Collaborative Research: Investigation Atomospheric Chemisty and Dynamics Through Oxygen and Sulfur Isotopes in Volcanic Sulfate from South Pole Ice Cores

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This award supports a collaborative study between South Dakota State University (SDSU) and University of California, San Diego (UCSD) to investigate the oxygen and sulfur isotope composition of sulfates from a number of large volcanic eruptions in the past 1000 years. The project aims to drill a number of shallow ice cores at South Pole and return them to SDSU and UCSD lab for chemical and isotope analysis. Preliminary results from measurements of isotopes in sulfate samples from several volcanic eruptions in Antarctic snow and ice indicate that isotopic composition of volcanic sulfate contains abundant valuable information on atmospheric chemical and dynamic processes that have not been previously investigated. One tentative conclusion is that mass-independently fractionated sulfur isotopes reveal that atmospheric photolysis of sulfur compounds occurs at longer UV wavelengths than those in the Archean atmosphere, possibly reflecting the atmospheric ozone and/or oxygen concentration. This suggests that isotopic composition of atmospheric sulfate may be used to understand the role of UV radiation in sulfur dioxide conversion in the atmosphere and to track the evolution (i.e., oxygenation) of the atmosphere and the origin of life on Earth. Other major research objectives include understanding what impact massive volcanic eruptions have on the oxidative capacity of the atmosphere, what oxidants and mechanisms are involved in the oxidation or conversion of volcanic sulfur dioxide to sulfate in the stratosphere and what isotopic criteria may be used to differentiate ice core signals of stratospheric eruptions from those of tropospheric eruptions. By providing educational and research opportunities to graduate and undergraduate students at both SDSU and UCSD, the proposed project will promote the integration of research and education and contribute to human resource development in science and engineering. The project will contribute to a proposed REU chemistry site program at SDSU. This collaboration will utilize the complementary strengths of both labs and promote exchange between the two institutions. International collaboration will enhance scientific cooperation between France and US.