Master of Science (MS)
Oceanography and Coastal Sciences
Since the industrialization of the Haber-Bosch process in the 1940’s, anthropogenic activity has nearly doubled the Earth’s nitrogen fixation. Furthermore, nitrate has become the number one groundwater contaminant in the United States and has harmful effects such as eutrophication, algal blooms, and pollution of drinking water. Soils from two sites influenced by high nitrate loading were examined to determine their biogeochemical integrity. First, the Loosahatchie Bar, located northwest of Memphis, Tennessee, is influenced by excess surface water nitrate loading by the Mississippi River. The Loosahatchie Bar is a newly restored wetland that now has similar hydrologic influence to an upstream control site. The upstream control site and the restored bar sites are both bottomland hardwood forest but exhibit very dissimilar soil properties and microbial functions. Significant differences (P < 0.05) between the control and restored sites were observed for moisture content, bulk density, total carbon, nitrogen, and phosphorus, microbial biomass nitrogen, potentially mineralizable nitrogen, and potential denitrification. Second, the Tallahassee Wastewater Treatment Plant, located just southeast of Tallahassee, Florida, receives high nitrate loads to spray field pivot soils from Tallahassee, Florida’s municipal wastewater. Although the intended function of the spray field pivots is to remove excess nitrate from the wastewater, there has been observed eutrophication in Wakulla Springs 17.5 km south of the treatment facility. Soil analysis was conduced to compare the pivot soils with an up gradient control site. Significant differences (P < 0.05) were observed for moisture content, percent organic matter, total carbon, nitrogen, and phosphorus, and denitrifying enzyme activity. Carbon amendment experiments were conducted on the pivot soils with residual biosolids and corn plants. There were no significant differences (P > 0.05) observed for potential denitrification with either carbon amendment. More research should be done to understand water retention at these sites and the microbial communities involved in denitrification.
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Theriot, Jared M., "The effects of carbon on nitrogen transformations in restored wetland and wastewater soils" (2012). LSU Master's Theses. 3172.
White, John R.