The distribution of tritium fallout in precipitation over North America

In 1958 the U.S. Geological Survey and the U.S. Weather Bureau jointly conducted a study of tritium fallout distribution over the continental United States, Alaska, and Puerto Rico. The observation period extended from early April to late July in most areas. While this was insufficient to cover the decay side of the curve, it was sufficiently long to establish general trends of tritium activity contours. Tritium activities were found to be maximum in the north central part of the country and minimum in coastal areas. The tritium activities show an inverse correlation with chloride concentrations in precipitation. Tritium activities in precipitation appear to be influenced by several “low altitude effects” particularly in storms of brief duration. Ground level tritium activity measurements are not directly representative of tritium in cloud moisture because of these effects.