Measurements of the Air Concentration of Gross Fission Product Radioactivity during the IGY July 1957–December 1958

Measurements of the gross fission product radioactivity in the air at 21 sites along the 80th meridian 2nd 4 sites in the North Pacific area are reported for the period July 1957–December 1958. The activity levels at the various sites are related both to the stratospheric deposition of nuclear debris and to the direct introduction of radioactive material into the troposphere upwind of the collecting sites.

Radioactive debris injected into the troposphere at any particular site spreads rather rapidly throughout the same hemisphere but rarely crosses the equator in any quantity. An exception to this occurred during the Hardtack series in the Pacific when massive quantities of activity were transported to the Southern Hemisphere by winds in the upper troposphere.

It is again shown that periods of heavy rainfall, such as occur during the rainy season in Panama, cause a general decrease in the concentration of fission products in the air.