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Cosmic ray produced beryllium-7 in the atmosphere

Thesis/Dissertation ·
OSTI ID:5970213
The concentrations of cosmic ray produced /sup 7/Be in a total of 137 individual samples of rain and snow falling at Fayetteville (36/sup 0/N, 94/sup 0/W), Arkansas, were measured during the period between September 1979 and December 1981. In general, higher activities were observed during the spring months. This suggests that the /sup 7/Be, which was originally located in the lower stratosphere, fell into the troposphere during the spring and then carried down to the earth's surface by rain scavenging. This seems to be attributable to the tropopause folding events which are the dominant stratospheric/tropospheric exchange mechanism. A comparative study of the seasonal variations of cosmogenic /sup 7/Be, radon daughter /sup 210/Pb, fission product /sup 90/Sr and /sup 234/U and /sup 235/U were carried out. After the 25th Chinese test (October 16, 1980), the concentration of /sup 7/Be did not change, whereas /sup 90/Sr increased. This is consistent with the conclusion that the main part of /sup 7/Be in the atmosphere is cosmogenic in origin. The concentration of /sup 7/Be and /sup 32/P were measured in a total of 23 rain samples, during the period between March and June, 1981. The mean tropospheric residence time was estimated from the mean /sup 7/Be//sup 32/P activity ratio. The results of this study were compared with previous measurements of the mean tropospheric aerosol residence times at different latitudes. The agreement is generally good.
Research Organization:
Arkansas Univ., Fayetteville (USA)
OSTI ID:
5970213
Country of Publication:
United States
Language:
English