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Graduation Term

Summer 2025

Degree Name

Master of Science (MS)

Department

Department of Geography-Geology: Hydrogeology

Committee Chair

Eric Peterson

Committee Member

Lisa Tranel

Committee Member

Jonathan Thayn

Abstract

The widespread use of nitrogen-based fertilizers in agricultural fields has led to a significant increase in nitrate concentrations in soil and water, posing a significant threat to human health and aquatic ecosystems. Additionally, freshwater systems are increasingly experiencing salinization due to several factors, including the use of road de-icing salts, agricultural runoff and industrial discharges, which compound water quality challenges. These environmental concerns raise interest in understanding the factors influencing nitrate loss processes. One factor is the concentration of chloride. Chloride levels as low as 100-200 mg/L are believed to inhibit nitrate loss. This study focuses on understanding the impact of chloride on nitrate loss within sediment using column studies. Solutions with 15 mg/L nitrate as nitrogen (NO3-N) with added concentrations of chloride (Cl- ), 0 mg/L (control), 50 mg/L, 100 mg/L, and 1000 mg/L were run through sediment columns to assess the role chloride concentration has on the rate of nitrate loss. The results showed that at chloride concentration of 0 mg/L, nitrate concentrations began to decrease at 21 hours, reaching a low of 0.59 mg/L at 50 hours, indicating significant nitrate loss. However, three trials conducted at chloride concentrations of 50 mg/L, 100 mg/L and 1000 mg/L showed no nitrate loss within the sediment over 192 hours of experiment. Nitrate concentration remained almost constant at 15 mg/L suggesting that high chloride concentrations completely inhibit nitrate reduction processes within the sediment, further supporting my hypothesis that higher chloride levels inhibit nitrate loss. These findings highlight the importance of chloride contamination in freshwater systems, as elevated chloride levels can impede nitrate loss processes, potentially increasing water quality challenges such as eutrophication and posing long-term risks to human health and aquatic ecosystems. Reducing chloride inputs into water systems may enhance nitrate removal and improve water quality management efforts.

Access Type

Thesis-ISU Access Only

DOI

https://doi.org/10.30707/ETD.1763755358.895994

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