Sulfur Transformation In Soil/Sediment Profiles Of Two Contrasting Basin Systems Along Louisiana Coast.

Wetlands are considered to be one of the largest global sinks/sources of sulfur. Being exist in a variety of oxidation states, sulfur plays a major role in biogeochemical cycles of coastal wetlands. In the present study, we have evaluated sulfur chemistry in vertical profiles of coastal wetlands of two contrasting basins along the Louisiana coast. Core soil/sediment samples up to 380 cm depth were collected from wetland profiles of Atchafalaya and Barataria basins in southern Louisiana. The collected samples were sectioned, freeze-dried, grounded, and analyzed using sulfur k-edge x-ray absorption near-edge structure (XANES) spectroscopy. Results suggested that the salinity had a significant contribution to the speciation of sulfur oxidation states in these sediments. Areas experiencing high salinity levels exhibited an increased proportion of sulfur containing compounds having higher oxidation states; conversely, a greater proportion of reduced sulfur species was observed in coastal areas experiencing lower salinity levels. Highly oxidized sulfur compounds decreased as pyrite became the dominant compound along the soil profile depth. Overall, the results showed substantial alteration in reduced organic and inorganic sulfur within and between the two contrasting basin soils.