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Analysis of Trace Element DaTa - Unless otherwise noted, the chemical <br /> analysis determined the total concentrations of each species. Nitric acid was added <br /> To unfiltered samples in those cases in which the total concentrotions were to be <br /> deterimined. Sulfuric acid was used as a preservative in those samples for which <br /> ammonia and nitrate were to be determined. Determination of ortho-phosphate and <br /> dissolved iron require filtering in the field. In August 1980, it was discovered that <br /> proper filtering was not taking place, and procedures were corrected immediately. <br /> Only the concentrations of ortho-phosphate and dissolved iron should be affected. <br /> Proper filtering was conducted beginning with September 1980 samples. <br /> As a means of assessing the significance of the trace element data, <br /> concentrations of individual species measured in grab samples from Trout Creek and <br /> Oak Creek are compared with corresponding criteria recommended by the National <br /> Academies of Science and Engineering. This comparison is shown in Tables 2.5-10 <br /> and 2.5-II. The criteria listed in this table are The most restrictive ones <br /> recommended and some are based upon toxicity to humans, toxicity to marine life, <br /> or sim ply upon such factors as taste. <br /> Examination of the column containing the number of times the criteria was <br /> exceeded at each of The Trout Creek stations provides the best overall view of the <br />• trace element data. It is observed that manganese and dissolved iron are the only <br /> species whose concentration exceeded the criteria frequently. I1 is especially <br /> important to note that the rate of exceedancy at TRA is about the same as for the <br /> downstream stations. This implies that the runoff from the mined land that enters <br /> the stream below TRA does not increase The in-stream concentration of manganese <br /> and dissolved iron appreciably. This statement holds for the other trace elements, <br /> also. <br /> An evaluation of the statistical significance of the difference between the <br /> means was conducted for selected parameters to further substantiate the above <br /> observation. Atwo-sample "t" test using Fisher "T" distribution was utilized: <br />n I + I I /2 <br />w~l ~~l ~- <br />where x and y = the means in each data set <br />a w = pooled standard deviation <br />Revised 7-81 2.5-39 <br />