Water Resources Research Act Program

Details for Project ID 2020IL218B

Utilizing a tracer test to calculating the transport and fate of nitrate within a saturated buffer zone

Institute: Illinois
Year Established: 2020 Start Date: 2020-03-01 End Date: 2021-02-28
Total Federal Funds: $9,887 Total Non-Federal Funds: $20,350

Principal Investigators: Eric W. Peterson

Abstract: Agricultural within the US Midwest has been identified as a significant non-point source of nutrientexport to the Mississippi River and the Gulf of Mexico. The excess nutrients, specifically nitrate (NO3-),contributes to eutrophication of surface waters and to the development of hypoxic zones. Development ofbest management practices (BMP) to decrease the export of NO3- in surface water focus on methods thatintercept and remove the NO3- before entering the stream. One BMP that has exhibited success in loweringNO3- concentrations is the diversion of tile-drain water into a saturated buffer zones (SBZ). Previousprojects have shown plant uptake and denitrification within the SBZ actively lowered the levels of NO3- ingroundwater. However, quantifying the loss on NO3- mass from the system has been stymied because theamount of dilution of the tile-water by groundwater is not well understood. The proposed project addressesthe single question “What role does dilution have on the observed decrease in nitrate as nitrogen (NO3-N)concentrations in a SBZ? Three objectives will be addressed to answer the question and advance ourunderstand of the effectiveness of SBZs to remediate excess NO3- from tile waters. The objectives include:1) Identify the flowpath of the waters traveling from the diversion tiles to the stream; 2) Measure the traveltime for the waters along the flowpath to the stream; and 3) Calculate the amount of dilution using a mixingmodel. A tracer test will be conducted to ascertain the movement of the tile-water through the SBZ. Sodiumbromide (NaBr) will be introduced into a tile-diversion box that redirects tile-water into a SBZ. Prior to theinitiation of the test and once every two weeks over 22 weeks, groundwater, tile water, and the stream waterwill be collected and analyzed for major anions. Mapping of the spatial and temporal variations in Br- willprovide an initial assessment of the flow pathways. Travel times will be calculated using breakthrough curveanalysis from waters obtained from downgradient wells. Mixing models will be used to assess whether theconcentration of NO3-N has been diluted or whether there has been a loss of mass from the system. Theproject serves as one facet of a larger collaborative project with the City of Bloomington (IL) to identifyBMPs designed to improve the water supply for the city. Identified BMPs will be transferable to otheragricultural areas of the state and region. The project will directly involve one Hydrogeology M.S. Programstudent from Illinois State University. The student will be involved in all aspects of the project: conductingthe tracer tests, collecting and analyzing the water samples, interpretation of the data and the disseminationand outreach aspects of the work.