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Investigation of Sulfur Chemistry in Antarctic Troposphere

Project Description
Research Objectives of the Investigation of Sulfur Chemistry in
Antarctic Troposphere (ISCAT):

During this four-year study at Amundsen-Scott South Pole
Station, we will examine the sulfur chemistry of the Antarctic
atmosphere. The study involves two field seasons, the first of
which was completed in 1998-1999. This field season (2000-2001)
will be the second and last for this project. The study, which
includes 10 principal and senior investigators at five
institutions, with seven additional contributing investigators,
has two broad-based goals: to improve substantially our current
understanding of the oxidation chemistry of bioorganic sulfur
in the polar environment, and to improve the climatic
interpretation of sulfur-based signals in Antarctic ice-core

The South Pole was selected because the atmospheric boundary
layer at this site presents a homogeneous and relatively simple
environment from which to unravel the photochemically driven
oxidation chemistry of dimethyl sulfide. Atmospheric sulfur
chemistry is an important component in climate change issues
because both naturally (i.e., from volcanic emissions and
oceanic phytoplankton production) and anthropogenically emitted
sulfur compounds form minute particles in the atmosphere--the
so-called aerosols--that reflect solar radiation, produce
atmospheric haze and acid rain, and affect ozone
depletion. Sulfate particles in the atmosphere may also act as
condensation nuclei for water vapor and enhance global
cloudiness. On the millennial time scale, the variability and
natural background level of atmospheric aerosols can be
reconstructed from the preserved paleorecords of sulfur
oxidation products in ice cores. It is necessary, however, to
understand how the physical and chemi! cal environment of the
oxidation process affects the relative concentrations of the
oxidation products that become buried in the ice. This study
requires simultaneous observations of a wide-ranging suite of
sulfur species, such as DMS and its oxidation products, sulfur
dioxide, dimethyl sulfoxide, dimethyl sulfone, methane sulfonic
acid, and sulfuric acid, as well as photochemically important
compounds such as carbon monoxide, nitrous oxide, water vapor,
and non-methane hydrocarbons.

Secondary objectives will be:

to examine interior Antarctic air samples for other significant
DMS oxidation products, such as sulfurous acid and methane
sulfonic acid; and to assess the local variation in hydroxyl and
perhydroxyl radicals, a measure of the oxidizing power of the
atmosphere. This study will provide, for the first time, a
quantitative picture of exactly which atmospheric sulfur
compounds are advected into the Antarctic interior and a
detailed picture of the sulfur chemistry that is active in the
Antarctic atmosphere.

Contact Information:

Dr. Douglas Davis, Principal Investigator

Georgia Institute of Technology
School of Earth and Atmospheric Sciences
221 Bobby Dodd Way
Atlanta, GA 30332-0340

Phone: 404-894-4008
Fax: 404-894-1993

For more information,
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[Summary provided by Raytheon]
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