EAGER: Unraveling riverine sulfate using minor oxygen isotopes

在地质年代尺度上，涉及地表矿物质的风化反应调节了地球大气中氧气和二氧化碳等重要气体的含量。该奖项资助的研究将探索一种新方法的潜力，以限制地球历史上的一种这样的反应：矿物黄铁矿的氧化。在过去的地质历史中，黄铁矿氧化量的全球变化为地球的碳和硫循环提供了关键的联系，而海洋沉积物中的硫酸盐矿物可能保存了这一历史的记录。研究人员将生成一个概念验证数据集，该数据集利用了从溶解和矿物硫酸盐中罕见且难以测量的稳定同位素17-氧中收集到的信息。这种新颖的方法将应用于以前收集和良好表征的水样从一个主要的河流系统排水喜马拉雅山脉。这一试验性数据集将提供有关控制溶解硫酸盐同位素组成的机制的重要信息，并将有助于解开保存在海洋沉积物中的记录。该奖项还将为为该项目的设计和规划做出贡献的博士后提供指导，并将为个人提供在研究小组中担任领导角色的机会。该奖项资助了对黄铁矿氧化产生的硫酸盐中保存的微量氧稳定同位素（17-O）的潜在量化黄铁矿氧化地质速率的新代理的探索。由于黄铁矿氧化既消耗氧气，又产生酸度，从而溶解碳酸盐岩并产生二氧化碳，因此有人认为黄铁矿氧化速率的变化可能起到了稳定大气中二氧化碳波动的作用。虽然黄铁矿氧化是地球碳和硫循环之间的关键环节，但由于我们对硫酸盐通过河流系统生成和转化的理解，17-O代物在海洋硫酸盐中的应用受到限制。这项工作将开始通过生成一个概念验证数据集来缩小这一差距，该数据集来自喜马拉雅山脉主要河流系统的特征良好的河流样本，该样本已经测量了溶解硫酸盐的34-S和18-O成分。研究人员将对这些样品中溶解硫酸盐的17O组成进行测量，以调查硫酸盐的潜在来源和随后在下游洪泛平原的再循环。河流17-O-硫酸盐数据集将为解释海洋硫酸盐记录中的17-O记录提供一个严格的框架。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Over geological timescales, weathering reactions involving minerals on the land surface have regulated the amounts of important gases such as oxygen and carbon dioxide in Earth's atmosphere. This award funds research that will explore the potential for a new method to provide constraints on one such reaction in Earth history: the oxidation of the mineral pyrite. Over the geological past, global variation in the amount of pyrite that has been oxidized provides a critical link between Earth's carbon and sulfur cycles, while a record of this history may be preserved by sulfate minerals in marine sediments. The researchers will generate a proof-of-concept data set that takes advantage of information that can be gathered from a rare and difficult-to-measure stable isotope in dissolved and mineral sulfate: 17-oxygen. This novel method will be applied to previously collected and well-characterized water samples from a major river system draining the Himalaya Range. This pilot data set will provide important information about the mechanisms that control the isotopic composition of dissolved sulfate and will help to unravel the record that is preserved in marine sediments. The award will also provide mentoring for a postdoctoral fellow who has contributed to the design and planning of this project and will provide the individual with opportunities for leadership roles within the research group.This award funds the exploration of the potential for a new proxy to quantify geological rates of pyrite oxidation, based on the minor oxygen stable isotope (17-O) preserved in sulfate produced by pyrite oxidation. Because pyrite oxidation both consumes oxygen and generates acidity that dissolves carbonate rocks and produces CO2, it has been suggested that changes in pyrite oxidation rates may have acted to stabilize fluctuations in atmospheric CO2. Although pyrite oxidation is a critical link between Earth's carbon and sulfur cycles, the application of a 17-O proxy in marine sulfate is limited by our understanding of sulfate generation and translation through fluvial systems. This work would begin to narrow this gap by generating a proof-of-concept data set from well-characterized river samples from a major river system draining the Himalaya Range that has already been measured for 34-S and 18-O composition of dissolved sulfate. The researchers will add measurements of the 17O composition of dissolved sulfate from these samples to investigate the potential sources and subsequent recycling of sulfate in downstream floodplains. The riverine 17-O-sulfate data set will provide a rigid framework with which to interpret 17-O records in the marine sulfate record.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.