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Browsing by Author "Tomasek, Abigail"

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    Denitrification in Agricultural Surface Waters: Quantifying the Effect of Environmental Parameters and Hydrologic Connectivity on Nitrate Uptake and Microbial Communities
    (2017-10) Tomasek, Abigail
    The development of synthetic fertilizer has led to increases in crop yields and allowed for global population growth over the past century. However, this increase in available nitrogen has greatly altered the global nitrogen cycle, including increased nitrate loading to surface water and groundwater in the Midwestern United States, with negative effects on human health and aquatic ecosystems. Therefore, there is a need for effective management strategies and an understanding of the mechanisms for nitrate transport and uptake. Denitrification, the microbiological reduction of nitrate to nitrogen gas, can be viewed as a net sink for reactive nitrogen in aquatic systems. Small areas, termed hot spots, and short time periods, termed hot moments, frequently account for a large portion of denitrification. This research focuses on identifying the environmental parameters and hydrologic regimes that promote denitrification, along with determining how parameters, denitrification rates, and microbiological communities are related at multiple temporal and spatial scales. At the finest scale, a recirculating laboratory flume was used to determine the effect of turbulence and organic carbon on denitrification rates and the microbial community. An outdoor experimental stream and flow-through basin in the Outdoor StreamLab at the St. Anthony Falls Laboratory (SAFL) were used to determine the effect of short-term inundation and periodic inundation on denitrification. At the largest scale, water and sediment samples were collected over two years from a field site in an agricultural watershed in Southern Minnesota. The objectives of this research were to: (1) determine how turbulence and organic carbon affect denitrification, (2) investigate how inundation and hydrologic connectivity leads to the formation of denitrification hot spots and hot moments, (3) quantify and correlate the driving environmental parameters of microbial denitrification and the differences in these relationships for in-channel and riparian locations in an agricultural watershed, (4) develop and evaluate functional relationships between environmental parameters and denitrification rates, and (5) identify how denitrifying gene abundances, denitrification rates, and environmental parameters are related across a hydrologic gradient from channels to riparian areas.
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    Watertown: New Directions in Building Connectivity Between People and Their River
    (Resilient Communities Project (RCP), University of Minnesota, 2015) Blomstrand, Garrett; Tomasek, Abigail; Takbiri, Zeinab; Schumann, Jennifer; Tofelde, Stephanie; Schulte, Mark
    This project was completed as part of the 2015-2016 Resilient Communities Project (rcp.umn.edu) partnership with Carver County. The Carver County Water Management Organization is investigating the feasibility of removing or restructuring a dam on the Crow River near downtown Watertown. The purpose of the removal/redesign is to improve the fishery in the river, reduce bank erosion, and potentially create an engineered whitewater recreation attraction to boost tourism in the area. The goal of this project was to assess the feasibility and potential impacts of removing the dam. Carver County project lead Paul Moline worked with a team of students in CEGE 8602: Stream Restoration Practice, to assess the potential impacts, benefits, and drawbacks of removing the dam. The students found that while removing the dam would decrease water elevation and impact flow velocity, it would also improve fish passage, better connect residents to the river, and provide safer recreation opportunities. The final report is available.