Study of radioactive isotopes of beryllium, polonium, uranium, and plutonium in the atmosphere

Radiochemical measurements were carried out for /sup 239.240/Pu in a total of 94 rain and snow samples collected at Fayetteville (360 N, 940W), Arkansas, during the period between May 1983 and November 1985. The concentrations of 7Be in most of these samples were also measured and these results were compared with previous samples. Average concentrations of cosmic-ray-produced radionuclide 7Be in rain remained fairly constant year after year. The annual rate of 7Be deposition at Fayetteville, Arkansas, was calculated from these data to be 5.2 dpm/cm2/year, which corresponds to a value of 2.8 x 10-2 atoms/cm2/second for the 7Be production rate in the atmosphere. The concentrations of bomb-produced radionuclides such as 89Sr, 90Sr and /sup 239.240/Pu in rain have drastically decreased since the last nuclear test explosion was conducted by the government of People's Republic of China in 1980. The concentrations of uranium isotopes and radon daughters in rain, on the other hand, were found to be affected by atmospheric injections of volcanic ashes from the 1980 eruption of Mount St. Helens and the 1982 eruption of El Chichon volcano in Mexico. Moreover, the burnups of the nuclear-powered Soviet satellites have caused marked increases in the levels of 235U and 234U in some of the rain samples. A sharp increase in the 210Po/7Be ratio in rain samples collected toward the end of 1980 and the beginning of 1981 was attributed to an atmospheric injection of 210Po from a series of major eruptions of Mount St. Helens