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Show Table 4. The minor trace metals In GSL brines which are included in the DWQ's ( June 9 and 22, 1994) Lab Analysis Reports. Metal SiteAS2 ( south arm) SiteLVG4 ( north arm) Arsenic 130 218 Cadmium < 3.0 < 11 Chromium < 5 < 5 Iron < 220 < 220 Silver < 2 < 2 Zinc < 330 360 Mercury <. 2 <. 2 Barium 180 170 Copper < 220 < 220 Lead < 30 < 12 Manganese < 55 < 55 Selenium < 12 31 (< = less than) It has been postulated that the absolute quantities of the ions of magnesium, potassium, calcium and sulfates in lake brines is decreasing relative to sodium and chloride. Data collected by UGS since 1966 show a slight decline in the yearly average, south- arm dry weight percentages of magnesium, potassium, calcium and sulfates over time, while sodium and chloride show a slight increase ( Gwynn, Work in Progress). During the low surface- elevation stages of the lake, from 1935 to 1945 and from 1959 to the mid- 1960s, sodium chloride precipitated in the main body of the lake and in Gunnison Bay ( the south and north arms). Madison ( 1970) states that salt precipitated at lake elevations below 4195 feet and Whelan ( 1973) reports that some 1.21 billion metric tons of sodium chloride precipitated throughout the lake at those low elevations. While the precipitated salt in the south arm had redissolved by mid- 1972, it took until about 1986 before all the salt in the north arm had been redissolved ( Wold et al., 1996). In 1992, salt again began to precipitate on the floor of the north arm during the summer months, and it is believed that precipitation continued through 1997. Dry- weight percentages of magnesium, potassium and calcium were increased during historic low lake levels because sodium chloride is the first salt to precipitate as the concentration of lake brine increases. Conversely, the concentrations of magnesium, potassium and calcium are believed to be recently decreasing relative to sodium because of 50 |