Collaborative Research: Oxidant Isotopic Fractionation during Early Organic Matter Diagenesis in Marine Sediments

合作研究：海洋沉积物早期有机质成岩过程中的氧化剂同位素分馏

• 批准号: 0117796
• 负责人: Jay Brandes
• 金额: $ 22.79万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-01 至 2005-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0117796&HistoricalAwards=false
• 关键词: Collaborative; Research; Oxidant; Isotopic; Fractionation

ABSTRACTOCE-0117796In order to use either O2 or nitrogen for current or paleo isotopic studies of their respective marine cycles, it is imperative that we know their fractionation during sedimentary consumption and if possible determine the mechanisms. A few estimates of O2 and NO3- isotope fractionation during sedimentary consumption have been made which showed that fractionation was much less (approaching zero) than the theoretical ones. Because these observations were made only in the eastern North Pacific where productivity is high and mid-water oxygen levels are low, two research investigators from the University of Washington and the University of Texas Marine Science Institute plan to carry out a laboratory methods development and field experimentation exercise to address two questions. Question number one asks whether the near absence of isotopic fractionation observed for both oxygen consumption and denitrification in highly respiring sediments of the Pacific Northwest continental margin a ubiquitous characteristic of shelf and upper slope sediments. The second question asks to what extent N2 production and the lack of N and O isotopic fractionation is related to abiotic or microbially mediated reoxidation of reduced products of metabolism. The PIs will conduct a field program in the Gulf of Mexico to (1) measure oxidant isotopic fractionation of O2 and NO3-, as well as related species such as N2 and NH4+ in incubated sediments, both on deck and in-situ; (2) conduct on-deck core manipulation experiments with added substrates (NO3-, 15NO3-, HN4+, 15HN4+, organic material and reducing substances) and inhibitors to elucidate possible mechanisms of isotopic fractionation and (3) make porewater and benthic chamber measurements of diagenesis rates to help elucidate the processes responsible for fractionation or lack thereof.

为了将O2或氮用于其各自海洋循环的现代或古同位素研究，我们必须了解它们在沉积消耗过程中的分馏，并在可能的情况下确定其机制。 在沉积消耗过程中，O2和NO3同位素分馏的一些估计表明分馏比理论值小得多（接近零）。由于这些观测只在北太平洋东部进行，那里的生产力很高，中层水的含氧量很低，来自华盛顿大学和得克萨斯大学海洋科学研究所的两名研究人员计划进行实验室方法开发和实地实验，以解决两个问题。 第一个问题是，在太平洋西北大陆边缘高度呼吸的沉积物中观察到的氧消耗和反硝化作用的同位素分馏几乎不存在，这是否是陆架和上斜坡沉积物的普遍特征。 第二个问题是问在何种程度上N2的生产和缺乏N和O同位素分馏与非生物或微生物介导的还原代谢产物的再氧化有关。 PI将在墨西哥湾进行一项实地项目，以（1）在甲板上和现场测量O2和NO3-的氧化剂同位素分馏，以及孵化沉积物中的相关物质，如N2和NH 4 +;（2）进行甲板上岩心操作实验，（NO3-，15NO3-，HN4+，15HN4+，有机物质和还原物质）和抑制剂，以阐明同位素分馏的可能机制，以及（3）进行孔隙水和底栖室成岩速率测量，以帮助阐明造成分馏或缺乏分馏的过程。