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 90 Sr ( 137 Cs) until 1975 and current measurements of the, 137 Cs activity in plant communities along the latitudinal gradient north of 50° N, an estimate has been made of the 137 Cs effective half-life, T eff , 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 T eff (10–12 years) being exhibited by dry-habitat lichens at 80° N.