Question c 42.Remberet al. (1993) measured the concentrations of 137Cs in the bo

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Question c 42.Remberet al. (1993) measured the concentrations of 137Cs in the bottom sediments of Medicine Lake, northern Idaho. Heavy-metal-laden tailings from the Coeur d?Alene mining district were deposited in this lake. Tailings were deposited during hoods as well?stratified. Heavy-metal. contaminated silts on the lake bottom. Atmospheric testing of nuclear bombs, the source of Cs, began in 1951 and reached a maximum in 1964. 137 Cs is first detected in the varved sediments at a depth of 30?32 cm and the 137 Cs maximum occurs at a depth of 16?18 cm. e. Tailings ponds were installed in the mining district in 1968 R. Have these ponds reduced the input of tailings to Medicine Lake? Explain.

Explanation / Answer

talings are mineral deposists in the lake , heavy metal laden tailings were deposited during floods are well stratified ,heavy metal ,contamined silts on the lake bottom . Cesium-137, an isotope produced in the atmosphere by nuclear bomb tests, was virtually absent in the environment prior to 1951, but reached its apex in 1964. Analysis of cesium-137 in the sediments of Medicine Lake revealed that 14 cm of fine-grained tailings were deposited in the lake from 1951 to 1964 and tailing deposition downstream was greatly reduced by the installation of tailings dams in the district in 1968. Cesium-137 analysis is accomplished by a fairly simple gamma-ray counting technique. The main source of the Cs137 contamination in CsI powder was water dissolved Cs137 used in the chemical process of cesium extraction at company side.

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