Application of krypton-85 in groundwater dating

The method for determination 85Kr activity in groundwater and its application in isotope hydrology is presented. Various aspects of 85Kr presence in the earth's ecosphere are discussed in the first part of the paper. The method for 85Kr activity measurement in groundwater is presented in the second part of the paper. Analytical procedure consists of the following steps: extraction of the gases dissolved in water sample, separation of the Ar+Kr mixture from the gases, 85Kr activity measurement in miniature proportional counter, mass spectrometry determination of the krypton gas volume in the proportional counter. About 7 days is necessary for complete analysis of one sample - the error of analysis not exceeds 10 per cent. The results of 85Kr activity measurements (together with tritium and carbon 14C determinations) in 14 different water samples allowed to verify usefulness of 85Kr dating of young water. (author)