Sulfur isotope studies of sulfide oxidation

硫是地球海洋中常见的氧化活性元素，通过各种化学和生物过程进行循环。它在海水中最常见的形式是硫酸盐离子，这也是它最容易被氧化的形式。在海洋沉积物和深盆地的某些地区，这种硫酸盐被还原为硫化物。这一反应是由单细胞原核生物的代谢活动驱动的，占沉积有机碳总量的50%，这些有机碳被再氧化为碳酸盐/碳酸氢盐/碳酸/二氧化碳。大多数（~80-95%）的硫化物通过生物和非生物过程被再氧化。剩余的硫化物是固定的，主要通过与铁反应形成硫化物矿物黄铁矿，产生一个埋藏的还原硫储层，平衡了今天近30%的长期氧气产量。这笔拨款支持了一项与海水中硫化物氧化的非生物途径相关的速率和同位素特征的研究。生物和非生物途径产生的硫化合物的同位素特征是不同的，在表征良好的反应速率背景下校准这些同位素效应可用于追踪现代和古代环境中的氧化途径。这些信息将提供基本数据，用于校准描述碳埋藏和长期氧气生产的地球化学模型，并解开海洋环境中生物和非生物氧化过程的分布。这项资助还支持一名博士生，并包括制定一个项目的计划，以帮助当地一级小学的教师和学生发展他们的STEM项目。

Sulfur is a common redox-active element in Earth's oceans that is cycled by a variety of chemical and biological processes. Its most common form in seawater is as the sulfate ion, which is also its most oxidized form. In marine sediments and also in some parts of deep basins this sulfate is reduced to sulfide. This reaction is driven by the metabolic activity of single-celled prokaryotes and accounts for as much as 50% of the total sedimentary organic carbon that is reoxidized to carbonate/bicarbonate/carbonic acid/carbon dioxide. A majority (~80-95%) of sulfide produced this way is reoxidized by biological and abiological processes. The remaining sulfide is fixed, primarily by reaction with iron to form the sulfide mineral pyrite, generating a buried reservoir of reduced sulfur that balances almost 30% of the long-term oxygen production today. This grant supports a study of the rates and isotopic signatures associated with the abiological pathways of sulfide oxidation in seawater. The isotopic signatures in sulfur compounds produced by biological and abiological pathways are different, and calibrations of these isotope effects in the context of well-characterized reaction rates can be used to trace oxidation pathways in modern and ancient environments. This information will provide fundamental data that will be used to calibrate geochemical models that describe carbon burial and a long term oxygen production and also to disentangle the distribution of biological and abiological oxidation processes in marine environments. This grant also supports a Ph.D. student and includes plans to develop a program to assist teachers and students at local Title I elementary school with the development of their STEM program.