Download or read book Geochemical Incorporation of Sulfur Into Organic Matter: Role of Sulfur in the Formation and Diagenesis of Macromolecular Organic Matter in Sediments written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In marine sediments, sulfur is intimately involved in organic matter diagenesis. While microbially-mediated sulfate reduction is well established as a major pathway for carbon mineralization, recent studies suggest an important role for reduced sulfur species as agents in the preservation of organic matter in marine sediments. The overall goal of this study was to improve the understanding of the role of sulfur in organic matter diagenesis. Two major objectives were outlined: (1) development and evaluation of structural models quantitatively describing organically-bound sulfur (OBS) in sediments; (2) application of these models for (a) assessment of sulfur incorporation into organic matter as a preservation (kerogen formation) mechanism and (b) elucidation of diagenetic pathways for organically-bound sulfur. The project built upon findings from a prior DOE grant. The experimental and theoretical approach is based on the premise that OBS can be represented as model structures that differ in S-linkage type (inter-molecular linkages vs intra-molecular bonds), as well as the number of linkages per molecule and the number of S atoms in each linkage. These models are pertinent for accurate prediction of organic carbon burial efficiency in sediments and delineation of temperature-time requirements for petroleum generation. An integrated analytical approach involving complementary techniques was used to provide compositional information on both carbon and sulfur geochemistry of sedimentary organic matter. Specifically, X-ray absorption (XANES) spectroscopy was used to quantify the proportions of organic sulfides, thiophenes and more oxidized species that together comprise organically-bound sulfur. Organic sulfur speciation was also examined using high pressure Temperature-Programmed Reduction (TPR). Chemical degradation experiments were employed to selectively cleave organic molecules linked by sulfur, providing information on linkage type (di- or polysulfide vs. monosulfide), the sites of sulfur attachment, and the molecular structures of the sulfur-containing molecules. Analytical pyrolysis was used to derive structural (carbon skeletal) information on insoluble organic matter fractions (kerogen) and to provide estimates on organic sulfur content. A unique aspect of this project involved the measurement of sulfur isotopic compositions of well-defined organic matter sub-fractions, including individual organic sulfur compounds. These data aided in elucidation of the timing and the mode of sulfur incorporation as well as the interrelationships between different co-existing organic sulfur species.