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7ABSTRACTCole-DaiOPP-0612451ThiemensOPP-0612422This合作研究将研究利用火山喷发产生的二氧化硫进行大气氧化化学的机制。首席调查人员将：1)从格陵兰岛中部获取几个浅层冰芯；2)从过去600年来已知的几次大型火山喷发中提取硫酸盐；3)测量火山硫酸盐中硫和氧同位素的质量独立分馏(MIF)；4)测试二氧化硫通过活性氧化中间体和光化学氧化的假说；以及5)调查大气变量对冰芯火山信号的定量影响。其目的是：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。它在全球生物地球化学循环和从大气中清除许多污染物化学物质方面发挥着至关重要的作用。来自自然或人为来源的大量化学物质的引入会改变大气的氧化能力，影响大气环境的质量和功能。对大气氧化机制的了解非常有限，特别是在平流层，这阻碍了建立可靠的模型来预测对大气环境的人为影响的努力。首席调查人员最近发现，从南极洲冰芯提取的火山硫酸盐的MIF同位素特征包含了其他方式无法获得的有关大气氧化的新的宝贵信息。有限的数据引起了大气模型者的注意，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数据来检验和鼓励由初步结果刺激的新假说。在一个正在进行的项目中，他们将南极冰芯的火山硫酸盐测量数据添加到MIF数据集。该项目将从北半球冰芯产生第一个火山硫酸盐MIF数据。他们将使用两极火山硫酸盐MIF数据集：1)确定平流层氧化化学的全球均质性，2)测试平流层SO3光解的假说，3)确定两次具有气候重要性的大型火山喷发的平流层或对流层性质和程度；以及4)建立和验证定量的MIF-质量负载关系，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。通过为南加州大学和加州大学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。该项目将有助于SDSU目前的REU化学现场计划。

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.