Multiple Sulfur Isotope Fractionations during Thermal Decomposition of and Thermochemical Sulfate Reduction by Natural Organic Compounds

天然有机化合物热分解和热化学硫酸还原过程中的多种硫同位素分馏

• 批准号: 1024550
• 负责人: Hiroshi Ohmoto
• 金额: $ 22.27万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1024550&HistoricalAwards=false
• 关键词: Multiple; Sulfur; Isotope; Fractionations; during

Intellectual merit: Anomalous isotope fractionations of sulfur (AIF-S) signatures preserved in pre-2.4 Ga sedimentary rocks have been used to drive the debate about when the Earth first had an oxygenated atmosphere. The mechanism for these sulfur isotope anomalies has been postulated to be produced by UV photolysis of volcanic SO2 gas in an anoxic atmosphere. Recent investigators, however, have recognized that the UV photolysis of SO2 by a broadband UV lamp, which closely simulates the UV spectra of sunlight, does not produce many of the AIF-S signatures in natural samples. The PI and colleagues reported the presence of distinct AIF-S signatures in the H2S and Cr-reducible sulfur species (probably disulfide) that were generated from relatively high temperature (150-200°C) reactions between crystals of amino acids and sodium sulfate in the presence of H2O, and suggested that thermochemical sulfate reduction (TSR) by organic matter in sediments might have produced some of the AIF-S signatures in pre-2.4 Ga sedimentary rocks (Watanabe et al., 2009). This discovery is significant, because, until this study, UV photolysis of SO2 was the only known cause for AIF-S. The TSR model was criticized by many researchers who claimed the process was not applicable to natural systems, in which the organic compounds are complex. Research proposed in this proposal will systematically investigate: (i) the multiple sulfur isotopic characteristics of the gaseous, liquid and solid products (e.g., H2S, Cr-reductive S, organic S compounds) and (ii) chemical characteristics (e.g., C/H/S/N ratios and compound ratios) of heavy hydrocarbon (oil) and light hydrocarbon (gas) that were generated during (a) thermal decomposition of, and (b) TSR by, the remnants of cyanobacteria and immature kerogen from the Eocene Green River Formation.The results would provide insight into (a) why AIF-S signatures are observed in both organic-rich, and some organic-poor rocks (e.g., BIFs and carbonates), (b) why AIF-S apparently disappeared in younger rocks; and (3) how the AIF-S record in sedimentary rocks can be linked to the environmental, chemical, and biological evolution of early Earth.Broader Impacts: The proposed project will a graduate student as a part of his Ph.D. thesis research and two undergraduate students (one per year) as a research assistants. The PI plans to participate in the WISE program: Women in the Sciences and Engineering Institute with a graduate researcher. Future students and young scientists will benefit from the new data and ideas generated from this project.

智力优点：在2.4 GA前岩石中保存的硫（AIF-S）特征的异常同位素分馏已被用于推动有关地球何时首次具有氧化气氛的争论。这些硫同位素异常的机制已被认为是通过在缺氧气氛中对火山SO2气体的紫外线光解产生的。然而，最近的研究人员已经认识到，宽带紫外线灯对SO2的紫外线光解（密切模拟阳光的紫外线光谱）并未在天然样品中产生许多AIF-S特征。 The PI and colleagues reported the presence of distinct AIF-S signatures in the H2S and Cr-reducible sulfur species (probably disulfide) that were generated from relatively high temperature (150-200°C) reactions between crystals of amino acids and sodium sulfate in the presence of H2O, and suggested that thermochemical sulfate reduction (TSR) by organic matter in sediments might have produced some of the AIF-S签名在2.4 GA前沉积岩石中（Watanabe等，2009）。这一发现很重要，因为在这项研究之前，SO2的紫外线光解是AIF-S的唯一已知原因。 TSR模型对许多研究人员来说至关重要，他们声称该过程不适用于自然系统，其中有机化合物很复杂。该提议中提出的研究将系统地研究：（i）气体，液体和固体产物的多种硫同位素特性（例如H2S，H2S，CR还原S，有机S化合物）和（ii）化学特性（例如C/H/S/N的均值（例如）和较高的基于水碳（油）的型号（例如，油）（油）的（油）型（机油）（油）（机油）的混合物（油）（机油）。 of和（b）TSR，由始新世绿河形成中的蓝细菌和未成熟的角膜菌的残留物。结果将提供（a）为何在有机富含有机的有机岩石和一些有机poor的岩石中观察到AIF-S签名为何（例如，Bifs和Carbonates），（例如，B），（b）为什么Aif-Speys niffeans nounder nounder ockes nounder ockes nounder of younter Rocks nounder in Youndroys nounder of Youndroys rocks ockes intern Youndroy sounter intern Youndroy; （3）沉积岩石中的AIF-S记录如何与地球早期的环境，化学和生物学进化有关：拟议的项目将是他的博士学位的一部分。论文研究和两名本科生（每年一名）作为研究助理。 PI计划与研究生研究员一起参加Wise计划：科学和工程研究所的女性。未来的学生和年轻科学家将从该项目产生的新数据和想法中受益。