Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

First Advisor

William H. Patrick, Jr

Abstract

The amounts and profile distribution of various sulfur forms in Louisiana coastal marshes were investigated to understand sulfur cycling as related to the origin and type of tidal wetland marshes. Sampling was conducted quarterly from a Panicum hemitomon freshwater marsh, a Spartina patens brackish marsh, and a Spartina alterniflora salt marsh in Barataria Basin, Louisiana. Soil samples were fractionated into acid-volatile sulfides (AVS), elemental sulfur, HCl-soluble sulfur, pyrite sulfur, ester-sulfate sulfur, carbon-bonded sulfur, and total sulfur. Seasonal changes showed a greater effect on the distribution of S fractions in brackish and salt marsh than in the freshwater marsh. Season appeared to have a pronounced effect on the distribution of acid-volatile sulfides, elemental sulfur, and pyrite sulfur. The profile distribution of acid-volatile sulfides and elemental sulfur in all marshes was similar. These sulfur forms showed the greatest abundance in the oxidized zone ($<$20 cm) during spring, summer, and fall. Marsh soil oxidation processes occurring during the plant growing season and a falling water level over the marsh surface resulted in a low pyrite sulfur concentration in the surface. The maximum concentration of pyrite sulfur was observed below 20 cm in all marsh types and its concentration was relatively high during winter. The presence of HCl-soluble sulfur was contributed largely from pore water sulfate, which was greater in salt marsh than in brackish and freshwater marshes, respectively. Organic sulfur, in the forms of ester-sulfate sulfur and carbon-bonded sulfur, was the major contributor to the total sulfur pool in all marsh types. Carbon-bonded sulfur was generally 2 to 3 times more abundant than ester-sulfate sulfur with less seasonal variation. Sulfur concentration (volume basis) and sulfur accumulation rates increased from freshwater marsh to salt marsh. Reduced sulfur species removed by marsh accretion or sedimentation process are likely significant in marsh energy flow. Plant activity, tidal fluctuation, and distance along a salinity gradient from the Louisiana coast seemed to have a strong influence on the distribution of sulfur.

Pages

185

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