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Ot1~~t:l~ . . Figs. 10 and 11 serve as an example of the trend of increasing mineral concentration in the downstream direction which was observed for each of the common minerals. The highest mean concentrations of common minerals were generally found in Yellow Creek, Little Beaver Creek, and Coal Creek (see Table 3). Yellow Creek contained mean concentrations of sodium in excess of the recommended criteria of 270 mg/l, which was sufficient sodium to produce Sodium Adsorption Ratios (SAR) of 17 during "high flow" and 15 during "low flow". Ratios of this magnitude indicate that the water may adversely affect sodium-sensitive plants if used for irrigation (NAS, 1972). . . Metals and ~e)ated Elements A total of 13 parameters were included in this grouping, and all results are discussed in terms of the total metal. Profiles for five of these metals (aluminum, copper, iron, manganese, and zinc) are shown in Figs. 12 through 16. The remaining metals were not profiled because they either exhibited little variation throughout the stream reach or they were present in concentrations below the analytical detection limit. The five "profiles", in combination with the metals data in Table 3, indicate significant variabilities in metal concentrations when comparing "low flow" measurements to "high flow" measurements. Mean concentrations of chromium, lead, and zinc were generally higher during "low flow", while concentrations of aluminum, cadmium, copper, and iron were generally higher during "high flow". Except for manganese, the remaining metals (arsenic, molybdenum, selenium, and silver) did not show appreciable differences in concentration between the "low flow" and "high flow" periods. Manganese concentrations averaged higher during "high flow" in the White River downstream from Meeker (see Fig. 15), but at other locations there was no apparent relationship between concentration and flow. Lithium concentrations measured during the two different flow periods could not be compared since the detection 1 imit was reduced from 25 jJg/l during the "low flow" study to 10 jJg/l during the "high flow" study. . . . ;. In order to evaluate the relative magnitude of the various metal concen- trations, the measured values have been compared to the recommended criteria and proposed standards shown in Table 4. It should be clearly understood that the numbers shown in Table 4 are not absolute" limits, but rather are intended to serve as "alert level" indicators. There clearly is a great need for additional metal toxicity research in order to fully justify specific numerical criteria and standards such as these. . The comparison of the metals data with the recommended criteria and proposed standards (criteria/standards) leads to several observations, as follows: . 1. The criteria/standard concentrations for several metals (aluminum, cadmium, lead, and silver) shown in Table 4 are below the detection limit achieved by EPA during one or both of the study periods. 30 . . L .h.. ;;, " ~:L:,