Dissertations and Theses @ UNI
Availability
Open Access Thesis
Keywords
Nitrates--Environmental aspects--Cedar River Watershed (Minn and Iowa); Water--Nitrogen content--Cedar River Watershed (Minn and Iowa); Water--Pollution--Cedar River Watershed (Minn and Iowa); Groundwater flow--Cedar River Watershed (Minn and Iowa); Groundwater flow; Nitrates--Environmental aspects; Water--Nitrogen content; Water--Pollution; United States--Cedar River Watershed; Academic theses;
Abstract
Stable isotopes of nitrogen were used to assess the source and fate of nitrate in the Cedar River Watershed, Iowa. Ground water samples from 20 private wells and surface water samples from 10 sites in the Cedar River and its tributaries were collected. A total of 90 samples were collected during the growing season from May through September 2006. In 35% of the wells, nitrate concentration exceeded the U.S. Environmental Protection Agency's recommended maximum contaminant level (MCL) of 45 mg/1 (as NO3-) for drinking purposes. Eight (8) out of 10 samples exceeded MCL for nitrate in the first set of surface water samples collected, but none exceeded in the second and the third set. Nitrate concentration ranged from below detection to 75.5 ppm in ground water, whereas surface water nitrate ranged from below detection to 58 ppm during the study. High nitrates in water are characterized by high agricultural activities. Nitrate concentration also varied with well depths. Levels were higher in the bedrock aquifers than in the alluvial aquifers. Onsite parameters such as Dissolved Oxygen (DO), pH, Total Dissolved Solids (TDS), Conductivity, and Temperature were tested during this study. Most of the values were within the EPA's MCL for these parameters. Observed chloride concentration suggested that sewage contamination was not an issue in the area water. þÿÃ15N values from +0.450 %0 to+ 5.346 %0 were detected in ground water, suggesting commercial fertilizers and soil organic nitrate as the potential sources of nitrate. Lower þÿÃ15N values, higher nitrate concentration, and higher DO content in ground water suggested that denitrification was unlikely in the area's ground water. Similarly, þÿÃ15N values from +1.481 %0 to+ 5.164 %0 were found in the area's surface water, suggesting commercial fertilizers, soil nitrate, and possible isotopic fractionation as the originating sources of nitrate in the surface water. Possible fractionation by denitrification or nitrification was not supported by the observed DO, nitrate, and þÿÃ15N values. Also, animal wastes (including humans) were not found as the source of nitrate in any of the samples. From this study, it can be said that the nitrogen isotope technique is useful in both the source identification and the nitrogen transformation studies. Future research should be directed to the use of dual isotope techniques.
Year of Submission
2007
Degree Name
Master of Science
Department
Department of Geology
First Advisor
Mohammad Z. Iqbal
Second Advisor
James C. Walters
Third Advisor
Maureen E. Clayton
Date Original
2007
Object Description
1 PDF file (116 leaves)
Copyright
©2007 Sushil Gautam
Language
en
File Format
application/pdf
Recommended Citation
Gautam, Sushil, "Assessment of the Source and Transformation of Nitrate in the Cedar River Watershed by Using Stable Isotopes of Nitrogen" (2007). Dissertations and Theses @ UNI. 2715.
https://scholarworks.uni.edu/etd/2715
Comments
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