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

The Utah Division of Water Quality (UDWQ) lists Little Cottonwood Creek (LLC), Salt Lake County, Utah, as impaired by dissolved zinc, cadmium, and copper. A legacy of mining in the area has left mine dumps and drain tunnels, the most probable sources of the heavy metals. A 1998 survey by the USGS found copper concentrations downstream of the White Pine Creek confluence to exceed water quality criteria for dissolved copper. In 2001, the Tanners Flat Campground and Red Pine Creek area contained high levels of dissolved copper and zinc. A 2002, UDWQ report found White Pine Creek to be a significant source of copper. Stream sediments taken near the Red Pine Creek confluence by Hannah Finley, a student at Salt Lake Community College, contained cadmium. This study aims to determine the extent to which Red and White Pine Creeks are contributing to heavy metals in LCC. Samples were taken from 10 locations, 8 along LCC and one from Red and White Pine Creeks. Samples were tested for heavy metals which generally decrease downstream due to attenuation but increases in concentrations were present near the White Pine confluence, Tanner’s Flat Campground, and near the Little Cottonwood Creek Bridge. Copper concentrations were highest in White Pine Creek at 19.1 ppb, downstream of the confluence LCC concentrations increased from 5.6 to 6.4 ppb. Copper concentrations increased in LCC adjacent to Tanners Flat Campground from 6.4 to 9.8 ppb. Red Pine Creek had copper concentrations of 0.8 ppb, downstream of the confluence concentrations in LCC decreased from 9.8 to 5.3 ppb. Further downstream adjacent to Little Cottonwood Bridge copper increased from 5.3 to 8.4 ppb. The highest concentrations of cadmium, 0.98 ppb, and zinc, 120 ppb, were found in samples upstream from the White and Red Pine confluences. There are slight increases in the zinc concentrations, 100 ppb to 102 ppb, and cadmium, 0.91 ppb to 0.93 ppb, immediately downstream of the White Pine Creek confluence. Zinc and cadmium levels decrease downstream with no further increases. This suggests that White Pine Creek is a likely source of copper, zinc, and cadmium to LCC and that Red Pine Creek is not a likely source of these metals. Further sampling will be done to ascertain the sources of impairment with more precision, especially near the Little Cottonwood Bridge to investigate the increase in copper.