Latitudinal distribution of cesium-137 fallout in 1990 on Saxifraga oppositofolia from Ellesmere Island, Canada

Abstract

During the first ski traverse of Ellesmere Island in spring 1990, purple saxifrage (Saxifraga oppositifolia) was collected at 10 sites from 76 to 82°N. Measured 137Cs levels in this cushion plant displayed a progressive decrease in activity north of 78°, reflecting past global patterns of radionuclide fallout. Lower 137Cs activity at the southern end of Ellesmere Island may reflect a northward shift of the distribution maximum since a previous latitudinal survey conducted in 1979–1980. Levels of 137Cs in three species of lichens were consistently higher than those for nearby saxifrage, possibly owing to the larger exposure to fallout for much of the year and the slower rate of lichen growth. In support of previous research, no 134Cs was detected, which indicated that Chernobyl fallout had not been deposited in significant quantities at these extreme northern latitudes. Specific activities in 1990 of saxifrage samples were compared with similar samples collected during 1979–1980 to derive an effective half-life of 6.2 ± 1.0 years for northern Ellesmere Island. Key words: cesium, fallout, Ellesmere Island, saxifrage, half-life.