ABSTRACT

The amount of excess ²¹⁰Po activity injected into the atmosphere by the 18 May 1980 eruption of Mount St. Helens was greater than that of ⁹⁰Sr released by the 16 October 1980 Chinese test explosion of a 0.2 to 1 megaton nuclear device. The occurrence of a ‘mystery’ cloud prior to the 28 March 1982 eruption of El Chichón volcano was accompanied by an increase in the ²¹⁰Po/²¹⁰Pb ratio in rain samples collected at Fayetteville, Arkansas, during the months of January and February, 1982.