Radionuciide concentrations for 89Sr, 90Sr, 144Ce, and 137Cs were sequentially sampled from two rainstorms to study fallout behavior as a function of rainfall rate and type of storm approximately 7 months after the eighth Chinese nuclear explosion of December 27, 1968. Great time variability in the 89Sr/90Sr ratio was found in conjunction with a well‐developed storm on July 21, but a nearly steady ratio was observed in a stratified stable‐type storm on August 14. Tapping of stratospheric air appeared to be the cause of the ratio changes. For both storms, a strong trend was found for concentrations of radioisotopes to decrease with increase in rainfall rate. Detailed discussions on meteorological factors, including a dilution effect, are given to interpret the experimental data.
Three Chinese thermonuclear weapons tests were the major sources of nuclear debris in the Northern Hemisphere from late 1968 through mid-1970. Isotopic ratios of debris from each of these tests varied with time in a similar manner. After a sharp initial peak, the agSr/90Sr ratios showed a less zig-zag pattern and increased slowly for several months after each nuclear test. Radioactive debris was detected from a French nuclear test series conducted in the Southern Hemisphere during the summer months of 1970. Interhemispheric transit times were between 1 and 2 months. French debris may have crossed the Equator uiu Hadley Cell Circulation.
Strontium 89 and 90 were measured in rain water and air at Fayetteville, Arkansas (36øN, 94øW), for 9 months after the ninth Chinese atmospheric nuclear test. The s•Sr?øSr activity ratios showed behavior very similar to the pattern of variation observed after the eighth Chinese atmospheric test. Ratios of •Sr or •øSr activity in rains to activity in air samples were coniputed, and these scavenging ratios were found to vary widely, but those for •Sr tended to be higher than those for •øSr. These ratios did not have a welldefined relationship with time, amount of rainfall, or a number of meteorological parameters. The data, however, indicate that a consistent relationship between fallout and rainfall may be necessary for scavenging ratios to be meaningful and useful on a short-term basis. This relationship apparently does not exist in areas of high cumulative deposition of 9øSr, such as Fayetteville. E•gelmann [1970] has recently calculated the ratio of radioactive isotopes in rain and air samples (the so-called scavenging ratios) from a variety of sources and conditions. He recom-mended that these ratios be measured in the future, since such data may contribute to the understanding of precipitation processes and weather modification. Little is known concerning the relationship between the scavenging ratios and meteorological parameters, because of the difficulties involved in measuring the concentrations of radioactive isotopes in rain and in air simultaneously [e.g., Junge; 1963]. Shimo• [1970] reported that the monthly fl radioactivity from wet fallout in Budapest, when it was plotted against total precipitation for the month, gave two smooth curves if the yearly activity data were divided into summer and winter months. Gedeonov et al. [1970] found a simple proportionality between the concentrations of fission products in rain and air in Leningrad. These results seemed to indicate that relationships between the scavenging ratios and meteorological parameters could be established, once a sufficient amount'of data became available. In the present study the concentrations of 8øSr and øøSr were measured in rain and air samples collected at Fayetteville, Arkansas, for a period of 9 months following the ninth Chinese atmospheric nuclear explosion of September 29, 1969. EXPERIMENTAL TECI-I NIQUE Air samples were collected on the roof of the chemistry building at (he Universi(y of Arkansas by a Gelman 'Hurricane' air sampler, model 16003, which collected 140 m 3 of air per hour. Air was sampled for 1-or 2-day periods wi(h the use of cellulose-(ype IPC 1478 filters. The filters were relatively porous, and the flow ra(e did not drop by more (han • few percent during the collection period. Rain samples were ob-(ained from five co]lec(ors each 9.0 m • in area also located on the roof of (he chemistry building. Strontium was separa(ed from other fission produc(s as (he nitrate and radiochemically purified by the me(hod of Hodges [1963] with the addition of a calcium removal s(ep. The separ,•-(ion of s(romium from calcium w...
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