TEMPORAL AND SPATIAL ANALYSIS OF DISSOLVED CADMIUM, COPPER, AND ZINC IN THE IMPAIRED LITTLE COTTONWOOD CREEK, UTAH

Upper Little Cottonwood Creek (LCC), Central Wasatch Range, Utah, has many historic mine dumps and drain tunnels with high concentrations of heavy metals such as zinc, copper, and cadmium in soil and water. In 2016, the Utah Department of Water Quality (UDWQ) identified LCC as impaired by zinc, copper, and cadmium but don’t know the origin of the heavy metals. The purpose of this study is to identify the source of water-based impairments for zinc, copper, and cadmium. This study analyzed existing water quality and heavy metal concentrations from the UDWQ from 2008 to 2016 and new water samples collected in the summer 2019 for dissolved heavy metals. The UDWQ water data from 4 locations in the canyon show zinc, copper, and cadmium increasing upstream closer to the areas with mine dumps and drain tunnels. At the upper part of the canyon, zinc, copper, and cadmium vary seasonally, with the highest concentrations are in the late summer when discharge is low. Water samples from mine drain tunnels have the highest concentrations of zinc, copper, and cadmium during all months. This suggests the source of dissolved metals is from groundwater intrusion or mine drain tunnels at this location. Midway up the canyon, zinc and cadmium concentrations are highest during low discharge summer and winter months while copper is opposite with highest concentrations during high discharge spring runoff. This suggests the source of dissolved metals is surface runoff in the winter and groundwater or mine drain tunnel intrusions in the summer at this location. Concentrations of copper from the mouth of the creek to midway up the canyon, peak during high-discharge spring runoff, suggesting a different source for copper. To better understand seasonal and geographic changes of zinc, copper, and cadmium concentrations, this study will collect forty-four water samples from 11 locations over four months to be analyzed for dissolved metals, pH, temperature, and oxidation-reduction potential changes during the summer of 2019.