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Technical Report

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impoundments, trace metals, water quality, reservoirs


An investigation of the trace element content of two impoundments on the Ouachita River, Arkansas, was conducted. Common water quality parameters were followed in the reservoirs in an effort to determine the factors which were influencing the trace element concentration. The following trace metals were determined in both the particulate phase (retained by a 0.45 micron filter) and the soluble phase (passed by a 0.45 micron filter): iron, manganese, copper, cobalt, nickel, lead, chromium, and zinc. These measurements were made periodically for one and a half years. Results indicate that the chemical regime of the impoundments which were studied was greatly influenced by the cool water releases from an upstream impoundment. A cold density current throughout the entire main stem of the reservoir furnished dissolved oxygen to the lower portion . of the impoundments and prevented the accumulation of large quantities of iron and manganese. More typical hypolimnic conditions were observed in the sidepockets of the reservoir. Data suggest that outside of hypolimnic zones in the reservoir, soluble iron is present in very small quantities, usually less than 10 ppb.

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