THE EFFECTIVENESS OF AN HERBACEOUS RIPARIAN BUFFER ZONE IN REMOVING NITRATE FROM A TILE DRAIN INPUT AT A LOW ORDER STREAM IN CENTRAL ILLINOIS

In areas dominated by agricultural land use, excess nitrate is one of the leading contributors of water pollution. Tile drains, installed to drain crop root zones, decouple farm water from interacting with the subsurface and instead transport and discharge the nutrient-rich water into a stream. Due to the risks elevated levels of nitrate have on humans (methemaoglobinemia) and on the ecosystem (hypoxia and eutrophication), the following project investigates a method of reducing nitrate concentrations from tile water in-situ. A tile, draining a 60acre farm in central Illinois, is redirected to discharge its contents into the subsurface of an herbaceous riparian buffer zone (RBZ) located between a farm and a stream. A transect of nested wells is installed across the riparian buffer intersecting the redirected tiles. These wells are used to observe the change in the chemistry of the tile water as it migrates through the RBZ and potentially loses its nutrients by interacting with the subsurface. A chemical and biochemical analysis of the study site will also be performed to determine suitability for nitrate removal. As a control, another transect of wells is installed away from any tile contact and its water observed. In-situ dissolved oxygen, temperature, and conductivity continue to be noted every two weeks using a YSI probe. Prior to redirecting tile water into the RBZ, chemical analysis of the RBZ water showed low concentrations of NO₃^--N (≤5mg/L) with the exception one set of well, which registered concentrations as high as 11mg/L NO₃^—N. The EPA has a limit of 10mg/L NO₃^--N. Once redirecting tile water to the RBZ began, the water table acted accordingly by rising but soon equilibrated, illustrating that the tile water is entering the system. At the time of submission, initial sampling of wells following diversion had been initiated but data are forthcoming. I expect to see wells nearest the redirected tile to have a higher concentration of NO₃^--N than before diversion. Moreover, this concentration is expected to decline as it migrates through the buffer.