Collaborative Research: An Isotope MIF Study of Volcanic Events in Greenland Ice Cores

南达科他州立大学和加州大学圣地亚哥分校的这项合作研究将利用火山喷发产生的二氧化硫来研究大气氧化化学的机制。主要研究人员将：1)从格陵兰中部获得几个浅层冰芯；2)从过去600年已知的一些大型火山喷发中提取硫酸盐；3)测定火山硫酸盐中硫、氧同位素的质量无关分馏（MIF）；4)检验活性氧化中间体和光化学对二氧化硫氧化的假设；5)研究大气变量对冰芯火山信号的定量影响。目标是：1)更好地了解大气氧化的化学过程和大气动力学对冰芯火山信号的影响；2)建立一种新的机制来跟踪大气对环境干扰的敏感性，从而对人为影响模型具有重要意义。知识价值：氧化是大气中最基本的化学转化过程之一。它在全球生物地球化学循环和从大气中去除许多污染物化学物质方面起着至关重要的作用。从自然或人为来源引入的大量化学物质可改变大气的氧化能力，并影响大气环境的质量和功能。对大气氧化机制，特别是平流层氧化机制的了解非常有限，这妨碍了构建可靠模型来预测人为对大气环境影响的努力。首席研究人员最近发现，从南极冰芯中提取的火山硫酸盐的MIF同位素特征包含了关于大气氧化的新的有价值的信息，这些信息是通过其他方法无法获得的。有限的数据引起了大气建模者的注意，他们提出了替代光化学和/或氧化过程的建议。需要更多的同位素MIF数据来测试和鼓励由初步结果激发的新假设。在一个正在进行的项目中，他们将南极冰芯中火山硫酸盐的测量值添加到MIF数据集中。该项目将从北半球冰芯中获得第一个火山硫酸盐MIF数据。他们将利用双极火山硫酸盐MIF数据集：1)确定平流层氧化化学的全球均匀性；2)检验平流层SO3光解的假设；3)确定两次气候上重要的大型火山爆发的平流层或对流层性质和程度；4)建立并验证定量的mif -质量负荷关系，该关系可用于根据冰芯硫酸盐信号估计过去火山喷发的气溶胶影响。更广泛的影响：实现研究目标将有助于推进环境科学的前沿，特别是在气候变化和人类影响领域。通过为圣地亚哥州立大学和加州大学圣地亚哥分校的学生提供教育和研究机会，该项目将促进研究与教育的结合，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当前的REU化学现场计划做出贡献。

7ABSTRACTCole-DaiOPP-0612451ThiemensOPP-0612422This collaborative study between South Dakota State University and Universityof California, San Diego will investigate mechanisms of atmospheric oxidationchemistry using sulfur dioxide from volcanic eruptions. The Principal Investigators will: 1) obtain several shallow ice cores from central Greenland; 2) extract sulfate from a number of known large volcanic eruptions in the last 600 years; 3) measure the mass independent fractionation (MIF) of sulfur and oxygen isotopes in the volcanic sulfate; 4) test hypotheses of sulfur dioxide oxidation by active oxidation intermediates and by photochemistry; and 5) investigate the quantitative impact of atmospheric variables on ice core volcanic signals. The goals are to: 1) better understand the chemical processes of atmospheric oxidation and the effect of atmospheric dynamics on ice core volcanic signals, and 2) to establish a new mechanism to track the sensitivity of the atmosphere to environmental disturbance and hence, is of importance to anthropogenic impact models.Intellectual Merit: Oxidation is one of the basic chemical transformation processes in the atmosphere. It plays a critically important role in global biogeochemical cycles and in the removal of many pollutant chemicals from the atmosphere. Introduction of large amounts of chemical substances, from either natural or anthropogenic sources, can alter the atmosphere's oxidative abilities and affect the quality and functions of the atmospheric environment. Very limited knowledge of the mechanisms of atmospheric oxidation, particularly in the stratosphere, hampers the efforts to construct robust models to predict anthropogenic impact on the atmospheric environment. The Principal Investigators recently discovered that MIF isotopic signatures of volcanic sulfate extracted from Antarctica ice cores contain new and valuable information on atmospheric oxidation that is unavailable by other means. Limited data have attracted attention from atmospheric modelers with proposals of alternative photochemical and/or oxidation processes. More isotopic MIF data are needed both to test and to encourage new hypotheses spurred by preliminary results. In an on-going project, they added to the MIF dataset with measurements on volcanic sulfate from South Pole ice cores. This project will produce first volcanic sulfate MIF data from Northern Hemisphere ice cores. They will use the bi-polar volcanic sulfate MIF dataset to: 1) determine the global homogeneity of stratospheric oxidation chemistry, 2) test the hypothesis of stratospheric SO3 photolysis, 3) determine the stratospheric or tropospheric nature and degree of two climatologically important large volcanic eruptions; and 4) establish and verify a quantitative MIF-mass loading relationship that can be used to estimate aerosol impact of past volcanic eruptions from their ice core sulfate signals.Broader Impacts: Achieving the goals of the research will help advance the frontiers of environmental science, particularly in the areas of climate change and human impact. By providing educational and research opportunities to SDSU and UCSD students, the project will promote the integration of research with education and contribute to human resource development in science and engineering. The project will contribute to a current REU chemistry site program at SDSU.