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<br />" " <br /> <br />4.3,1 EPA Water Quality Standards <br /> <br />0.14-4.60 mgll for non-salmonids. Toxicity of ammonia varies with temperature and pH (Valdez et al. <br />1993). <br /> <br />Dissolved Oxygen (DO) - The EP A criteria for non-saimonid fisheries for dissolved oxygen <br />is 6.5 mg/l for early life stages and 6.0 mgll for all other life stages. The criteria forsaimonid fisheries is <br />11 mgll for early life stages and 8 mgll for other life stages. <br /> <br />Nitrate- NoEPA criteria exist for nitrate. Westin (1974) found the 7-day LCso for fmgerling <br />rainbow trout (Oncorhynchus mykiss) to be 1060 mgll.Nitrate nitrogen levels at or below 90 mgll have <br />been found not to adversely affect warmwater fish (Valdez et al. 1992). <br /> <br />pH - The European Inland Fisheries Advisory Commission (1969) determined that a pH of 5-9 <br />was not directly lethal to freshwater fish. However, the toxicity of several common pollutants is markedly <br />affected by pH changes within this range (Valdez et al. 1992). The EP A criterion for freshwater aquatic <br />life is 6.5-9.0. <br /> <br />Phosphate - No EP A criteria exist for phosphate. In general, phosphate is an indicator of <br />pollution but is not considered a pollutant itself except for its effect on plant growth (Toole 1992). <br /> <br />Sulfates - No EP A criteria exist for sulfates. <br /> <br />Total suspended solids (TSS) and settleable solids - The EP A states that settleable and <br />suspended solids should not reduce the depth of the compensation point for photosynthetic activity by more <br />than 10% from the seasonally established norm for aquatic life. <br /> <br />Total dissolved solids (TDS) - The EP A reports that, in general, water systems with TDS levels <br />in excess of 15,000 mgll are unsuitable for most freshwater fish; however, the EP A has set no criteria for <br />TDS. In experiments several common freshwater species have survived exposure to 10,000 mgll TDS <br />(Valdez et al. 1992). Pimentel and Bulkley (1983) found that Colorado squawfish avoided TDS <br />concentrations greater than 4,000 mgll. <br /> <br />Aluminum - No EP A criteria exist for aluminum. <br /> <br />Arsenic - The EP A states that freshwater organisms should not be affected unacceptably if the <br />4-day average concentration of arsenic (1II) does not exceed 190 /-IgIl more than once every three years on <br />average and if the I-hour average concentration does not exceed 360 /-IgIl more than once every three years <br />on average. Inorganic arsenic (IV) is acutely toxic to freshwater animals at concentrations as low as 850 <br />/-Ig/l. For inorganic arsenic, an acute:chronic ratio of 28 has been obtained for fathead minnow <br />(Pimephales promelas). <br /> <br />Cadmium - Cadmium toxicity is affected by water hardness. The EP A states that, except where <br />a locally important species is very sensitive, freshwater aquatic organisms should not be affected <br />unacceptably if the 4-day average concentration of cadmium (in /-IgIl) does not exceed the numerical value <br />given by e(O.7852[1n(hm-dn."l-,,490) more than once every three years on the average and if the I-hour average <br />concentration (in /-IgIl) does not exceed the numerical value given by e(I.I2811n(h-'''~'.82$) more than once <br />every three years on the average. <br /> <br />Copper - Copper toxicity is affected by water hardness. The EP A states that, except where a <br />locally important species is very sensitive, freshwater aquatic organisms should not be affected <br />unacceptably if the 4-day average concentration of copper (in /-Ig/I) does not exceed the numerical value <br /> <br />20 <br />