Dissertation/Thesis Abstract

Analysis of trace element cycling in marsh pore waters of the lower Mississippi River Delta with a case study of vanadium in groundwaters of Texas and Nevada
by Telfeyan, Katherine Christina, Ph.D., Tulane University School of Science and Engineering, 2016, 232; 10143983
Abstract (Summary)

This dissertation combines field and laboratory work to examine how delta hydrology and sedimentology affects trace element cycling in marsh porewaters. This work was prompted by our lack of understanding of the hydrogeochemistry in the lower Mississippi Delta and how biogeochemical reactions affect fluxes of groundwater constituents to the ocean. In particular, I measured the concentrations of a suite of redox-sensitive trace elements (Fe, Mn, V, As) to determine the dominant geochemical reactions operating in marsh aquifers.

Because much more is known about As, I first conducted a study comparing V geochemistry along flow paths in a reducing sand aquifer in Texas and an oxidizing bedrock aquifer in Nevada. In agreement with other studies, V concentrations are much higher under oxidizing alkaline conditions. Under the reducing, circumneutral conditions of the Carrizo Sand aquifer, V concentrations are low but relatively constant, owing to complexation with dissolved organic matter. Similar observations regarding V geochemistry are observed in marsh groundwaters. Specifically, in pore waters of organic-rich sediment experiencing sulfate-reducing conditions, V concentrations are high owing to V complexation with organic matter, whereas in coarser-grained sediments, V may be removed from solution by adsorption. Arsenic geochemistry in pore waters varies as a function of depth. In the shallow subsurface, As concentrations are high and stabilized in solution by formation of thioarsenates. At depth, As appears to be sequestered through coprecipitation with pyrite.

Indexing (document details)
Advisor: Johannesson, Karen H.
Commitee: Flowers, George C., Kolker, Alexander S., Shiller, Alan M.
School: Tulane University School of Science and Engineering
Department: Earth and Environmental Sciences
School Location: United States -- Louisiana
Source: DAI-B 78/02(E), Dissertation Abstracts International
Subjects: Hydrologic sciences, Environmental Geology, Geochemistry
Keywords: Delta hydrology, Redox sensitive trace elements, Subterranean estuary
Publication Number: 10143983
ISBN: 978-1-339-99176-4
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