Date of Graduation

5-2013

Document Type

Thesis

Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level

Undergraduate

Department

Crop, Soil and Environmental Sciences

Advisor

Scott, Thad J.

Reader

Brye, Kristofor R.

Second Reader

Savin, Mary C

Abstract

Denitrification in metalimnetic water was examined under different conditions to determine how of addition of nitrate (NO3-) and particulate carbon (PC), aeration, and concentrations of nitrate affect denitrification. In the first experiment, water samples from a metalimnion were treated with different combinations of NO3- and PC to find out how addition of NO3- and PC changes denitrification occurring in a metalimnion. The treatments included 1) control, 2) samples amended with 1 mg NO3− - N/L, 3) samples amended with both NO3− (1 mg NO3− - N/L) and PC (5.7 mg C/L), and 4) samples amended with 5.7 mg C/L. Changes in excess N2-N concentration for 10 days were measured using membrane inlet mass spectrometry (MIMS). In the second experiment, the same treatments were used to evaluate the effect of aeration. Besides excess N2-N concentrations, O2 concentrations were measured for 16 days. The third experiment examined how different initial concentrations of NO3- influenced denitrification, and changes in the samples with the four different concentrations of 1) control with 0 mg NO3− - N/L, 2) 1.0 mg NO3− - N/L, 3) 2.5 mg NO3− - N/L, and 4) 5.0 mg NO3− - N/L were measured using MIMS for 42 days. The first experiment indicated that all samples in this experiment had completed denitrification before this experiment, and denitrification occurred only in the samples added with NO3−. Aeration event in the second experiment resulted in low initial excess N2-N concentrations, and excess N2-N concentrations increased most in the samples containing both PC and NO3− and second most in PC amended samples. Excess N2-N concentrations did not increase in other two treatments, indicating the effect of PC on creating anoxic conditions for denitrification. Differences in initial NO3− concentrations did not result in differences in denitrification.

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