Characterization of Sulfur Chemistry in Louisiana Coastal Wetland Soils Using X-Ray Absorption Fine Structure (XAFS) Spectroscopy
Semester of Graduation
Master of Science (MS)
Plant, Environmental Management and Soil Sciences
Sulfur is one of the most abundant elements in the environment, which plays a vital role in the growth and functioning of plants and microorganisms. It is found in an extended variety of species in gases, liquid, and solid forms and present in various nature systems. Wetlands are one of the largest global sinks/sources of sulfur. Being existing in a variety of oxidation states, sulfur contributes to biogeochemical cycles of coastal wetlands through involving in humification processes as well as influence on metal sulfide formation and consequently, methanogenesis and greenhouse gas emission. In this study, we have evaluated sulfur chemistry in surface and vertical profiles of coastal wetlands along salinity gradients and in two contrasting basins along the Louisiana coast. For this purpose, we chose Barataria baisn, experiencing land loss, and Atchafalaya basin, undergoing delta growing and land building process. Sulfur chemistry in soil composite profiles (up to 50 cm depth) and vibracores (up to 380 cm depth) were collected from wetland ecosystems of Barataria and Atchafalaya basin in southern Louisiana. The collected samples were analyzed using sulfur K-edge x-ray absorption near-edge structure (XANES) spectroscopy. Results suggested that salinity had a significant contribution to the speciation of sulfur oxidation states on these soils. Soils experiencing high salinity levels exhibited an increased proportion of sulfur containing compounds and higher oxidation states of sulfur in these wetland ecosystems. Conversely, a greater proportion of reduced sulfur species and organic compounds was observed in coastal areas experiencing lower salinity levels and in lower depths of the vibracore profiles, which are geochemically more stable. Highly oxidized sulfur compounds decreased as pyrite became the dominant compound along the soil profiles. The presence of organic disulfides inversely affected pyrite formation. Overall, the results showed substantial alteration in reduced organic and inorganic sulfur within and between the two contrasting basin soils.
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Dehghani Tafti, Negar, "Characterization of Sulfur Chemistry in Louisiana Coastal Wetland Soils Using X-Ray Absorption Fine Structure (XAFS) Spectroscopy" (2016). LSU Master's Theses. 4549.
Available for download on Tuesday, July 30, 2024