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Publication Date

2024

Document Type

Poster

Degree Type

Graduate

Department

Geography, Geology and the Environment

Mentor

Dr. Wondessen Seyoum

Mentor Department

Geography, Geology and the Environment

Abstract

The exponential rate of nitrogen fertilizer applied to agricultural farmland, aimed at increasing crop productivity, has led to the leaching of nitrate beyond the root zone. This leaching occurs through the discharge of subsurface tile flow, leading to nitrate contamination in water bodies. The State of Illinois applies around 7.7 billion kilograms of nitrogen fertilizer to corn fields annually. This has become a major regional concern, as it threatens the terrestrial environment and aquatic ecosystems, causing dead zones due to eutrophication. To mitigate this problem, various management practices, such as the Saturated Riparian Buffer (SRB), were implemented. Natural and anthropogenic inputs of nitrate load under certain hydrogeological conditions, such as hydraulic conductivity and subsurface thickness, play a pivotal role in controlling nitrate reduction in SRB. The objectives of the study are to (1) assess how the variability of subsurface thickness affects nitrate reduction in the SRB; (2) evaluate how various inputs of nitrate load (mass) affect nitrate reduction within the (SRB); and (3) quantify the mass of NO3—N transported out of the SRB. Hence, this study will employ a 3D reactive contaminant transport model that will be used as tool for understanding nitrate transport and fate within an agricultural area. The model will be developed in Groundwater Modeling System software and will consist of three geologic layers ranging from the dark rich organic topsoil, mix of silty-clay thin sand unit, and diamicton, that will used to build the hydro-stratigraphy of the model. No flow boundaries will be assigned at the north and southern boundaries of the model, specified head at the east, the head-dependent boundary at the west, and recharge and no flow boundary at the top and bottom of the boundary, respectively. Water samples will be collected during Spring, Fall, and Winter for nitrate sampling and water level from 38 wells as well as from the stream adjacent to the study area, which will be used in calibrating the reactive transport model. The mass budget calculation from the model scenario analysis will be used to estimate the mass of nitrate out of SRB. It is expected that nitrate reduction should be highest during the Spring compared to nitrate reduction in the Fall and Winter due to the influence of tile flow. This study will help implement effective SRB designs and enhance our understanding on the efficiency of the Saturated Riparian Buffer in reducing nitrate pollution from agricultural runoff.

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