Department or Program

Geology

Abstract

The application of road salt (NaCl) as a deicing compound in the United States began in the 1930s, and the Hart Brook watershed, located in Lewiston, Maine, has experienced elevated specific conductivity (SpC) values presumably due to the road salt retention since the first measurement in 2011. While the year-long spatial and temporal changes of the road salt contamination in the Hart Brook remain unclear, the purpose of this study is to investigate the transport dynamics of road salt and its impacts on the water quality of this watershed over a period of a year, in the aim of improving the understanding and the regulations on the nonpoint sources of pollution in this area. From late March 2021 to mid-February 2022, water levels, SpC values, discharges, and major ions were analyzed from 7 sites on a biweekly/monthly basis. Consistent with former reports, Cl- concentrations in the watershed present signals to surpass the chronically toxic level of 230 ppm suggested by EPA during summer and winter, reaching 435 ppm and 430 ppm due to drought conditions and road salt applications, respectively. As the application of road salt contributes to most of the Cl- contamination in the watershed, increasing Cl- flux during fall and the overall molar ratio of 0.9192 between Na+ and Cl- indicate the road salt residence in soils. The significant difference between the annual Cl- input amounts from the government and the actual export amounts from the measurements may suggest the presence of unregulated private application of de-icing salt, salt retention from previous years, and extra sources of contamination outsides the watershed. The transport dynamics of the road salt were analyzed through the characterization of the infiltration rate of the watershed and an observed first flush event during a storm in July. Further analyses on the watershed sub-surface, soil conditions, and % ISC owned by private companies or residences are necessary to further understand the road salt transport mechanisms within Hart Brook.

Level of Access

Open Access

First Advisor

Johnson, Beverly

Date of Graduation

5-2022

Degree Name

Bachelor of Science

Number of Pages

101

Components of Thesis

1 pdf

Community Engagement

1

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