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

Millers Creek is a highly urbanized tributary surrounded by impervious surfaces, residencies, and businesses which drains 2.4 miles of the Huron River Watershed in Ann Arbor. Contaminants from the creekshed flow directly into the Huron River and impact downstream areas. Previous investigations of spatial and temporal trends revealed elevated concentrations of inorganic constituents in the creek. More specifically, research showed chloride levels throughout the year being above the EPA standard of 250 mg/L. In addition to this outgoing undergraduate research project, the Huron River Watershed Council collected samples in summer of 2019 which revealed elevated chloride levels. High concentrations of chloride in the summer indicate sources other than road salt.

The primary goal of this project is to determine the primary source(s) of chloride in the creek. Currently, students have continued collecting surface water samples from multiple sites along Millers Creek biweekly to compare temporal and spatial trends. In the field, samples are tested with a handheld pH/Conductivity/Temperature meter; once in the lab, samples were analyzed for inorganic constituents including iron, manganese, and chloride along with turbidity. Comparison of electrical conductivity and chloride concentrations indicate chloride as the main contaminant of the creek. Although temporal trends indicate road salt as the primary source in the winter months, due to higher than normal chloride concentrations in the summer, there are likely other sources of contamination. The next phase of the project involved installing 2-inch diameter wells 10ft below the ground surface adjacent to the creek allowing comparison between surface and groundwater trends which may help narrow down the source of contamination.