Collaborative Research (UCR, OSU and ASU): Combined Fe-S Stable Isotopes in Modern Anoxic Environments and the Effect of Fe versus S Limitation

摘要塞弗曼，安巴尔，麦克马纳斯（0551716，0551732，0551605）学术价值：铁和硫的地球化学循环是紧密耦合的，它们的综合影响影响了全球碳和氧循环的演变，以及地质时期海洋的质子平衡。我们的初步数据表明，溶解和颗粒物种的铁同位素组成明确地反映了它们在现代水环境中的沉积条件。这项研究确定了这些周期的同位素表达，特别是与铁和硫在缺氧的水环境中的主要来源和汇。 要解决的具体问题是：（1）铁和硫的相对有效性如何影响其循环的同位素表达和（2）底栖铁再循环的好氧大陆架影响缺氧盆地沉积物中的铁同位素组成。 将分析来自两个现代缺氧湖泊环境的样品，这些样品具有对比鲜明的硫酸盐水平（黑海硫酸盐富集，坦噶尼喀湖硫酸盐贫乏）。 这项工作利用了正在进行的NSF资助的研究，所有样品都带有丰富的辅助数据集，提供了有关S同位素组成，Fe形态和一般沉积物成岩参数的重要信息。 拟议的工作将提供必要的信息，我们的解释铁循环在现代和古代海洋以及地球大气的演变和现代大气-海洋系统的氧化还原平衡。Fe和S将通过连续浸出从沉积物样品中提取。 将使用多收集器ICP-MS或同位素比质谱法测量Fe和S同位素。 标准湿化学将用于确定相关孔隙沃茨和矿物沥滤物中的Fe和S形态。更广泛的影响：这项工作为三个州的研究机构提供资金：加州，俄勒冈州和亚利桑那州，并涉及与德国和土耳其科学家的国际合作。 该研究支持一名年轻的女性首席研究员和一名研究生，后者将花时间在合作机构学习分析技术。 它还将允许主要研究者和她的学生参与非洲的实地项目。 美国和非洲的本科生将参与并指导古气候研究。

ABSTRACT Severmann, Anbar, McManus (0551716, 0551732, 0551605)Intellectual merit: The biogeochemical cycles of iron and sulfur are closely coupled, and their combined influence impacts the evolution of the global carbon and oxygen cycles as well as the ocean's proton balance over geologic time. Our preliminary data show that Fe isotope compositions of dissolved and particulate species unambiguously reflect their depositional conditions in modern aqueous environments. This research determines the isotopic expressions of these cycles as specifically linked to the primary sources and sinks of Fe and S in oxygen-deficient aqueous settings. Specific questions to be addressed are: (1) how does the relative availability of Fe and S influence the isotopic expression of their cycling and (2) does benthic Fe recycling on oxic continental shelves influence the Fe isotope composition within anoxic basin sediments. Samples from two modern anoxic lake environments with contrasting sulfate levels will be analyzed (the Black Sea sulfate enriched, and Lake Tanganyika sulfate poor). This work leverages off on-going NSF-funded studies and all samples come with rich ancillary data sets, providing essential information regarding S isotope compositions, Fe speciation and general sediment diagenetic parameters. The proposed work will provide information essential to our interpretation of the Fe cycle in both the modern and ancient ocean as well as the evolution of the Earth's atmosphere and the redox balance of the modern atmosphere-ocean system. Fe and S will be extracted from sediment samples by sequential leaching. Fe and S isotopes will be measured using a multi-collector ICP-MS or isotope ratio mass spectrometry. Standard wet chemistry will be used to determine Fe and S speciation in the associated pore waters and mineral leachates.Broader impacts: This work funds investigators at institutions in three states: California, Oregon, and Arizona and involved international collaborations with scientists in Germany and Turkey. The research supports a young, female principal investigator and a graduate student, the latter who will spend time learning analytical techniques in the collaborating institutions. It will also allow participation of the lead PI and her student to participate in the field program in Africa. US, as well as African undergraduates will be involved and mentored in paleoclimate research.