RADIOCESIUM AND PLUTONIUM - STILL TOGETHER IN BACKGROUND SOILS AFTER MORE THAN 30 YEARS

Soil samples were collected from sites near Denver, Colorado, in the s ummer of 1994 as part of the Rocky mats Plant ''Background Soils Chara cterization Program.'' Analysis of the soils for plutonium and radioce sium give a mean activity ratio of radiocesium to plutonium of 38 +/- 4 (as of 1 July 1994). This ratio strongly suggests that these soils r eceived their plutonium and radiocesium from world-wide fallout from t he testing of nuclear weapons, over 30 years ago, and that these two c hemically different elements are still fixed together in the sampled s oils in the same ratio as in soils analyzed over 20 years ago. Thus, t he radiocesium/plutonium activity ratio in background soils is predict able and deviations may indicate contamination with radiocesium and/or plutonium from a source other than weapons fallout. Copyright (C) 199 6 Elsevier Science Ltd