Author

Ndenga

Date of Award

4-2005

Degree Name

Master of Science

Department

Geological and Environmental Sciences

Department

Geosciences

First Advisor

Dr. Carla M. Koretsky

Second Advisor

Dr. Alan Kehew

Third Advisor

Dr. Johnson Haas

Access Setting

Masters Thesis-Open Access

Abstract

This research was aimed at: 1) quantifying redox-sensitive parameters in order to study redox stratification of the upper freshwater sediments at Asylum Lake and Kleinstuck Marsh, 2) quantifying the speciation of metals (e.g., Pb, Mn, Fe, Cr, Cu, Zn, Co and Cd), particularly with respect to their association with Fe and Mn (hydr)oxide phases, and 3) assessing changes in redox stratification and metal speciation as a function of season in the sediments. Both the solid phase and sediment pore waters were collected to a depth of ~50cm. Pore waters were analyzed for redox-sensitive species and the sediment solid phase was analyzed for % organic matter, porosity and metal concentrations using extraction methods proposed by Tessier et al. (1979) and Kostka and Luther (1994).

The results of the study show clear seasonal variations in trace metal speciation and redox stratification of the sediments. The presence of higher concentrations of organic matter leads to more reducing conditions in Kleinstuck Marsh compared to Asylum Lake; at both sites sediments have more compressed redox strata in summer compared to winter. Fe, Pb, Cu and Zn were mostly associated with the oxidizable fraction, and Mn with the carbonate and the FMO fractions of the sediment.

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