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.
|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|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be