EAGER: Unraveling riverine sulfate using minor oxygen isotopes

在地质时间尺度上，涉及陆地表面矿物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数量。 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反应：矿物黄铁矿的氧化。 在过去的地质历史中，被氧化的黄铁矿数量的全球变化提供了地球碳和硫循环之间的关键联系，而这一历史的记录可能被海洋沉积物中的硫酸盐矿物保存下来。 研究人员将生成一个概念验证数据集，该数据集利用了可以从溶解和矿物硫酸盐中罕见且难以测量的稳定同位素17-氧中收集的信息。 这种新的方法将被应用到以前收集的和良好的特点，从一个主要的河流系统排水喜马拉雅山脉的水样。 这一试验数据集将提供关于控制溶解硫酸盐同位素组成的机制的重要信息，并将有助于揭示保存在海洋沉积物中的记录。该奖项还将为一名博士后研究员提供指导，该博士后研究员为该项目的设计和规划做出了贡献，并将为个人提供在研究小组中担任领导角色的机会。该奖项将资助探索一种新的替代物的潜力，该替代物基于黄铁矿氧化产生的硫酸盐中保存的次要氧稳定同位素（17-O）来量化黄铁矿氧化的地质速率。由于黄铁矿氧化既消耗氧气，又产生酸性，溶解碳酸盐岩并产生CO2，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CO2波动的作用。虽然黄铁矿氧化是地球的碳和硫循环之间的一个关键环节，17-O代理海洋硫酸盐的应用是有限的，我们通过河流系统的硫酸盐生成和翻译的理解。这项工作将开始，以缩小这一差距，产生一个概念验证的数据集，从一个主要的河流系统排水的喜马拉雅山脉，已经测量了溶解硫酸盐的34-S和18-O组成的良好特性的河流样本。研究人员将增加对这些样本中溶解硫酸盐的17 O成分的测量，以调查下游洪泛区硫酸盐的潜在来源和随后的再循环。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NSF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.