A study was conducted to generate knowledge on the environmental effects of de-icing salt, particularly sodium
chloride (NaCl), on water quality in Minnesota, especially the Twin Cities Metropolitan Area (TCMA). The
Mississippi River receives substantial sodium chloride inputs from the Minnesota River and waste water treatment
plants as it passes through the TCMA. In addition, road salt applications in the TCMA use about 350,000 short tons
of NaCl every year. A chloride budget at the scale of the TCMA and on individual sub-watersheds in the TCMA
indicates that about 70% of the road salt applied in the TCMA is not carried away by the Mississippi River. Rates
of seasonal road salt use are correlated with snowfall, road miles and population. Salinity in TCMA lakes increases
in winter and decreases in summer. Ionic composition of dissolved substances in lakes of the TCMA suggests
unnaturally high sodium and chloride concentrations compared to lakes and other water bodies in the Midwestern
U.S. Data indicate a rising trend in urban lake water salinity over the last 30 years. Shallow groundwater in the
TCMA, especially near major roadways, has started to show increasing chloride concentrations. Salinity trends in
lakes and shallow aquifers of the TCMA are of concern.
Stefan, Heinz G.; Novotny, Eric; Sander, Andrew; Mohseni, Omid.
Study of Environmental Effects of De-Icing Salt on Water Quality in the Twin Cities Metropolitan Area, Minnesota.
St. Anthony Falls Laboratory.
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