Date of Award

2001

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

S.F. Korom

Abstract

An experiment was conducted to determine if a decrease in the content of sulfides related to denitrification could be measured in the laboratory using sediments of the Elk Valley Aquifer in eastern North Dakota. The experiment entailed analyzing sediments for sulfides and solid organic carbon and isolating them in sample containers with a nitrate solution to determine if a measurable decrease in these components could be observed.

Previous denitrification studies in the Elk Valley Aquifer showed an increase in sulfate in conjunction with a decrease in the concentration of nitrate. Sulfate is a by product of autotrophic denitrification where sulfide is used as the electron donor by anaerobic bacteria to convert nitrate to harmless nitrogen gas.

Results of the laboratory study show that denitrification did occur in the samples, evidenced by the decrease in nitrate concentration and an increase in the concentration of dissolved inorganic carbon. Dissolved inorganic carbon is a by-product of heterotrophic denitrification where anaerobic bacteria utilize solid organic carbon as an electron donor. This finding is significant because it shows that sediments studied in-situ in the Elk Valley Aquifer reacted differently when they were studied in the laboratory.

Calculations were made to show the total amount of denitrification that would be possible based strictly on the content of sulfides and solid organic carbon. Conclusions based on rates of denitrification previously measured in the Elk Valley Aquifer and the theoretical potential of denitrification based on the electron donor content found in this study, suggest that the availability of electron donors in the sediments may be limited in regard to bacterially mediated denitrification.

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