Influence of plowing on the depth distribution of various radionuclides in the soil

The present work deals with a comparison of the vertical distribution of ¹³⁷Cs, ¹³⁴Cs, ¹⁰⁶Ru, ¹²⁵Sb, and ⁹⁰Sr at two agricultural sites in Styria (Austria) in the first two years after the Chernobyl fallout. Three months after deposition the Chernobyl derived radionuclides had their maximum concentrations in the first cm. Detectable amounts, however, had penetrated down to a depth of 12 cm (Stagno-Dystric Gleysol, site A) and 20 cm (Dystric Cambisol, site B). Significant differences between the two sites were observed after the first plowing. At site A a new concentration maximum at 15 to 18 cm depth was observed due to an extreme turnover effect. Even the second plowing in 1988 did not yield a homogeneous radionuclide distribution over the tillage depth. At site B the furrow slice was twisted only 60° against the slope gradient. This resulted in a slight mixing in the first 12 cm. From this it may be concluded that plowing does not lead to a thorough mixing in any case. At least two or three plowing steps may be needed to obtain an uniform nuclide distribution at certain sites.