Magnesium-28 in rain: produced by cosmic rays.

Existence of magnesium-28 (half-life, 21.3 hours) produced by cosmic rays in rain at concentrations of 1.7 and 6.1 x 10(-1) atoms per milliliter was established radiochemically by isolating this nuclide from several hundred liters of rain samples collected at Fayetteville, Arkansas.

Single fallout particles and zirconium-95 from the Chinese nuclear explosion of 9 May 1966.

Daily fluctuations of the number of single fallout particles and activity of zirconium-95 in the groundlevel air were measured at Fayetteville (94 degrees W, 36 degrees N), Arkansas, for a period of about 3 months after the Chinese nuclear explosion of 9 May 1966. We found a cyclic pattern of variations for both zirconium-95 and fallout particles; this indicated that they were airborne for a long period and traveled far. Apparently, some of the particles circled the world more than once.

Fallout from the Chinese nuclear explosion of 17 June 1967.

Low-level activities of iodine-131, barium-140, and strontium-89 were found in a series of rain samples collected at Fayetteville, Arkansas, during the period from late June through August 1967. The ratios of these short-lived isotopes to strontium-90 were determined as accurately as possible. The data indicate that the debris from the Chinese nuclear explosion was injected primarily into the stratosphere.

Mass-yield distribution of the fission products in fallout from the 14 may 1965 nuclear explosion.

Twenty single particles separated from a 20-liter sample of rain collected in Osaka, Japan, shortly after the 14 May 1965 test explosion of the Chinese nuclear device, were analyzed radiochemically. The abundance pattern of the fission products in these particles resembled the shape of the mass-yield curve for the thermal neutron-induced fission of uranium-235, except for the facts that cesium-hl37 and strontium-90 were markedly depleted and the yields near the symmetric fission region appeared to be somewhat enhanced.

Deposition of excess amount of natural U from the atmosphere.

The concentration of 238U in rain and snow collected at Fayetteville (36 degrees N, 94 degrees W), AR, showed a marked increase during the summer months of 1980; and also during spring 1981, while Mount St. Helens remained active. This observed increase of 238U was due to the fallout of natural U from the eruption of Mount St. Helens. Based on the results from the analysis of rain and snow samples for the period March 1980-October 1982, the amount of 238U brought down by the rain is estimated to be 6.55 X 10(3) Ci.