Collaborative Research: Investigation Atomospheric Chemisty 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立大学（SDSU）和加州大学圣地亚哥分校（UCSD）之间的一项合作研究，该研究旨在调查过去1000年来许多大型火山喷发中硫酸盐的氧和硫同位素组成。该项目旨在在南极钻取一些浅层冰芯，并将它们送回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的同位素测量的初步结果表明，火山硫酸盐的同位素组成包含了大量关于大气化学和动力学过程的宝贵信息，这些信息以前没有被研究过。一个初步的结论是，与质量无关的硫同位素分异表明，大气中硫化合物的光解作用发生在比太古宙大气中的紫外线波长更长的波段，这可能反映了大气中臭氧和/或氧的浓度。这表明大气硫酸盐的同位素组成可以用来了解紫外线辐射在大气中二氧化硫转化中的作用，并跟踪大气的演化（即氧化）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喷发对大气氧化能力的影响，火山二氧化硫在平流层中氧化或转化为硫酸盐的氧化剂和机制，以及可用于区分平流层喷发和对流层喷发冰芯信号的同位素标准。通过为圣地亚哥州立大学和加州大学圣地亚哥分校的研究生和本科生提供教育和研究机会，拟议中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。该项目将为SDSU的REU化学基地计划做出贡献。此次合作将利用两所实验室的互补优势，促进两所机构之间的交流。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.