Collaborative Research: Investigating Atmospheric Chemistry and Dynamics through Oxygen and Sulfur Isotopes in Volcanic Sulfate from South Pole Ice Cores

该奖项支持南达科他州州立大学（SDSU）和加州大学圣地亚哥分校（UCSD）之间的合作研究，以调查过去1000年来许多大型火山爆发的硫酸盐的氧和硫同位素组成。 该项目的目的是在南极钻取一些浅冰芯，并将其送回SDSU和UCSD实验室进行化学和同位素分析。对南极冰雪中几次火山喷发的硫酸盐样品进行同位素测定的初步结果表明，火山硫酸盐的同位素组成包含了丰富而有价值的大气化学和动力学过程的信息。 一个初步的结论是，质量无关分馏硫同位素显示，大气中的硫化合物的光解发生在较长的紫外线波长比那些在太古代大气中，可能反映了大气中的臭氧和/或氧气浓度。这表明，大气硫酸盐的同位素组成可用于了解紫外线辐射在大气中二氧化硫转化中的作用，并跟踪其演变（即，大气层的氧化作用和地球上生命的起源。其他主要研究目标包括了解大规模火山爆发对大气氧化能力的影响，在平流层中火山二氧化硫氧化或转化为硫酸盐的过程中涉及哪些氧化剂和机制，以及可以使用哪些同位素标准来区分平流层爆发的冰芯信号和对流层爆发的冰芯信号。 通过为SDSU和UCSD的研究生和本科生提供教育和研究机会，拟议的项目将促进研究和教育的整合，并为科学和工程领域的人力资源开发做出贡献。该项目将有助于在SDSU拟议的REU化学网站计划。 这种合作将利用两个实验室的互补优势，促进两个机构之间的交流。 国际合作将加强法国和美国之间的科学合作。

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.