Radiochemical analyses of fission debris in the air along the 80th meridian, west

A number of radioisotopes formed in high yield by nuclear explosions have been determined quantitatively in the gross-fission-product conglomerate collected by air filters at sites along the 80th meridian during the IGY. Radiochemical analyses have shown that debris from two (or more) nuclear tests of the U.S. Hardtack Series in the Pacific crossed the equator. Save for the period of gross contamination in the troposphere by Hardtack debris, the average age of the fission-product conglomerate in the air has been consistently older in the southern than in the northern hemisphere. Furthermore, the Sr90 content of the air has shown a general pattern of maxima in the region between latitudes 20° and 40°N and between latitudes 20° and 40°S and a minimum in the equatorial region. During early 1958 the maximum in the north averaged about 7 times that in the south. The rapid spread of radioactivity from the Hardtack tests (identified by the presence of W185) and from Soviet nuclear tests emphasizes the fact that debris is not restricted to a narrow zone near the latitude of introduction.