The Distribution of Fallout Cesium‐137 in Southern Saskatchewan, Canada

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Abstract
Cesium‐137 is a radioactive fallout isotope that is strongly adsorbed by soil particles and has been used by numerous researchers to estimate soil erosion and deposition. In this study, background or baseline levels of 137Cs on native, noneroded soils in southern Saskatchewan are presented. The activity of 137Cs in well‐drained, native soils was measured at 363 sites in the agricultural portion of Saskatchewan. The 137Cs activity at these sites was believed to reflect fallout input to the land surface and therefore represent the background 137Cs activity levels for the sites. In this regional study, 137Cs activity levels in native soils were found to range from 840 to 4570 Bq m−2, with a mean of 2422 ± 505 Bq m−2. The spatial variation in 137Cs activity was complex, and could not be adequately described by a second‐order trend surface function. In the study area there was a general trend toward increasing 137Cs activity with increasing precipitation during the peak fallout period; however, the relationship showed a great deal of scatter. The variation in 137Cs activity levels in the native soils was considered to be largely caused by local meteorological conditions during the peak 137Cs fallout period. Accurate local determination of background 137Cs activity levels for erosional studies in southern Saskatchewan must be based on local sampling of native soils, as predictions based on either location or local precipitation amounts are unlikely to be adequate.