ABSTRACT Proposal Number: CTS-9703451 Principal Investigator: Hondzo This is a CAREER grant to study benthic boundary mixing within thermally stratified lakes. Field measurements will be conducted in five freshwater lakes. Turbulent properties of the benthic boundary layer will be investigated using a self-contained microprofiler augmented with the acoustic Doppler velocimeter. The internal wave characteristics within the lake basin will be measured with thermistor chains. Several issues will be addressed such as: (1) The primary mechanism for generating turbulence within the sloping boundary layer (2) The magnitude of the up slope volume flux and associated cycling time scales within the benthic boundary layer. (3) Determination of whether the turbulent boundary layer thickness is determined by the turbulent entertainment or by the internal wave characteristics near the sloping boundaries. and (4) Whether the vertical eddy diffusivity within the benthic boundary layer can be correlated with the dynamic stability (Lake Number) of the entire lake? Laboratory experiments will focus on the details of the interfacial gas transfer mechanism at the sediment-water interface. Near-bed liquid turbulence and dissolved oxygen (DO) concentrations will be also be measured in a laboratory channel over a wide range of Reynolds number, for a variety of bottom sediments. The determination of DO microprofiles in conjunction with characterization of near-bed turbulence will address a wide range of questions concerning the distribution of DO. The research results will provide an opportunity to validate the existing conceptual models, as well as enhance the development of new models which can improve our ability to predict water quality and transport related parameters in lakes, reservoirs, and coastal waters.
