Publication Date

2015

Document Type

Thesis

Committee Members

Christopher Barton (Committee Member), Chad Hammerschmidt (Advisor), Carl Lamborg (Committee Member)

Degree Name

Master of Science (MS)

Abstract

Monomethylmercury (MMHg) bioaccumulates in aquatic food webs, leading to concentrations in fish that increase health risks for humans who consume fish. As a result of processes that produce and decompose it, MMHg concentrations are notoriously unstable in many natural waters. I examined the stability of MMHg in both filter-sterilized (< 0.1 µm) reagent-grade water and 0.22-µm filtered sediment pore water from Grand Lake St. Marys, Auglaize and Mercer Counties, Ohio, each at three MMHg treatment concentrations (1, 5, and 50 ng/L). Reagent-grade water samples were incubated under both light and dark conditions at either 5 or 26 °C for 112 days. Pore water samples were incubated in the dark at 26 °C, mimicking environmental conditions, for a period of 98 days. Decay constants (± 95% CI) for solutions containing either 1 or 5 ng/L MMHg in reagent-grade water ranged from 0.0009 ± 0.0013 to 0.1225 ± 0.0150 d-1, with greater decay constants at higher temperature and no significant effect of light exposure. In contrast, decay constants for 50 ng/L MMHg in reagent-grade water were much less than those in more dilute solutions, ranging from 0.0018 ± 0.0015 to 0.0055 ± 0.0023 d-1, with both light and temperature influencing MMHg decomposition. Decay constants of MMHg in pore water were found to be independent of initial concentration of MMHg; however, decay constants in pore water samples were 3-fold higher than those in reagent-grade water amended with the same initial concentration (p = 0.007). These results suggest that natural constituents in pore water accelerate MMHg decay reactions.

Page Count

34

Department or Program

Department of Earth and Environmental Sciences

Year Degree Awarded

2015

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