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<br />1786
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<br />Upper Basin
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<br />In the upper basin, historic mining of ore deposits has yielded large quantities of many valuable metals,
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<br />including copper, gold, iron, lead. silver, and zinc (Tweto, 1968). Water flowing through the abandoned mines and
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<br />mine tailings in the upper basin has contributed substantial quantities of the trace elements cadmium, copper, iron,
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<br />lead, manganese, and zinc to the Arkansas River (Moran and Wentz, 1974; Wentz, 1974). In this study, these six
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<br />trace elements were identified as the primary trace elements of potential concern in the upper Arkansas River
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<br />Basin. Samples analyzed for the primary trace elements were collected from the following main-stem sites: Lead-
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<br />ville, Malta, Granite, Buena Vista, Nathrop, Wellsville, Parkdale, and Portland (table I). Prior investigations have
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<br />indicated that concentrations of other trace elements in the upper basin, such as arsenic, chromium, mercury.
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<br />nickel, selenium, and silver are not elevated above analytical detection limits or were not considered to be constit-
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<br />uents of concern from a water-quality perspective. These six trace elements, collectively referred to as the second-
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<br />ary trace elements of potential concern, were sampled and analyzed at four selected sites five times during the study
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<br />period for the purpose of confirming that their concentrations were relatively insignificant from a water-qualiry
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<br />.'. perspective. Trace elements were analyzed in water samples that were collected from all of the major tributaries in
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<br />the upper basin. In this study, the major tnbutaries in the upper basin were defined as those tributaries that contrib-
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<br />ute at least five to ten percent of the annual flow in the upper Arkansas River or those that are known or suspected
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<br />to be substantial sources of some trace elements, primarily owing to localized land use in the tributary drainages.
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<br />16
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