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Show 24 Water Quality in the Great Salt Lake Basins, Utah, Idaho, and Wyoming, 1998- 2001 t£ T ' JF - Copper 10 20 30 2.0 20 40 60 50 100 150 0.5 1.0 1.5 2.0 CONCENTRATION, IN MICROGRAMS PER GRAM 1982 1963 1932 1902 1862 1723 Figure 40. Metals concentration in sediment core from Mirror Lake began increasing after about 1870. Due to the remote location and absence of mining in the watershed upstream from the lake, the metal enrichment is believed to be due to atmospheric deposition from mining- related activities. Data from Kada and others ( 1994, fig. 7). Trace elements in sediments exceed Probable Effect Concentrations only in areas with mining- related activities •••..•.•••.•..•:•••.-•,:•.•;•••---•••••::;•.•,-•.-;-•. activities, concentrations of trace elements in sediment often exceeded the Probable Effect Concentration ( PEC) values ( Waddell and Giddings, 2003). The PEC represents the concentration cDonald and others. 2000). The upper Weber River Basin, and the Utah Lake- Jordan River Basin were the most extensively mined areas and the Bear River Basin the least mined. The most heavily affected streams sampled were Little Cottonwood Creek. Concentrations at two sites on Silver Creek and at a site on the Weber River below the confluence with Silver Creek exceeded the PEC levels for arsenic, cadmium, copper, lead, mercury, silver, and zinc. Concentrations at two sites on Little Cottonwood Creek, as well as at a site on the Jordan River below the confluence with Little Cottonwood Creek. exceeded the PEC levels for arsenic, cadmium, copper, lead, silver, and zinc. In areas with very little mining, no PEC levels were exceeded. None of the concentrations in samples from the 15 sites sampled exceeded the PEC levels for chromium and nickel, and concentrations at only one site on Silver Creek exceeded the PEC for selenium. NAWQA samples represent the fine- grained fraction of bed sediment only ( less than 63 micrometers), which, in general, contains higher concentrations of trace elements than bulk sediment. The guidelines of MacDonald and others ( 2000) are intended for bulk sediment; thus, results from NAWQA samples may somewhat overstate the problem based on bulk- sediment criteria, and caution should be used in applying the criteria to values close to the PEC. 10,000 1.000 100 10 001 100.000 111 149128 33.0 ¥ 4 « * 8 1 • "| 4A8\ # 14 \ 1.06 Probable - Effect Concentration 459" I Jordan River Basin & s/ ssw* o* cr 1 From protocol lor aquatic hazard assessment ol selenium ( Lemly. 1995). - From Long and oth<? is. 1995 |
