SOURCE TRACKING OF INORGANIC CHEMICAL CONTAMINANTS IN MILLERS CREEK, ANN ARBOR

Millers Creek drains only 2.4 square miles of the Huron River Watershed in Ann Arbor, but is 80% urbanized. The pollutants from this urbanized creekshed eventually make their way into the Huron River and impact downstream areas. Previous research of Millers Creek revealed elevated concentrations of inorganic contaminants that have negative impacts on the ecosystem. Specifically, testing along Millers Creek has revealed elevated chloride concentrations above the EPA standard of 250 mg/L. Previously, the Huron River Watershed Council collected samples from April to September, which showed elevated chloride levels in the summer. Elevated chloride levels in the summer indicate an additional source other than road salt. The goal of this current research project is to locate the most likely source of chloride contamination in the creek.

This project included collecting water samples from multiple sites along Millers Creek biweekly for 12 months in order to compare the temporal trend with watersheds known to be contaminated with road salt set in similar ecosystems. The samples collected were also compared spatially to find the most likely area of contamination. Samples were tested in the field with a handheld pH/Conductivity/Temperature meter and then collected. The samples were then analyzed in the laboratory for several inorganic constituents including nitrate, sulfate, and phosphate along with turbidity. Comparison of electrical conductivity and chloride concentrations revealed a strong correlation, indicating chloride as the primary contaminant in the creek. Temporal trends follow the same trend compared to other similar ecosystems in which the summer months have a lower concentration of chloride, but Millers Creeks averages are still high. Spatial trends indicate a source at the headwaters of the creek on the eastern branch. Further research is to be done on the western branch. Temporal trends indicate road salt as the primary source in the winter months, but due to higher than normal averages in the summer there is most likely another source of contamination. Further research is needed to pinpoint the exact location and source of the chloride contamination.