Gamma emmitters on micro-becquerel activity level in air at Kroków (Poland)

Grabowska, S., Mietelski, J.W., Kozak, Krzysztof and Gaca, P. (2003) Gamma emmitters on micro-becquerel activity level in air at Kroków (Poland). Journal of Atmospheric Chemistry, 46 (2), 103-116. (doi:10.1023/A:1026067614448).

Abstract

The Petryanov air filters combined into half-year sets were analyzed for the presence of 40K, 137Cs and 22Na by means of low-background gamma rays spectrometry. Each sample contains aerosols from more than 1 Mm3 of air. Samples were collected in ground level air at Kraków (Southern Poland) from 1996 to 2002. Activity concentrations of 40K are almost constant with the mean of 14.7± 4.5 μ Bq m−3. Activity concentrations of 137Cs, which are on the level of single μ Bq m− 3 show exponential decrease with effective half-life time of 7.07± 0.77 years. The cosmogenic 22Na shows a strong seasonal variation with significant different mean values activity concentration between 0.333± 0.095 μ Bq m−3 and 0.137± 0.045 μ Bq m−3, for summer and winter, respectively. Moreover, the activity ratio for two cosmogenic radionuclides: 22Na and measured previously 7Be show also changes with statistically significant seasonal differences. The lower values were found during winters. The mechanisms which might govern this ratio are discussed. The conclusion is that transport of 22Na during summer seems to be so much effective, that results in kind of relative depletion of stratosphere of this nuclide.

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