New insights on porewater geochemistry in organic-rich coastal sediments

dc.contributorLu, Yuehan
dc.contributorTick, Geoff
dc.contributorCherry, Julia A.
dc.contributor.advisorDimova, Natasha T.
dc.contributor.authorLamore, Alexander F.
dc.contributor.otherUniversity of Alabama Tuscaloosa
dc.descriptionElectronic Thesis or Dissertationen_US
dc.description.abstractPrevious studies of groundwater nutrient dynamics in coastal Baldwin County, AL indicate that groundwater is contaminated with NO3-. However, recently, nutrient fluxes' mass-balance indicates positive fluxes of reduced nitrogen species, NH4+ and dissolved organic nitrogen (DON), while NO3- fluxes were negative. Further, it was suggested that geochemical transformations within an organic-rich layer comprising the subterranean estuary (STE) in Mobile Bay could be responsible for the observed changes in the groundwater-derived nitrogen fluxes. This study aims to examine the nitrogen geochemical transformations occurring in organic-rich shallow coastal sediments and to identify the quantity and quality of carbon exported by groundwater. In a laboratory-based study, sediment cores with identified organic-rich layers collected from a hypoxia-impacted shoreline of Mobile Bay were incubated with 400µM and 800µM NO3- solutions, natural groundwater (GW), and ultra-pure carbon-free water (UPCFW) to evaluate how the sediment reacts to different NO3- loading. Findings from the incubation studies show that the organic-rich sediments are indeed responsible for the NO3- loss in groundwater as all treatments with NO3- amendments experienced NO3- removal. Also, that the organic-rich sediments are a source of reduced N, in the form of DON and NH4+, evidenced by net-N production observed in three of four treatments and the N produced correlates with DON, and that higher NO3- loading promotes increased DON production. Additionally both DNRA and denitrification occurred, but the dominant pathway of NO3- removal was denitrification. Average NO3- removal rates increased with increases in NO3- loading, but complete NO3- removal was not observed. The STE sediment has the potential to denitrify significant amounts of anthropogenic NO3-, however, in the process producing NH4+, DON, DOC, and DIC.en_US
dc.format.extent87 p.
dc.publisherUniversity of Alabama Libraries
dc.relation.hasversionborn digital
dc.relation.ispartofThe University of Alabama Electronic Theses and Dissertations
dc.relation.ispartofThe University of Alabama Libraries Digital Collections
dc.rightsAll rights reserved by the author unless otherwise indicated.en_US
dc.subjectEnvironmental geology
dc.titleNew insights on porewater geochemistry in organic-rich coastal sedimentsen_US
dc.typetext of Alabama. Department of Geological Sciences University of Alabama's
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