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

Severmann，Anbar，McManus(0551716,0551732,0551605)的学术价值：铁和硫的生物地球化学循环是紧密耦合的，它们的联合影响影响着全球碳氧循环的演化以及海洋在地质时代的质子平衡。我们的初步数据表明，溶解和颗粒态的铁同位素组成清楚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循环的同位素表达与缺氧水环境中铁和S的初级来源和汇有关。具体问题是：(1)Fe和S的相对有效性如何影响其循环的同位素表达；(2)氧化大陆架底栖铁循环是否影响缺氧盆地沉积物中的Fe同位素组成。来自两个硫酸盐水平不同的现代缺氧湖环境的样本将被分析(黑海硫酸盐丰富，坦噶尼喀湖硫酸盐贫乏)。这项工作利用了美国国家科学基金会正在进行的研究，所有样品都带有丰富的辅助数据集，提供了关于S同位素组成、铁的形态和一般沉积物成岩参数的基本信息。拟议的工作将为我们解释现代和古代海洋中的铁循环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提供必要的信息。采用顺序浸出的方法从沉积物样品中提取铁和S。铁和S的同位素将使用多收集器电感耦合等离子体质谱或同位素比质谱仪进行测量。将使用标准湿化学来确定相关孔隙水和矿物淋滤液中铁和S的形态。广泛影响：这项工作资助了加利福尼亚州、俄勒冈州和亚利桑那州三个州的研究机构的研究人员，并与德国和土耳其的科学家进行了国际合作。这项研究支持一名年轻的女性首席研究员和一名研究生，后者将花费时间在合作机构学习分析技术。它还将允许首席PI和她的学生参加非洲的实地项目。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.