RELATIONSHIP BETWEEN CS-137 IN SOME UNDISTURBED NEW-ZEALAND SOILS AND RAINFALL

Soil samples were collected from 10 undisturbed sites in South Canterbury 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 atmospheric fallout to mean annual rainfall. There were strong correlations between 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 input levels of Cs-137 for erosion studies and to verify the suitability of local measurements of the input value from sites assumed to be undisturbed. Coefficients of variation in soil-Cs at the undisturbed sites ranged up to 30%, indicating that up to 10 samples may be needed to estimate the input value with a standard error +/-10%.