Career: Geochemistry of Redox-Sensitive Elements and Osmium and Uranium Isotopes in Large Pristine Rivers

职业：大型原始河流中氧化还原敏感元素以及锇和铀同位素的地球化学

• 批准号: 0134966
• 负责人: Youngsook Huh
• 金额: $ 37.5万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-15 至 2008-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0134966&HistoricalAwards=false
• 关键词: Career; Geochemistry; Redox; Sensitive; Elements

0134966HudContinental weathering is an important component of global geochemical cycles and is one of the most significant determinants of the atmospheric CO2 levels, and hence climate, on geologic time scales. Weathering of organic carbon is an important source of CO2; weathering of silicates a sink. The long-term goal of the PI's research is to understand the mechanisms and magnitudes of continental weathering in various pristine environments at present and to then project the results into the geologic past using suitable proxies. In this endeavor, characterizing the behavior of different chemical elements as a function of weathering environment is important. The PI proposes to study weathering of organic carbon rich reducing sediments as manifested in large pristine rivers. This proposal describes an integrative approach using redox-sensitive, oxyanion-forming elements (Re, Mo, V, U) and the Os isotopic system (187Os/188Os) intimately related to them. These elements are enriched in reducing sediments and are released as soluble oxyanions when they undergo fast oxidative weathering. The proposed research activities consist of three parts: field work, instrumental analyses and data interpretation. Field work will be carried out in western China, eastern Tibet, and northern Vietnam, areas affected by the Himalayan collision but whose fluvial geochemistry is poorly understood. This will be a continuation of the successful collaboration with scientists in China and Vietnam. A graduate student at Northwestern University and visiting scholars from China/Vietnam will be involved in all three activities. At undergraduate students level, this research will be integrated into the Analytical Methods in Geochemistry course that the PI is developing to strengthen the interdisciplinary Environmental Science Program at Northwestern University.This work will provide fundamental understanding of the behavior of redox-sensitive elements and Os isotopes, which is in turn important in deciphering the paleo-environments of the Earth. Additional benefit is documenting the present weathering regime of the Upper Yangtze, which is important for the Chinese scientists in their attempt to monitor the effect of the Three Gorges Dam and erosion of top soil that is becoming a serious problem. Also, a clear comparison can be made between the undeveloped headwaters and the agriculturally impacted lower reaches of the Chinese and Vietnamese rivers.

[01:49 . 66]大陆风化作用是全球地球化学循环的重要组成部分，也是地质年代尺度上大气二氧化碳水平和气候的最重要决定因素之一。有机碳的风化作用是CO2的重要来源；硅酸盐的风化作用。PI研究的长期目标是了解目前各种原始环境下大陆风化的机制和程度，然后使用合适的代用物将结果预测到地质过去。在这一努力中，表征不同化学元素的行为作为风化环境的功能是很重要的。PI建议研究大型原始河流中富有机碳还原沉积物的风化作用。本文介绍了一种利用氧化还原敏感的氧阴离子形成元素（Re, Mo， V， U）和与其密切相关的Os同位素系统（187Os/188Os）的综合方法。这些元素在还原性沉积物中富集，并在经历快速氧化风化时以可溶性氧离子的形式释放出来。拟议的研究活动包括三部分：实地工作、仪器分析和数据解释。这将是与中国和越南科学家成功合作的延续。美国西北大学的一名研究生和来自中国/越南的访问学者将参与这三项活动。在本科生阶段，这项研究将被整合到PI正在开发的地球化学分析方法课程中，以加强西北大学跨学科的环境科学项目。这项工作将为氧化还原敏感元素和Os同位素的行为提供基本的理解，这反过来对破译地球的古环境很重要。另外一个好处是记录了长江上游目前的风化情况，这对中国科学家监测三峡大坝和表层土壤侵蚀的影响非常重要，表层土壤侵蚀正在成为一个严重的问题。此外，中国和越南河流未开发的源头与受农业影响的下游之间也可以进行清晰的比较。