SGER: Clay Microfabric Signatures Driving Organic Matter Preservation in Marine Sediment: Micro- to Nano-scale Properties and Processes

University Of Southern Mississippi, Hattiesburg MS

Investigators

Abstract

Abstract: Proposal # - 0438079 The ability to observe, identify, quantitatively measure, and perform chemical and physical experiments with micro- and nanoscale barriers in fine-grained sediments has the potential to revolutionize our understanding not only of organic matter (OM) preservation in marine sediments, but also of fine-grained sediment structure and its effects on sediment physical properties such as porosity, permeability, and hydraulic conductivity. This project seeks to develop transmission electron microscope (TEM) and histochemical staining techniques that will allow imaging and analysis of both the undisturbed microfabric of fine-grained sediments and the distribution of specific organic compounds within the mineral matrix. Technique development will be initially carried out on artificially created model sediments of known composition and then applied to natural marine sediment aggregates. Natural aggregates for the pilot study will consist of polychaete worm fecal pellets. These were chosen because they are easy to produce and are easily reproducible in the laboratory by biomechanical means (i.e., passage of sediment through the worm's gut). They also contain two important end member clay microfabric signatures: (1) aligned face-to-face-oriented clay platelets (domain and "shingle") along the border of the pellets and (2) open organo-clay networks dominated by an edge-to-face fabric ("house of cards", or random arrangement of domains) in the pellet interior. Once the techniques can be reliably applied to natural samples, two pilot experiments designed to study the impact of clay microfabric on the preservation of OM in marine sediments will be performed to demonstrate the utility of the technique for addressing questions of importance to the marine science community. Broader impacts include providing a basis for other TEM-related technical approaches for studying OM preservation and storage in fine-grained marine sediments upon which other innovative TEM and sample preparations techniques can be built; providing a real-world basis for the development of models describing the behavior of OM trapped in organo-clay aggregates and the rates at which OM degrades with time and under different chemical, physical, and environmental conditions; and support of NSF goals in education, training, and gender and ethnic diversity.