Plutonium anomalies in attic dust and soils at locations surrounding the Nevada Test Site.

Attic dust and soil samples were collected during the Summer of 1996 and the Spring of 1997 in southern Nevada and southern Utah. Analysis of the samples for radiocesium and plutonium give activity ratios of radiocesium/plutonium that range from 0.7 +/- 0.1 to 27 +/- 2, well below the world-wide fallout ratio of 34 +/- 4 (as of 1 July 1997). This indicates anomalous plutonium throughout the region, including areas to the south of the Nevada Test Site (NTS), generally believed to have received only world-wide fallout. Safety tests and above-ground detonations that resulted in incomplete fission, conducted at the NTS during the 1950's and 1960's, are likely sources of this excess plutonium.