CAREER: The Role of Sulfur in Regulating the Marine Carbon Cycle: Implications for Understanding Oceanic Anoxic Events

职业：硫在调节海洋碳循环中的作用：对理解海洋缺氧事件的影响

• 批准号: 0955969
• 负责人: Matthew Hurtgen
• 金额: $ 51.19万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-15 至 2016-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0955969&HistoricalAwards=false
• 关键词: CAREER; Role; Sulfur; Regulating; Marine

Intellectual Merit: Oceanic anoxic events (OAE) record significant increases in organic carbon burial and are marked by positive excursions in both marine carbonate and organic carbon (C). While it is widely held that these events were driven by enhanced primary production within surface waters, the details underpinning the initiation, maintenance and termination of OAEs remain equivocal. This work will reveal the potential of sulfur (S) isotope studies to illuminate the role of changing sulfate concentrations on phosphate (PO4) regeneration in marine sediments and will have far-reaching implications for understanding the behavior of the C cycle, and therefore climate, especially in the deep time record. This is because marine sulfate levels have been low for much of Earth history. The objective of this proposal is to investigate the role sulfur plays in regulating the marine carbon cycle in low sulfate oceans. The following hypothesis will be tested: given an average background of low marine sulfate concentrations, an increase in seawater sulfate levels may trigger widespread oceanic anoxia by facilitating enhanced phosphorus (P) recycling and thus higher primary production within marine surface waters. Because seawater sulfate concentrations have been low for most of Earth?s history, substantial fluctuations in sulfate levels in the past may have played a key role in regulating C cycling in ancient oceans. In order to test this hypothesis, this proposal details a study with three fundamental themes, each of which will be integrated with an educational outreach effort developed through the Office of STEM Education Partnerships (OSEP) in the School of Education and Social Policy at Northwestern University. The themes include: (1) S isotope systematics and the link between fluctuating sulfate levels and P recycling in a low sulfate, permanently anoxic lake (Lake McCarrons, MN), (2) the S isotope composition of seawater sulfate, sedimentary pyrite and difference between the two phases (Ä34S) before, during and after two oceanic anoxic events?OAE1a in the Early Cretaceous and the Frasnian-Famennian event in the Late Devonian, and (3) reservoir dependent mass balance modeling using S isotopes. The results from this project will improve the community?s understanding of S and P cycling in low sulfate systems, establish Ä34Ssulfate-pyrite for two time periods marked by widespread anoxia (the Early Cretaceous and the Late Devonian), and help to ascertain the complex set of feedbacks that link ocean redox and the geochemical cycles of C, S, P, and Fe in the low sulfate oceans of Earth?s past.Broader Impacts: This project will provide training to two graduate students in field research techniques and analytical isotope geochemistry and make contributions to understanding controls on biogeochemical cycles of C, S, P and Fe and their relationship to the redox state of the Earth system. Impacts of this project extend beyond the scientific community via an outreach effort to public high schools. The overall goal of the outreach effort is to bring the excitement and challenge of doing real science to high school students. This proposal requests funds to recruit a local high school science teacher to participate in research each summer. This teacher will collaborate to develop laboratory activities to provide high school students with research experiences through the NSF-funded iLab Network (ilabcentral.org), which allows students and educators to use remote experimental apparatus to carry out experiments via the Web. Once the iLab experiments have been tested, through development with the initial high school and then with OSEP partner schools in the area, they will be made available to any high school teacher with a web browser. To address the problem of underrepresented groups in Earth Science, a partnership has been initiated with Project EXCITE, a program that links Northwestern?s Center for Talent Development with local schools to identify scientifically inclined minority students and support their acquisition of math and science skills through high school. Saturday enrichment sessions with Project EXCITE students and their parents are ongoing, focusing on key Earth science concepts (earthquakes, tsunamis, climate change) and career options in Earth and Planetary Sciences. This proposal seeks funds to support high school students from EXCITE as lab assistants to increase awareness of opportunities in Earth science for local students and their families.

知识价值：海洋缺氧事件（OAE）记录了有机碳埋藏的显著增加，并以海洋碳酸盐和有机碳(C)的正偏移为标志。虽然人们普遍认为，这些事件是由地表水内初级生产的增加所驱动的，但支撑oae启动、维持和终止的细节仍然模棱两可。这项工作将揭示硫(S)同位素研究的潜力，以阐明硫酸盐浓度变化对海洋沉积物中磷酸盐（PO4）再生的作用，并将对理解C循环的行为，从而对气候，特别是在深时间记录中的气候行为产生深远的影响。这是因为在地球历史的大部分时间里，海洋硫酸盐含量一直很低。本提案的目的是研究硫在低硫酸盐海洋中调节海洋碳循环的作用。将检验以下假设：在海洋硫酸盐浓度较低的平均背景下，海水硫酸盐水平的增加可能会促进磷(P)的循环，从而提高海洋表层水中的初级产量，从而引发广泛的海洋缺氧。因为地球大部分地区的海水硫酸盐浓度都很低？从历史上看，过去硫酸盐水平的大幅波动可能在调节古代海洋中的碳循环中发挥了关键作用。为了验证这一假设，本提案详细介绍了一项有三个基本主题的研究，每个主题都将与西北大学教育与社会政策学院STEM教育伙伴关系办公室（OSEP）开发的教育推广工作相结合。主题包括：(1)低硫酸盐永久性缺氧湖泊（lake McCarrons， MN）中硫酸盐含量波动与磷循环之间的联系及S同位素系统；(2)两次海洋缺氧事件发生前、期间和之后，海水硫酸盐、沉积黄铁矿的S同位素组成及其两相差异（Ä34S）。早白垩世的OAE1a和晚泥盆世的frasian - famenian事件，以及(3)利用S同位素建立储层依赖的质量平衡模型。这个项目的结果会改善社区吗？通过对低硫酸盐体系中s和P循环的理解，建立了以广泛缺氧为标志的两个时期（早白垩世和晚泥盆世）Ä34Ssulfate-pyrite，并有助于确定地球低硫酸盐海洋中海洋氧化还原与C、s、P和Fe的地球化学循环之间的复杂反馈集。年代的过去。更广泛的影响：该项目将为两名研究生提供实地研究技术和分析同位素地球化学方面的培训，并为理解C、S、P和Fe的生物地球化学循环控制及其与地球系统氧化还原状态的关系做出贡献。这个项目的影响通过向公立高中的推广而超越了科学界。推广工作的总体目标是给高中生带来做真正科学的兴奋和挑战。该提案要求基金每年夏天招募一名当地高中科学教师参与研究。该教师将合作开发实验室活动，通过nsf资助的iLab网络（ilabcentral.org）为高中生提供研究经验，该网络允许学生和教育工作者使用远程实验设备通过网络进行实验。一旦iLab实验通过与最初的高中和该地区的OSEP合作学校的开发进行测试，它们将通过网络浏览器提供给任何高中教师。为了解决地球科学领域代表性不足的群体问题，我们与EXCITE项目建立了合作关系。美国的人才发展中心（Center for Talent Development）与当地学校合作，识别有科学倾向的少数民族学生，并支持他们在高中阶段获得数学和科学技能。与“激发计划”的学生及其家长一起参加的周六强化课程正在进行中，重点是地球科学的关键概念（地震、海啸、气候变化）以及地球和行星科学的职业选择。该提案寻求资金支持来自EXCITE的高中生担任实验室助理，以提高当地学生及其家庭对地球科学机会的认识。