University of Vermont
Amy Frappier, Graduate Student, Department of Earth Sciences
Anthropogenic Influences on Nitrogen Levels in Four Tested Vermont Ponds
Nitrogen (N) is a limiting nutrient in the environment; however, an overabundance of nitrogen can be catastrophic in most ecosystems. Significant anthropogenic contributions to the natural nitrogen cycle may be derived from the fertilizers that are incorporated into the hydrosphere from both surface runoff and water table penetration. The goal of this experiment is to detect the contributions of fertilizer-derived nitrogen through the use of the stable isotope signatures of N found in surface waters. Nitrogen isotopes afford scientists a means to quantify the contributions found in these surface waters. Nitrogen has two stable isotopes: 14N (which makes up 99.635% of all N) and 15N (which comprises 0.365%). Natural waters typically have nitrogen levels that are depleted with respect to 15N when compared to the atmosphere. In contrast, fertilizers made via the Haber process have higher, more atmospheric-like signatures. To detect the presence of fertilizer, I will use a mass spectrometer to measure the nitrogen isotopic composition of a suite of ponds from Vermont. The study suite includes waters from a pristine site in a Vermont State Park pond as well as two farm ponds, and a pond from an abandoned farm. I expect that the 15N/ 14N will be higher on the farmland ponds associated with active farms.