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Publication Date

2022-05-09

First Advisor

Amy L. Rhodes

Second Advisor

Andrew Guswa

Document Type

Honors Project

Degree Name

Bachelor of Arts

Department

Geosciences

Keywords

road salt, wetlands, hydrology, geochemistry, Kampoosa Bog, water contamination, groundwater

Abstract

During winter, road salts (NaCl) are applied on roads to lower the freezing point of water which prevents the formation of ice. These salts become a source of contamination of nearby soils and water bodies through groundwater and surface runoff recharge. In wetlands adjacent to roads where salt accumulation is high, species diversity and distribution is altered. This often leads to the abundance of salt tolerant plants and other invasives. Here, we investigate the conditions for release and storage of road salt at Kampoosa Bog, a 0.7 km2 calcareous fen providing habitat to approximately twenty state endangered species. Kampoosa Bog is adjacent to a 1.9 mile stretch of Interstate 90 (Turnpike) and Rt 7 in Stockbridge and Lee, MA, USA. We used discharge, chloride mass flux, precipitation and road salt application data collected between Nov 2017 and Nov 2020 to quantify chloride storage and release at annual, monthly and daily scales. Groundwater chloride concentrations were used to identify dilution events and a multiple regression model was used to determine factors influencing the release of chloride from the fen. Measured groundwater chloride concentrations are higher (max = 222 mg/L) closer to the Turnpike and tend to decrease as distance from the Turnpike increases. From 2018 to 2020 the input of salt to the fen was more than double the outflux. This retention of salt is consistent with increases in deep groundwater chloride concentrations. We estimate that 285000 kg of chloride accumulated in the fen between Nov 2017 and Nov 2020. Seasonal trends in chloride export indicate net outflux is highest during non - salting months that are characterized by sustained discharge. The regression model showed 84% (r2 = 0.84) of the variability in chloride outflux could be explained by discharge at KB175, precipitation, air temperature and the amount of 2 chloride already in the fen (p < 0.05). There was no statistical evidence that salt application rates between 2018-2020 influenced chloride outflux which could indicate that the wetland’s response time to changes in salt application practices could be several years or decadal.

Rights

©2022 Wayne D. H. Ndlovu. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.

Language

English

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