Term of Award

Summer 2017

Degree Name

Master of Science in Applied Engineering (M.S.A.E.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Committee Chair

Francisco Cubas

Committee Member 1

Arpita Saha

Committee Member 2

Peter Rogers

Abstract

Mercury is potentially toxic to the environment. Mercury is absorbed into anaerobic sediments of surface waters, which may be converted to methylmercury, a toxic form of mercury that bio-accumulates in aquatic biota. Sources of mercury in the environment vary, but the production of methylmercury is common in sulfur-rich sediments containing mercury. In such environments, sulfur reducing bacteria (SRB) produce methylmercury as a by-product. The metabolic process uses energy from the reduction of sulfate to sulfide. This study focuses on determining the methylmercury production and release potential from sulfur-rich sediments extracted from different areas of the Brunswick Estuary. Previous studies note considerable levels of mercury in the Brunswick Estuary due to a local super fund site. Water and sediment samples were collected from six different sites to feed microcosms. The design measures the potential of the sediments to produce methylmercury. Microcosms were operated under anaerobic conditions to determine if sediments produced methylmercury under extreme conditions (e.g. low dissolved oxygen, low oxidation-reduction potential, and highly productive environment). This may seasonally exist in different zones of the estuary. Results revealed that sediments have the potential to reduce sulfate under anaerobic conditions. In the microcosms, sulfate concentrations rapidly decreased from values as high as 290 mg/L to practically 0 mg/L. This suggests that sediments provide an adequate environment to support SRB activity, which may result in methylmercury production. Further, results revealed that the production potential of methylmercury varies across different zones of the estuary. Precise methylmercury concentrations collected from the different sites are currently being evaluated. Due to the environmental conditions that prevail in the estuary, its proximity to a mercury super fund site, and its accessibility for fishing activities, it is crucial to further assess the methylmercury formation in this area.

Research Data and Supplementary Material

Yes

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