Summary Report of the Grazing Studies Conducted on a Plutonium-Contaminated Range in Area 13 of the Nevada Test Site

摘要

Actinide concentrations in the tissues of beef animals periodically sacrificed and sampled during a 3-year grazing study on a plutonium-contaminated range of the Nevada Test Site are tabulated and discussed. The primary objective of this study was to determine the uptake and tissue distribution of the plutonium by ruminants. Food habit analyses of ingesta from rumen-fistulated steers and sacrificed cattle revealed that shrub species made up the major portion of their diet during most seasons of the year. Grasses were preferred during the spring months. Using activity levels found in the rumen contents, it was estimated that a study cow ingested 100 microcuries of plutonium-239 prior to sacrifice. Of this, 16.4 microcuries was in rumen fluids from which a combined retention factor of 0.0034% was calculated for the bone, muscle, and liver. Comparisons of plutonium-239/plutonium-238 ratios in ingesta and tissues indicate that the plutonium-238 is more readily absorbed and retained. No radiologically significant lesions were found. The gonadal concentrations of the actinides were significantly higher than those of blood and muscle and approached those of bone. These data indicate that consideration should be given to the plutonium-239 dose to gonads as well as that to bone, liver, and lungs of man. Actinide concentrations of animals born in the study areas showed an increasing trend with time. Concentrations of plutonium-239 in the lung, liver, muscle, and femur tissues of the Area 13 cattle were significantly higher than in tissues collected from grazing cattle from other sites. The plutonium-239 concentrations in bones, lungs, and livers collected from wildlife with free access to and from the contaminated zones reflect the dilution resulting from these animals ranging into the less contaminated areas around the study sites. (ERA citation 04:047417)