The cycling of radionuclides through the macroflora of White Oak Lake

Author

Deborah Ann Mohrbacher

Date of Award

5-1992

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Major Professor

B. Gordon Blaylock

Abstract

This research investigation considers the role of aquatic macrophytes as one process influencing the transport and cycling of ^{137sup>Cs and 60Co in White Oak Lake and the weir pools of its two tributaries, White Oak Creek and Melton Branch by examining the mechanisms of plant uptake and decomposition.}

The source of radionuclides, the sediments or the water, to the rooted, submerged macrophytes Myriophyllum spicatum L. and Elodea canadensis L., was determined to evaluate their potential for remobilizing sedimented contaminants to the overlying water column. These plants accumulated approximately 30-50% of their ^{137sup>Cs content, and up to 67% of their 60Co content from the sediments versus the water column.}

The significance of macrophyte radionuclide remobilization was evaluated by quantifying the release of 137Cs and ⁶⁰Co from milfoil growing in situ during the processes of natural senescence and decomposition. Approximately 68% of the total ^{137sup>Cs and 35% of the total 60Co contained in Myriophyllum was released in a dissolved state to the water column during the course of senescence. The release was constant and linear over time. This is in contrast to litter bag studies also conducted using air-dried plants, where the radionuclides were released exponentially.}

Assessing the role macrophytes play in the transport and cycling of radionuclides in White Oak Lake is considered in relation to the total radioecology of the system. The composition, abundance, distribution and biomass dynamics in relation to their radionuclide content. This information, along with the data gathered from the uptake and decomposition studies, and measurements of various abiotic and physicochemical parameters were used to develop a dynamic compartmental box model of White Oak Lake to understand how macrophytes influence ^{137sup>Cs transport and cycling. Several manipulations of the system were modeled to simulate the system response under realistic, potential scenarios. The simulations showed that if the discharge of 137sup>Cs to the lake were to cease, the rooted, submerged plants would continue to contribute 137sup>Cs to the water column as a result of sediment remobilization.}

Recommended Citation

Mohrbacher, Deborah Ann, "The cycling of radionuclides through the macroflora of White Oak Lake. " PhD diss., University of Tennessee, 1992.
https://trace.tennessee.edu/utk_graddiss/10955