The Quantitative Accumulation of 95Zr + 95Nb and 140Ba + 140La in Carpets of Forest Moss. A Field Study

Abstract

During the 20 months from the beginning of the nuclear weapons tests in September 1961, the accumulation of fission products in carpets of forest moss vegetation was investigated. A number of moss samples as well as the precipitation were collected during the actual time period. With gamma spectrometric methods elaborate determinations of 95Zr + 95Nb and 140Ba + 140La these samples were made. The results show that the moss content of the fission products studied is greater than the corresponding integrated activity of the precipitation. A wash-out experiment indicated that no signigicant loss of these nuclides occurred from the moss. Therefore, from the results of the field study we conclude, firstly, that the actual nuclides are very efficiently absorbed in this plant and secondly that during a certain period of time there is a substantial dry deposition. From January 1962 to May 1963 the activity of 95Zr + 95Nb in moss vegetation has always been greater than 100 nCi/m2. The gamma exposure from 95Zr + 95Nb is discussed.