Size-Resolved Source Apportionment of Carbonaceous Particulate Matter in Urban and Rural Sites in the San Joaquin Valley

WALTER HAM (1), Chris Ruehl (1), Michael Kleeman (1)

(1) University of California, Davis

     Abstract Number: 519
     Last modified: May 13, 2010

Abstract
Very little is currently known about the relationship between PM$_(1.8) and PM$_(0.1) source origins and toxicity. The current study presents size resolved source apportionment of PM$_(1.8) and PM$_(0.1) using a molecular marker chemical mass balance (MM-CMB) method at an urban site (Fresno, CA) and rural site (Westside, CA) in central California during the winter and summer months. Micro-Orifice Uniform Deposit Impactors were used to collect ambient PM in six size fractions to determine size distributions of organic carbon (OC), elemental carbon (EC), metals, and a number of trace molecular markers. Diesel engines account for the majority of the PM$_(1.8) and PM$_(0.1) EC in all samples. The majority of OC remains unknown and is likely secondary organic aerosol (SOA). Meat cooking and motor vehicles were the major sources of the resolved OC PM at the Fresno site. Size-resolved source apportionment deposition results were generated using a dosimetry model. Motor-vehicle OC deposition was greatest at the urban site and wood burning deposition was greater during the winter events. Health effects observed during the Fresno Summer sampling event may be due to the increased deposition of motor-vehicle-related PM$_(1.8) and/or PM$_(0.1), increased deposition of PM$_(1.8) dust/soil, increased deposition of unknown OC PM$_(1.8), and/or increased deposition of PM$_(0.1) motor oil. Differences in deposition patterns should provide useful information for inhalation exposure studies utilizing different sites and different seasons in the San Joaquin Valley.