Issue 7, 2008

Return period of enhanced gamma ray dose rates: regional differences observed in Japan

Abstract

We estimated the return period of an increased gamma ray dose rate (Δγ) derived from 222Rn progeny deposited with precipitation. The approximate probability distribution for Δγ followed a Hazen plot, which is an empirical plotting equation, indicating that the distribution of Δγ was approximated by a nearly double-exponential. The distribution of Δγ was well represented by the Gumbel distribution, and the return period for Δγ was estimated theoretically. There was a notable regional difference in the return period between the coast of the Japan Sea and the inland or Pacific coast areas: the return period for a given Δγ at monitoring sites on the Sea of Japan coast was 1.5 to 2.5 times shorter than that in the inland or Pacific coast areas. This variation with locality suggests that the rate of wet-deposition of 222Rn progeny is larger at sites on the Sea of Japan coast than inland or on the Pacific coast areas. The expected return period for the maximum Δγ at each site was about 10 years. This estimation of the return period of Δγ is a novel approach to the study of environmental science in fields such as radioactivity.

Graphical abstract: Return period of enhanced gamma ray dose rates: regional differences observed in Japan

Article information

Article type
Paper
Submitted
17 Jan 2008
Accepted
02 May 2008
First published
09 Jun 2008

J. Environ. Monit., 2008,10, 837-841

Return period of enhanced gamma ray dose rates: regional differences observed in Japan

Y. Inomata, Y. Igarashi, M. Chiba, M. Aoyama and K. Hirose, J. Environ. Monit., 2008, 10, 837 DOI: 10.1039/B800893K

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