Chloride Dynamics in an Urban-Agricultural Stream

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Geography, Geology and the Environment


Eric Peterson

Mentor Department

Geography, Geology and the Environment


Freshwater quality in northern regions is threatened by salinization. Represented as rising chloride (Cl) concentration, salinization is linked to a dramatic increase in deicing salt (NaCl) application. The harmful impacts of elevated chloride levels are well documented and include freshwater acidification, mobilization of heavy metals, altered microbial communities, and degradation of water supplies. The threat posed by chloride salinization to aquatic ecosystems and anthropogenic water supplies make the study of watershed chloride dynamics imperative. While many studies have explored Cl dynamics at basin scales, few have explored the importance of stormflow to Cl load at high resolution in salt impacted streams. It is also unclear why salinization is observed in rural basins where salt application is minimal. Road salt contributes a portion, but no study has considered the role of agricultural Cl sources in salinization. This warrants a study exploring the roles of stormflow and agriculture in Cl dynamics. This study will: (1) investigate the importance of stormflow to Cl load and (2) estimate the contribution of agriculture to Cl load in an urban-agricultural stream. The study will be conducted in Sixmile Creek (SMC), which is part of an urban-agricultural watershed located in central Illinois. Two points on SMC will be sampled on a weekly basis and storms will be sampled at high resolution using an autosampler. Chemical data paired with discharge measurements will be used to Cl calculate load while ratios of Cl to Na and K will be used to assess Cl soruce. I predict stormflow is the main driver of Cl load and while agriculture will measurably contribute, road salt is the principal Cl load source.



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