Date of Award
Master of Science (MS)
Department of Geography-Geology: Hydrogeology
Catherine M. O'Reilly
In areas dominated by agricultural land use, excess nitrate is one of the leading contributors to water pollution. Tile drains, installed to drain crop root zones for maximum yield, fast track the introduction of nitrate-laden water into a nearby stream. Due to the risks elevated levels of nitrate pose to an ecosystem and its inhabitants, the following project explores a method of reducing nitrate pollution. One that can do it as close to the source of the pollution as possible.
A tile draining a 60acre farm in central Illinois was redirected to discharge its contents through subsurface flow into an herbaceous riparian buffer zone (RBZ) located immediately below the farm. A transect of nested observation wells were installed across the riparian buffer intersecting the redirected subsurface tiles. A study on the groundwater and soils was performed to determine the ability the RBZ has for nitrate reduction/removal. Prior to redirecting tile water into the RBZ, chemical analysis of the RBZ water showed low concentrations of NO3-–N (≤5mg/L). The conditions necessary for the reduction/removal of nitrate, such as low levels of dissolved oxygen, dissolved organic carbon, and organic matter in the soils, and groundwater temperature were also investigated. A statistical comparison of the concentration of NO3-–N at the wells (effluent) vs the diversion box (influent) shows that the waters are significantly different (p<0.0001). Concentrations measured in the diversion box leading to the riparian buffer averaged 13.6 mg/L. Once this water had entered the riparian buffer however, the average concentration registered was lower than 1mg/L; a 94%reduction in the RBZ. The factors responsible for this reduction/removal such as dilution and denitrification are explored as well as any seasonal trends in nitrate removal.
Taye, Tamru Girma, "Reducing Nitrate Pollution by Redirecting Farm Runoff into the Subsurface of an Herbaceous Riparian Buffer Zone." (2016). Theses and Dissertations. 604.