Chloride and Sulfate Concentrations of Milwaukee Waters During the COVID-19 Shutdown
Mentor 1
Russell Cuhel
Mentor 2
Carmen Aguilar
Mentor 3
Steven Levas
Start Date
16-4-2021 12:00 AM
Description
Human activities in urban centers can alter the chemical composition of local waters via processes such as wastewater discharge and rainwater runoff. Rarely is there an opportunity to study urban waterways in the absence of these influences. The 2020 COVID-19 shutdown in Milwaukee, Wisconsin—a temporary, near total cessation of commercial, social, and industrial activities in the city— provided one such opportunity. Changes in local water chemistry were assessed among samples collected during early-shutdown, mid-shutdown, and late-shutdown (partial recovery) conditions. Here I focus on conservative chloride and semi-conservative sulfate concentrations. Analyses were carried out via automated anion column chromatography on water samples taken from locations along the Mukwonago, Menomonee, Kinnickinnic, and lower Milwaukee rivers, in the outer Milwaukee harbor, and up to 25 km offshore into Lake Michigan. Comparison of water chemistry between the different stages of the shutdown and to samples predating the shutdown may elucidate the extent to which urban activities affect local water chemistry. Sulfate concentrations are generally unaffected by local activity due to being held constant by biogeochemical influences. Chloride mostly originates from groundwater, which was unlikely to be affected by the shutdown. Chloride can also enter surface waters via urban runoff, which may have been affected by the shutdown, though road salt (a major source of chloride runoff) is not a factor during the summer. However, comparisons between pre- and mid-shutdown conditions (controlling for seasonal variation in water chemistry by comparing only between expeditions undertaken on similar dates) show no significant change in either chloride or sulfate concentrations due to the COVID-19 shutdown. Other, typical variations in chloride concentration—dilution of river water (5-fold or more) entering the lake, or surface dilution by recent rainfall—are still evident.
Chloride and Sulfate Concentrations of Milwaukee Waters During the COVID-19 Shutdown
Human activities in urban centers can alter the chemical composition of local waters via processes such as wastewater discharge and rainwater runoff. Rarely is there an opportunity to study urban waterways in the absence of these influences. The 2020 COVID-19 shutdown in Milwaukee, Wisconsin—a temporary, near total cessation of commercial, social, and industrial activities in the city— provided one such opportunity. Changes in local water chemistry were assessed among samples collected during early-shutdown, mid-shutdown, and late-shutdown (partial recovery) conditions. Here I focus on conservative chloride and semi-conservative sulfate concentrations. Analyses were carried out via automated anion column chromatography on water samples taken from locations along the Mukwonago, Menomonee, Kinnickinnic, and lower Milwaukee rivers, in the outer Milwaukee harbor, and up to 25 km offshore into Lake Michigan. Comparison of water chemistry between the different stages of the shutdown and to samples predating the shutdown may elucidate the extent to which urban activities affect local water chemistry. Sulfate concentrations are generally unaffected by local activity due to being held constant by biogeochemical influences. Chloride mostly originates from groundwater, which was unlikely to be affected by the shutdown. Chloride can also enter surface waters via urban runoff, which may have been affected by the shutdown, though road salt (a major source of chloride runoff) is not a factor during the summer. However, comparisons between pre- and mid-shutdown conditions (controlling for seasonal variation in water chemistry by comparing only between expeditions undertaken on similar dates) show no significant change in either chloride or sulfate concentrations due to the COVID-19 shutdown. Other, typical variations in chloride concentration—dilution of river water (5-fold or more) entering the lake, or surface dilution by recent rainfall—are still evident.
