbon (NB-WSOC) revealed that approximately half of the NB-WSOC during spring, summer and early fall could not be apportioned with the SOC markers available during this study. This suggested that additional sources not included in the CMB model used in this study contributed to SOC, or that models using markers measured in chamber oxidations are not representative of the study sites.