Initial application of novel compound-specific 34S analysis to the Cariaco Basin

硫是许多地球化学过程的重要组成部分，包括大气化学和气溶胶形成、微生物生态学、海洋缺氧和质量分解、有机物保存、石油生成和酸化以及古地球海洋和大气的氧化。硫物种的稳定同位素组成（即，它们的dS值）可以在这些研究中提供相当多的见解，因为硫的许多氧化还原转化诱导大的和诊断性的同位素分馏。这些分馏物可以保存在含硫产品中，作为过去工艺的指纹。在这方面，有机硫（OS）是硫同位素信息最丰富“但利用最少”的储存库之一。直到最近，还没有有效的方法来访问个别OS化合物记录的同位素信息。PI最近开发了一种新的GC/ICPMS分析方法（Amrani等人，2009），现在允许我们测量仅含有皮摩尔S的单个OS化合物中的d34 S。他们建议研究沉积成岩作用期间有机化合物的逐步硫化作用。三个具体的问题将解决有关的硫化脂质：i）d34 S值的个别化合物记录同化与异化途径的硫掺入？ii）分子d34 S值是否由于分馏而偏离其无机S源？不同的化合物是否记录了不同深度的硫化物和/或硫酸盐d34 S值？该提案将有助于支持开发和部署一种重要的新分析工具，即特定化合物d34 S分析。他们的研究结果和该方法更广泛的潜力可能会影响我们对全球碳循环的理解，以及对气候变化的所有深远影响，因为人们对硫化作用的认识仍然很差。该提案还将支持加州理工学院的一名博士生的教育，该博士生（完成后）可能会成为化合物特定S同位素分析的世界专家，并将该技术带到其他实验室。

Sulfur is an important component of many biogeochemical processes, spanning atmospheric chemistry and aerosol formation, microbial ecology, ocean anoxia and mass extinctions, organic matter preservation, petroleum generation and souring, and the oxygenation of the ancient Earth's oceans and atmosphere. The stable isotopic compositions of sulfur species (i.e., their dS values) can provide considerable insight in these pursuits, because many redox transformations of sulfur induce large and diagnostic isotopic fractionations. These fractionations can be preserved in sulfur-bearing products, where they serve as fingerprints of past processes. In this regard, organic sulfur (OS) is among the richest "but least utilized" reservoirs of S-isotopic information. Until recently there has been no effective way to access the isotopic information recorded by individual OS compounds. The PIs have recently developed a novel GC/ICPMS analytical approach (Amrani et al., 2009) that now allows us to measure d34S in individual OS compounds containing just picomoles of S. They propose to study the progressive sulfurization of organic compounds during sedimentary diagenesis. Three specific questions will be addressed regarding the sulfurization of lipids: i) Do d34S values of individual compounds record assimilatory versus dissimilatory pathways of sulfur incorporation? ii) Are molecular d34S values offset from their inorganic S sources as a result of fractionations? iii) Do different compounds record sulfide and/or sulfate d34S values from different depths? This proposal will help support the development and deployment of an important new analytical tool, namely compound-specific d34S analysis. The results of their research and the broader potential of the method are likely to impact our understanding of the global carbon cycle, and all of its far-reaching impacts on climate change, because the still poorly understood pathways of sulfurization exert a first-order control on the burial and preservation of organic matter in sediments. The proposal will also support the education of a PhD student at Caltech, who (upon completion) will presumably be the world's expert in compound-specific S isotope analyses and will carry this technique to other labs.