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The importance of sulfurized sugars for organic carbon burial: Testing the model in Santa Barbara Basin

硫化糖对于有机碳埋藏的重要性：在圣巴巴拉盆地测试模型

基本信息

批准号：
1436566
负责人：
Alex Sessions
金额：
$ 35.5万
依托单位：
California Institute of Technology
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2014
资助国家：
美国
起止时间：
2014-08-01 至 2018-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1436566&HistoricalAwards=false
关键词：
importance sulfurized sugars organic carbon

项目摘要

When organic matter is deposited in sediments, it undergoes a series of reactions that condense and transform the original organic molecules into a denser, more resistant set of compounds that form a material called kerogen: the material from which petroleum is formed. Our present understanding of how the original organic molecules change and crosslink (i.e., polymerize) to form kerogen during burial in sediments is poor. It has been hypothesized that the element sulfur plays a large role in the crosslinking; however, so far there is little direct evidence due to the absence of analytical techniques that can appropriately study the role of sulfur in this process. This research uses a newly developed, novel, analytical technique to measure the sulfur isotopic composition of individual molecular compounds in organic matter. This will allow the identification of the origin of the organic-bound sulfur and has the potential to revolutionize our understanding of the polymerization of natural organic matter, and hence formation of kerogen. Broader impacts of the project include determining fundamental physical and chemical relationships that allow better understanding of the carbon cycle, which has implications for the formation of kerogen and petroleum; building infrastructure for science via the development and refinement of a new and potentially powerful analytical technique and methodology; and graduate student training. It will engage under-represented minority undergraduate students via the California Institute of Technology Minority Undergraduate Research Fellowship program in order to help broaden participation of minority students in state-of-the-art research. The condensation and polymerization of biologically generated organic matter into kerogen is one of the key steps in the global carbon cycle because it determines whether organic matter will be remineralized (dissolved) or preserved and buried (turned into kerogen). Although sulfur is thought to play an important role in this process by crosslinking organic monomers, the precise mechanistic details of how this happens is unknown. This research uses a newly developed technique that couples gas chromatography with multi-collector inductively-coupled-plasma-mass-spectrometry (ICPMS). This allows analysis of the isotopes of sulfur of individual organic compounds. Using this technique it is possible to document compounds resulting from: (1) the reaction of lipids with hydrogen sulfide (HS-) in sediment porewaters over long timescales, and (2) the reaction of carbohydrates with polysulfide in the euxinic water column on very short timescales. Because these two processes have sulfur isotope (S-34) signatures that differ by almost 30 permil, the two different processes can be easily distinguished. Organic-rich sediments deposited in the Santa Barbara Basin will be analyzed and the results compared to those from sediments in the Cariaco Basin to see if the pilot study in the Cariaco, which is a sulfide-rich water column environment, hold true in more normal organic depocenters. Goals of the research include: (1) understanding how sulfurization, a main process in the cross-linking of organic molecules to form kerogen, works and how it relates to organic carbon preservation (2) seeing if the results from the Cariaco Basin are generalizable to other organic carbon depocenters, (3) examining whether the abundance of disulfide-bound compounds relate to the presence or absence of water column exunia, (4) determining whether disulfide-bound organic sulfur is always enriched in S-34 compared to unbound sulfurized lipids, and (5) seeing if the sulfur isotope values of individual organic sulfur molecules are representative of bulk organic sulfur.

当有机物质沉积在沉积物中时，它经历了一系列反应，这些反应将原始的有机分子浓缩并转化为更致密，更有抵抗力的化合物，形成了一种称为油母质的物质：石油形成的材料。我们目前对原始有机分子如何变化和交联的理解（即，在沉积物埋藏过程中形成干酪根的能力较差。据推测，元素硫在交联中起着很大的作用;然而，到目前为止，由于缺乏可以适当研究硫在该过程中的作用的分析技术，几乎没有直接的证据。本研究使用一种新开发的、新颖的分析技术来测量有机质中单个分子化合物的硫同位素组成。这将有助于识别有机结合硫的来源，并有可能彻底改变我们对天然有机物聚合以及干酪根形成的理解。该项目的更广泛影响包括确定基本的物理和化学关系，以便更好地了解碳循环，这对油母质和石油的形成有影响;通过开发和完善新的和潜在的强大分析技术和方法，建立科学基础设施;以及研究生培训。它将通过加州理工学院少数民族本科生研究奖学金计划吸引代表性不足的少数民族本科生，以帮助扩大少数民族学生对最先进研究的参与。生物生成的有机质缩聚成干酪根是全球碳循环的关键步骤之一，因为它决定了有机质是被矿化（溶解）还是被保存和埋藏（变成干酪根）。虽然硫被认为通过交联有机单体在这一过程中发挥重要作用，但这是如何发生的精确机理细节尚不清楚。本研究采用了一种新开发的技术，耦合气相色谱与多收集电感耦合等离子体质谱（ICPMS）。这允许分析单个有机化合物的硫同位素。使用这种技术，它是可能的文件化合物产生的：（1）在长时间尺度的沉积物孔隙水中的脂质与硫化氢（HS-）的反应，和（2）在很短的时间尺度的碳水化合物与多硫化物在富氧水柱的反应。由于这两个过程的硫同位素（S-34）特征相差近30 permil，因此可以很容易地区分这两个不同的过程。将对沉积在圣巴巴拉盆地的富含有机物的沉积物进行分析，并将结果与Cariaco盆地沉积物的结果进行比较，以了解Cariaco（富含硫化物的水柱环境）中的试验研究是否适用于更正常的有机沉积中心。研究的目标包括：（1）了解硫化作用（有机分子交联形成干酪根的主要过程）如何起作用，以及它与有机碳保存的关系;（2）了解Cariaco盆地的结果是否可推广到其他有机碳沉积中心;（3）检查二硫化物结合化合物的丰度是否与水柱exunia的存在或不存在有关;（4）确定与未结合的硫化脂质相比，二硫化物结合的有机硫是否总是富含S-34，以及（5）观察单个有机硫分子的硫同位素值是否代表本体有机硫。