AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Secondary Organic Aerosol Formation from the Emissions of Soil and Leaf Litter Collected in a Temperate Coniferous Forest
CELIA FAIOLA, Graham VanderSchelden, Miao Wen, Doug Cobos, B. Thomas Jobson, Timothy M. VanReken, Washington State University
Abstract Number: 432 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract In the United States, emissions of volatile organic compounds (VOCs) from natural sources are known to exceed all anthropogenic sources combined. VOCs participate in oxidative chemistry in the atmosphere and impact the concentrations of ozone and particulate material. The formation of secondary organic aerosol (SOA) is particularly complex and is frequently underestimated using state-of-the-art modeling techniques. We present findings that suggest emissions of important SOA precursors from soil and leaf litter are higher than current inventories would suggest.
Soil and leaf litter samples were collected at Big Meadow Creek from the University of Idaho Experimental Forest. The dominant tree species in this area of the forest are ponderosa and white pine, douglas fir, western larch, and cottonwood. Samples were transported to the laboratory and housed within a 0.3 cubic meter Teflon dynamic chamber where VOC emissions were continuously monitored. To generate aerosol, soil and leaf litter emissions were pumped into a 7 cubic meter Teflon aerosol growth chamber where they were oxidized with ozone in the absence of light. The evolution of gas-phase species and particle characteristics were monitored over the following eight hours. Gas-phase species were measured within the soil chamber and aerosol growth chamber with a GC-MS-FID and a PTR-MS. Particle size distribution, chemical composition, and hygroscopic properties were measured in the aerosol growth chamber with a SMPS, HR-ToF-AMS, and CCNc respectively. Monoterpenes dominated the emission profile with emission rates up to 283 micrograms carbon per meter squared per hour. These emission rates are higher than those presented previously from summertime measurements, but are consistent with other results from springtime measurements in Finland. The dominant monoterpenes emitted were beta-pinene, alpha-pinene, and delta-3-carene in descending order. SOA yields and compositional profiles have also been evaluated and compared to other SOA derived from biogenic precursors.