Search for latitudinal trends in the effective half-life of fallout 137Cs in vegetation of the Canadian Arctic

Abstract

Using published data on the integrated deposition of fallout 90Sr (137Cs) until 1975 and current measurements of the,137Cs activity in plant communities along the latitudinal gradient north of 50° N, an estimate has been made of the 137Cs effective half-life, Teff, in the composite vegetation of the Canadian Arctic. The lichens Alectoria nigricans, Alectoria ochroleuca, Cladonia rangiferina, Cornicularia divergens, and Umbilicaria muhlenbergii were studied, as well as a moss, Polytrichum juniperinum, and the vascular cushion plants Dryas integrifolia, Saxifraga oppositifolia, and Silene acaulis. In all cases, the effective half-life increased with increasing latitude, the longest Teff (10–12 years) being exhibited by dry-habitat lichens at 80° N.