A long-term field study on the effect of acid irrigation and compensatory liming on the transport of Chernobyl-derived radiocesium in a forest soil

The effect of acid irrigation with and without liming on the vertical transport of Chernobyl-derived 134Cs in the soil was investigated in a Norway spruce stand by field experiments. For this purpose seven plots with different treatments were established. After 5 years of observation to detect differences in the residence half-timeʹs of 134Cs in the various soil horizons with respect to the control sites, the plots were sampled at 18 individual pits. No effect on the residence half-time of 134Cs was observed for ‘normal’ irrigation (pH 5.3) as compared to the control in all organic horizons. Following acid irrigation (pH 2.7), the transport of 134Cs was slightly enhanced as compared to ‘normal’ irrigation. The most significant effect was found for the limed plots: the transport of 134Cs was strongly retarded in the organic layer, as well in irrigated as in non-irrigated plots. These effects are discussed with respect to the different physico-chemical and biological conditions in the various plots and the consequences for the external gamma dose rate in air due to radiocesium in the soil.