This project is a systematic field study of atmospheric sulfur chemistry in the antarctic troposphere. The specific objective is to obtain a comprehensive data base for estimating the potential impact of dimethylsulfide (DMS) emissions on the climate of Antarctica, and by extension, the global climate. Field measurements will be conducted at Palmer Station during two austral summer months in the 1993-94 and the 1994-95 season. It is known that approximately 80 to 90 percent of the aerosol mass deposited to the antarctic ice sheet consists of fine par- ticles of non-sea salt sulfate. These particles are though to be formed by gas-to-particle conversion involving biogenic sulfur gases emitted from the Southern Ocean. Some antarctic phytoplankton species emit large quantities of DMS which is subsequently oxidized by the hydroxyl radical, forming sulfuric acid as one of the end products. Sulfuric acid in the atmosphere may condense to form nanometer droplets or become condensed on pre- existing aerosol particles; these phase transitions form non-sea salt sulfate which is then precipitated to the ice sheet. These processes will be traced by the direct measurement of twenty sulfur-containing species as well as the aerosol and condensation nuclei size distribution. Recently developed highly sensitive techniques will be applied to the antarctic troposphere for the first time. The resulting information will be used to assess the relative importance of individual chemical reaction pathways which will contribute to the better understanding of the marine biogenic sulfur record in antarctic ice cores with respect to past climate changes. It will also provide a model data base for estimating the sensitivity of the present climate of Antarctica to volcanic or anthropogenic sulfur pollution and its effect on the ultraviolet radiation regime.
