Ann Marie Carlton (EPA) - To What Extent Can Biogenic SOA be Controlled?
Date Time Location
November 30th, 2009 12:00pm-1:00pm 54-915
Ann Marie Carlton
EPA
Title: "To What Extent Can Biogenic SOA be Controlled?"
Host: Eunjee Lee

Abstract:
Anthropogenic pollution facilitates conversion of naturally emitted
volatile organic compounds (VOCs) to the particle phase, enhancing
biogenic secondary organic aerosol (SOA) in the atmosphere. ‘Biogenic’
SOA is a product of natural precursor VOCs as well as anthropogenic
constituents. Anthropogenic pollution increases concentrations of
oxidants (O3, OH, NO3) that convert biogenic VOCs to semi-volatile,
condensable, SOA-contributing species. Furthermore, increases in
concentrations of primary organic matter facilitate condensation of
semi-volatile biogenic species to the particle phase. Therefore, a
portion of biogenic SOA can be attributed to anthropogenic emissions and
may be controllable. Direct measurement of this component is not
possible, but it can be estimated through modeling.

To test the contribution of anthropogenic pollution to biogenic SOA, CMAQ
model simulations were conducted for the continental U.S. (August 18 –
September 4) using a recently developed SOA module that includes several
biogenic SOA precursors: isoprene, sesquiterpenes, monoterpenes. Biogenic
SOA formation pathways include oxidation of volatile species to
semi-voltaile products followed by gas-to-particle partitioning,
oligomerization and in-cloud processes. CMAQ simulations were conducted
with and without anthropogenic emissions. The relative contributions of
individual pollution classes (i.e., NOx, VOCs, NH3, SO2 and primary
organic particulate matter) were also evaluated by removing the individual
components from the emissions, one at a time. Model results demonstrate a
strong influence of anthropogenic pollution on predicted ‘biogenic’ SOA
concentrations. In these simulations, approximately 40% of biogenic SOA
in the eastern U.S. can be controlled. Total biogenic SOA was most
sensitive to primary organic particulate matter emissions, suggesting
reductions in PM emissions could reduce biogenic SOA by ~20%. Individual
biogenic SOA species exhibit different responses to anthropogenic emission
reductions. Cloud-produced SOA, which has biogenic and anthropogenic VOC
precursors was most sensitive to NOx reductions.