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Browsing by Subject "road salt"

Now showing 1 - 3 of 3
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    Demonstrating the potential for real-time groundwater monitoring using simple, continuous measurements
    (2024-05) McDaris, John
    With the growing reliance on groundwater resources in Minnesota and around the world, protecting the quality and quantity of water available is of increasing importance. The overarching goal of this work is to develop and test an innovative method of monitoring anthropogenic contamination of groundwater using high-frequency, real-time measurements of simple physical parameters. The infiltration of road salt chloride into regional aquifers can be utilized alongside specific conductance as a tracer in a wider investigation of human-caused changes to the groundwater system in the vicinity of the University of Minnesota, Twin Cities campus. A significant body of high-quality groundwater chemistry data has been collected by state agencies over the last half-century. Analysis of these data indicates that the concentration of anthropogenic chloride from road salt has been increasing in major TCMA aquifers over the last 50 years. The data also show that the thickness and composition of overlying geologic deposits have a great influence on current chloride concentration in any particular well. Similarly, consideration of hydrogeologic context is crucial for the interpretation of the relationship between chloride concentration and specific conductance. That same database was used to show that specific conductance is useful as a direct proxy of chloride concentration in some aquifers with especially robust statistical relationships. In units such as the Quaternary Water Table Aquifer (QWTA), specific conductance is more than 90% accurate in categorizing a modeled chloride concentration as below, between, or above the environmental water quality standards set by the state of Minnesota. In units without such a strong correlation, specific conductance can still provide a qualitative indicator of change over time in chloride concentration. Beginning in May, 2021, a pair of wells on the University of Minnesota Twin Cities campus were instrumented with sensors measuring specific conductance, temperature, and water depth. High-frequency measurements of these simple physical parameters created a temporally dense time-series of data that demonstrates continued infiltration of chloride from the surface to depth, transient localized changes in groundwater chemistry due to anthropogenic pumping, and increasing groundwater temperatures in the TCMA due to human activities and infrastructure. A network of sensors such as these, gathering real-time measurements, would have the power to resolve practical questions about the nature of groundwater networks and how chloride is moving through them as well as aid monitoring efforts for other conservative chemical species which are not as easily tracked. The results of these investigations demonstrate the feasibility of and need for a collaboratively developed sentinel network of real-time sensors distributed throughout the TCMA to provide high-frequency data on the state of the region’s groundwater.
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    The Environmental Impacts of the Use of Potassium Acetate as an Alternative Deicer
    (2022-11) Cassidy, Kathryn
    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.
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    Minnesota Shade Tree Advocate newsletter, volume 4, issue 1, winter 2001
    (2001) Minnesota Shade Tree Advisory Committee