Date of Graduation

12-2013

Document Type

Thesis

Degree Name

Bachelor of Science

Degree Level

Undergraduate

Department

Crop, Soil and Environmental Sciences

Advisor

Scott, Thad J.

Reader

Savin, Mary C

Second Reader

Brye, Kristofor R.

Abstract

The increasing environmental distribution of nitrogen has not only lead to changes in the global nitrogen cycle, but has also lead to many complex environmental consequences. Aquatic systems are particularly sensitive to high nutrient loading, and denitrification occurring in small lakes accounts for half the global release of dinitrogen. The objective of this study was to assess whether mixing events within the metalimnion increase denitrification rates. It was hypothesized that mixing events bring oxygen from the epilimnion and ammonium from the hypolimnion, simulating a coupled nitrification-denitrification process in the metalimnion. The dinitrogen-nitrogen (N2-N) concentration for three treatments of 0, 50, and 90% hypolimnion water samples represented mixing within the metalimnion and were measured to determine denitrification rates. The nitrate (NO3-) concentration was tested in order to determine if the insurgence of oxygen from a mixing event would increase nitrification and lead to a coupled nitrification-denitrification cycle. The results showed that denitrification occurred within the metalimnion; however, the 0% and 50% hypolimnion treatments had similar N2-N concentrations. The 90% hypolimnion treatment declined in N2-N concentration. Lack of increases in NO3- concentrations indicates that any products of nitrification proceeded directly to denitrification or microbial assimilation. The results show that the metalimnion of a reservoir can be a hotspot for denitrification, and provides opportunities for future studies to investigate the potential of metalimnetic denitrification. Metalimnetic water management can be a possible resolution for nitrogen removal from aquatic systems.

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