Cassidy, Kathryn2023-02-032023-02-032022-11https://hdl.handle.net/11299/252318University of Minnesota M.S. thesis. November 2022. Major: Water Resources Science. Advisor: Chan Lan Chun. 1 computer file (PDF); vi, 105 pages.The application of sodium chloride as a deicing agent for winter road safety has deleterious effects, from corrosion to infrastructure, impaired water quality, and toxicity to flora and fauna. The salinity of freshwater across the United States has been rising for decades, with the main driver of this being road salts. As chloride is conservative in the environment, this salinization of freshwater is expected to continue unless chloride use is significantly reduced. Due to the threat of freshwater salinization and other negative impacts of sodium chloride, there is an ongoing search for effective and environmentally friendly deicing alternatives. One such alternative, potassium acetate, is the focus of this research. While the effectiveness of potassium acetate as a deicer is established, the environmental impacts of potassium acetate are less understood. Potassium acetate is biodegradable, and the process of microbial oxidation of acetate has the potential to severely deplete dissolved oxygen in waterbodies receiving inputs of potassium acetate. Potassium and acetate may reach toxic thresholds for vegetation and aquatic life, and potassium acetate has been shown to be a more toxic compound than sodium chloride. In order to investigate the environmental impact of the application of potassium acetate as a deicer, a field evaluation with biological oxygen demand (BOD) tests, biodegradation experiments, and toxicity assays was conducted. We found that collection of stormwater and receiving water body samples find expected concentrations of potassium and acetate in receiving water bodies to be negligible in large, well-mixed systems due to dilution. Potassium acetate application resulted in a very high BOD (average near 50 mg/L in highway runoff and > 2,000 mg/L in bridge deck runoff) in stormwater and a significant demand in less mixed receiving water (up to 400 mg/L). However, sufficient (> 9 mg/L) dissolved oxygen concentrations remained even in waters with a high oxygen demand due to the slow biodegradation of acetate (k = 0.02 day-1 at 4˚C) at low temperatures experienced in the field during the winter and spring. The acute LC50 to Ceriodaphnia dubia of CF7 as potassium is 130 mg/L, a low toxicity threshold given that the peak potassium concentration measured in the field evaluation was 560 mg/L. This acute toxicity threshold of potassium can be surpassed in smaller or less well mixed bodies of water. No adverse impacts of the deicer to roadside grasses were found at concentrations reported in the field. Potassium was found to be the agent of toxicity to freshwater zooplankton while acetate was responsible for toxicity to grass species. The findings from this research will inform salting practices as decision makers seek information on alternative deicers to keep roadways safe from ice while protecting our water resources.endeicingpotassium acetateroad saltThesis or Dissertation