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EVALUATION OF SECONDARY ORGANIC AEROSOL FORMATION IN WINTER. (R823514)
Citation:
Strader, R., F. Lurmann, AND S. N. Pandis. EVALUATION OF SECONDARY ORGANIC AEROSOL FORMATION IN WINTER. (R823514). ATMOSPHERIC ENVIRONMENT. American Chemical Society, Washington, DC, (1999).
Description:
Three different methods are used to predict secondary organic aerosol (SOA)
concentrations in the San Joaquin Valley of California during the winter of 1995-1996 [Integrated
Monitoring Study, (IMS95)]. The first of these methods estimates SOA by using elemental carbon as
a tracer of primary organic carbon. The second method relies on a Lagrangian trajectory model that
simulates the formation, transport, and deposition of secondary organic aerosol. The model includes a
recently developed gas-particle partitioning mechanism. Results from both methods are in good
agreement with the chemical speciation of organic aerosol during IMS95 and suggest that most of the
OC measured during IMS95 is of primary origin. Under suitable conditions (clear skies, low winds,
low mixing heights) as much as 15-20 mu g C m(-3) of SOA can be produced, mainly due to
oxidation of aromatics. The low mixing heights observed during the winter in the area allow
accumulation of SOA precursors and the acceleration of SOA formation. Clouds and fog slow down
the production of secondary compounds, reducing their concentrations by a factor of two or three
from the above maximum levels. In addition, it appears that there is significant diurnal variation of
SOA concentration. A strong dependence of SOA concentrations on temperature is observed, along
with the existence of an optimal temperature for SOA formation. (C) 1999 Elsevier Science Ltd. All
rights reserved. (23 References)