Dynamic forcing of oxygen, iron, and manganese fluxes at the sediment-water interface in lakes and reservoirs

The National Research Council recently called for a more interdisciplinary approach to drinking water research to address the critical issue of global drinking water supplies. Hypolimnetic oxygenation systems (HOₓ) are being increasingly used to improve water quality in stratified reservoirs by increasing dissolved oxygen (O₂) concentrations and subsequently suppressing the release of soluble species such as iron (Fe) and manganese (Mn) from the sediment into the water. However, while the influence of HOx on the water column has been established, little work has been done on how oxygenation affects sediment O₂ uptake (i.e., sediment oxygen demand) and other sediment-water fluxes. In response to the growing need for alternative approaches for improving water quality, we conducted highly interdisciplinary research to evaluate how O₂, Fe, and Mn cycling at the sediment-water interface is influenced by both natural and HOx-induced variations in water column dynamics, chemical redox processes, and microbial activity within the sediment, all of which may govern sediment-water fluxes. Studies were performed in an alpine lake in Switzerland and in an HOₓ-equipped drinking-water-supply reservoir in Virginia. This research was based on in situ field campaigns paired with laboratory experiments, microbial analyses, and computer simulation to elucidate variable sediment O₂ uptake and corresponding Fe and Mn cycling. This work is unique in that sediment-water fluxes were assessed using in situ data from both sides of the sediment-water interface. Results show that sediment O₂ uptake flux is strongly controlled by both wind- and HOₓ-induced dynamic forcing. Our findings reveal that Fe and Mn fluxes were suppressed from the bulk hypolimnion via biogeochemical cycling in the oxic benthic region. Results also indicate that the sediment microbial community structure may directly respond to HOₓ-induced variation in sediment O₂ availability. Additionally, based on an analysis of the robustness of several commonly used methods for flux calculations, we show that flux estimates are not strongly dependent on the method chosen for analysis. Ultimately, by emphasizing the highly transient nature of sediment O₂ uptake, this research will aid in accurate characterization of various sediment-water fluxes and corresponding water quality. Our results will also directly contribute to the optimization of HOₓ operations and lake and reservoir management.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Civil Engineering

Department dc:contributor.department

Civil Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2010

Author dc:creator

• Bryant, Lee Davis

Chairs dc:contributor.committeechair

• Little, John C.
• Wueest, Alfred

Committee members dc:contributor.committeemember

• Vikesland, Peter J.
• Berg, Peter
• Eick, Matthew J.
• McGinnis, Daniel F.

• oxygenation
• manganese
• iron
• diffusive flux
• Turbulence
• Sediment
• Water

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Dc Identifier Other

etd-03312010-111229

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/77337