THE IMPACTS OF DEICING AGENTS ON THE WATER CHEMISTRY OF WETLANDS ADJACENT TO ROADS IN FOUR MID-MICHIGAN COUNTIES

Highway runoff during snowmelt has been shown to increase the amount of dissolved ions in aquatic systems adjacent to roads because of deicing agents. Few studies, however, have addressed the impact that road salt may have on ephemeral wetlands. As part of an interdisciplinary study on the impacts of road salt on amphibians, nine wetlands in close proximity to roads were monitored for the presence of major cations and anions indicative of deicing agents during a period of six months. The three main objectives that we addressed were to 1) compare ion concentrations in sites along side roads receiving salt (from the Michigan Department of Transportation) with control sites; 2) contrast the concentration of chloride at three distances from the road within sites; and 3) monitor how ion concentrations changed temporally at each location by collecting snow and water samples from February until July, 2004. Analyses were conducted using ion chromatography (IC). Cations measured included Li,Na, NH₄,K,Mg,and Ca. Anions included F,Cl, NO₃,Br,PO₄,and SO₄. To check the completeness of the analyses, we have plotted the total cation equivalents vs. total anion equivalents. Water analyses appear to be almost complete, while the snow may have contained CO3/HCO3 or OH anions, which cannot be analyzed by IC. Total dissolved solids were higher in wetlands adjacent to roads receiving salt with a range of 1.2 to 4937.8 ppm and a mean of 366.6 ppm, compared to a range of 16.6 to 390.7 ppm and a mean of 88.0 ppm in wetlands not exposed to salt. In particular, salted sites contained higher levels of Na, Cl, Mg, and SO₄. Chloride was significantly higher in samples collected at the point nearest to the road versus an intermediate and a far point in salted sites (Kruskall-Wallis test, p=0.000). There was no significant variation in chloride within unsalted locations (p=0.416). Ionic concentration remained elevated in three of the five salted sites up until the last sampling date. Results suggest that runoff containing road salt has a significant effect on the ionic concentrations of wetlands adjacent to roads, approaching lethal values experimentally determined for hatching tadpoles. In addition, since values remained elevated for nearly five months, there may be negative impacts on other species utilizing these wetlands.