The formation of organic sulfides by reaction of lipids with aqueous sulfides in three Holocene sediments

This thesis focuses on the formation of organic-sulfide compounds in recent sediments by the chemical reaction of sedimentary lipids and dissolved pore-water sulfides. This chemical reaction, termed natural sulfidization, converts individual organic compounds into high-molecular-weight, sulfide-rich sedimentary organic material and discrete organic-sulfides which are thought to be more resistant to the degradative conditions of early diagenesis than the original organic compounds. This process is widely accepted as an important diagenetic pathway for enhancing the preservation of organic matter during sediment burial. The analyses of sediments from two marine environments, the Santa Barbara Basin and the Peru margin upwelling zone, and a sulfate-containing lacustrine environment, Mud Lake, FL are the focus of these investigations. The concentrations and stable carbon-isotopic compositions of sulfidized compounds and unreacted compounds with the same carbon skeleton are compared in these sediments to determine reaction pathways for the sulfidization of lipids. Additionally, a laboratory sulfidization study of the reaction of model compounds containing functional groups that are structurally similar to those found in recent sediments with aqueous solutions of sodium tetrasulfide and H;Despite the high organic carbon contents in each of the environments and high concentrations of reactive lipid components, organic-sulfide formation was not extensive in the Peru margin or Santa Barbara Basin sediments or the uppermost sediments from Mud Lake. For example, the upper 100 cm of Mud Lake contains high concentration of n-alkenes, which were shown to be reactive in the model compound study under aqueous conditions, but no evidence for their sulfidization was found.;Direct evidence for the role of polysulfides in the sulfidization of lipids in Mud Lake sediments below 100 cm was provided by the discovery of polysulfide-bound n-alkanes and C...