RELATIONSHIP BETWEEN CS-137 IN SOME UNDISTURBED NEW-ZEALAND SOILS ANDRAINFALL

Soil samples were collected from 10 undisturbed sites in South Canterb ury and Manawatu, New Zealand, to examine the relationship between Cs- 137 in soils and rainfall. The results were used to test a previously derived model relating cumulative deposition of Cs-137 from atmospheri c fallout to mean annual rainfall. There were strong correlations betw een mean measured levels of Cs-137 in soils from the undisturbed sites and rainfall, and between the mean measured levels in soils and those predicted by the model. The moder can therefore be used to estimate i nput levels of Cs-137 for erosion studies and to verify the suitabilit y of local measurements of the input value from sites assumed to be un disturbed. Coefficients of variation in soil-Cs at the undisturbed sit es ranged up to 30%, indicating that up to 10 samples may be needed to estimate the input value with a standard error +/-10%.