GRAZING STUDIES ON A CONTAMINATED RANGE OF THE NEVADA TEST SITE D. D. Smith Environmental Protection Agency Environmental Monitoring and Support Laboratory, Las Vegas ABSTRACT Actinide data from gonad, muscle, liver, lung, and femur samples collected from five cattle (three aged cows and two yearling bulls) that grazed a plutonium-contaminated range on the Nevada Test Site are discussed. Comparisons are made with data from similar tissues collected from a group of cattle that grazed in the area of the Rocky Flats Plant in Jefferson County, Colorado. Plutonium-239 levels in the gonads from both groups were higher than those reported for muscle. The medium plutonium-239 value from the gonads of the Nevada Test Site cattle was 25 times higher than the muscle, approximately equal to the femur, and one-half to one-third of the liver and lungs. Uranium levels in the gonads of both groups of cattle were greater than in all of the other tissues discussed. Little difference was noted in the activity levels in the gonads of the males versus the females. An estimate of soil ingestion by grazing cattle was made by weighing the sediment from washed ingesta collected from fistulated steers that had grazed for a 24-hr period on both ungrazed range and heavily grazed range. Sediment was also collected from the entire gastrointestinal tract of a sacrificed cow. It was estimated that less than 0.5 kilograms of soil would be ingested for a 24-hr period by cattle grazing this range. INTRODUCTION A grazing study on the plutonium-contaminated range of Area 13 of the Nevada Test Site was initiated in May, 1973 and is continuing. The objectives, protocol, sampling, and analytical methods used in this study were previously described (Smith, 1974, 1975, 1976). These reports included data on the botanical composition of rumen ingesta collected from both sacrificed animals and rumen-fistulated steers. 139