Trace-metal concentrations in sediment and water and health of aquatic macroinvertebrate communities of streams near Park City, Summit County, Utah

The spatial distribution of metals in streambed sediment and surface water of Silver Creek, McLeod Creek, Kimball Creek, Spring Creek, and part of the Weber River, near Park City, Utah, was examined. From the mid-1800s through the 1970s, this region was extensively mined for silver and lead ores. Although some remediation has occurred, residual deposits of tailing wastes remain in place along large sections of Silver Creek. These tailings are the most likely source of metals to this system. Bed sediment samples were collected in 1998, 1999, and 2000 and analyzed using two extraction techniques: a total extraction that completely dissolves all forms of metals in minerals and trace elements associated with the sediment; and a weak-acid extraction that extracts the metals and trace elements that are only weakly adsorbed onto the sediment surface. This latter method is used to determine the more biologically relevant fraction of metal complexed onto the sediment. Water samples were collected in March and August 2000 and were analyzed for total and dissolved trace metals.

Concentrations of silver, cadmium, copper, lead, mercury, and zinc in the streambed sediment of Silver Creek greatly exceeded background concentrations. These metals also exceeded established aquatic life criteria at most sites. In the Weber River, downstream of the confluence with Silver Creek, concentrations of cadmium, lead, zinc, and total mercury in streambed sediment also exceeded aquatic life guidelines, however, concentrations of metals in streambed sediment of McLeod and Kimball Creeks were lower than Silver Creek. Water-column concentrations of zinc, total mercury, and methylmercury in Silver Creek were high relative to unimpacted sites, and exceeded water quality criteria for the protection of aquatic organisms. Qualitative measurements of the macroinvertebrate community in Silver Creek were compared to the spatial distribution of metals in streambed sediment. The data indicate that impairment related to metal concentration exists in Silver Creek.