Molybdenosis in an Area Underlain by Uranium-bearing Lignites in the Northern Great Plains

Abstract

In the fall of 1975, cattle grazing to the north of an abandoned uranium mine on Flint Butte in Harding County, S. Dak., showed signs of molybdenosis, a disease due to molybdenum-induced copper deficiency. To identify the source of the problem, plant, water, and soil samples were collected on a grid design over a 16 km2 (~9 miles2) area around Flint Butte. Uranium, molybdenum, and copper concentrations were determined in western wheatgrass (Agropyron smithii) and sweetclover (Mililotus officinalis); molybdenum and copper concentrations and pH were determined in pond waters; and the pH of soils was determined. Ratios of copper to molybdenum in the forage were found to be below 2:1, the lowest value considered safe for cattle. Molybdenum concentrations in some surface waters were extremely high. These conditions are related to the outcrop of uranium- and molybdenum-bearing lignites at Flint Butte and in the nearby Flint Hills. Similar lignites are widespread, and it is likely that nutritional problems of the type encountered in the Flint Butte area exist in similar geologic terrain over a broad region of the northern Great Plains.