AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Contribution of Bioaerosols to PM10 and PM2.5 in the Southeastern United States
TRACI LERSCH, Gary Casuccio, Stephanie Shaw, Annette Rohr, RJ Lee Group, Inc.
Abstract Number: 270 Working Group: Bioaerosols
Abstract The nature and origin of carbonaceous aerosols and their contribution to ambient particulate matter (PM) mass were evaluated to better understand the contribution of bioaerosols to ambient air quality. Ambient PM10 and PM2.5 samples were collected in Atlanta and Yorkville, GA as part of the Southeastern Aerosol Research and Characterization Study (SEARCH). The 2010 sampling program was conducted at both an urban and a rural site to provide insight on the seasonal influences of bioaerosols. The ChemPass Personal Environmental Monitoring System (PEMS) developed by the Harvard School of Public Health was used to collect the samples over 24 hour periods.
Single particle morphology and compositional information from scanning electron microscopy (SEM) were applied to measure primary particle mass concentrations. SEM methods were used to quantify and speciate carbonaceous aerosols based on distinctive morphological features and trace characteristic elements. Particle volume and density were estimated and used to calculate the mass of bioaerosols, elemental carbon (soot), and other particle constituents. In addition, samples were subjected to thermal-optical reflectance (TOR) analysis to quantify total (TC) and organic carbon (OC).
SEM carbon measurements were compared to TOR results of co-located filters. On average, the PM10-2.5 TC SEM results were within 10% of the PM10-2.5 TC TOR measurements. Biological aerosols were a significant component of PM10-2.5 at the urban and rural sites during the spring and fall 2010 campaigns. The average weight percent of vegetative particles ranged from 8.7 to 18.4 percent at the urban and rural sites, respectively. However, the SEM underestimated the OC in the PM2.5 fraction. The difference may be due, in part, to the loss of volatiles over time. Further examination of the filters using high resolution SEM detected carbon-rich deposits under specific operating conditions. Given reasonable assumptions, these deposits could account for the ‘missing’ PM2.5 carbon mass in the SEM analysis as compared to the TOR data on the co-located filters.