Radiocesium contamination in a submediterranean semi-natural ecosystem following the Chernobyl accident: Measurements and models

Radiocesium dynamics in a Quercus conferta Kit ecosystem in Northern Greece have been extensively studied over the years 1993-1995. Radiocesium distribution in the different parts of the ecosystem was measured. A total 137Cs inventory of 243±66 MBq ha-1 due to the Chernobyl accident was measured in all parts of the ecosystem. Almost 90% of this inventory is still in the upper layers of the soil and the forest floor. In particular 13.4% is in the forest floor, 52.6% in the Ah horizon, and 23.4% in the upper 5 cm of the soil. Only 2.2% of this inventory is in the above ground biomass. The mean total 137Cs deposited on the forest floor from the above ground biomass is 0.18 MBq ha-1 y-1. Cesium leaching from the forest floor is negligible. The radiocesium distribution in soil is fixed and in equilibrium, at least since 1993. Most of radiocesium is not available for migration. Cesium migration in soil was modeled by (a) an open-quotes equivalent diffusionclose quotes model with different initial conditions and (b) a open-quotes compartmentclose quotes model derived from a diffusion-advection model. A compartment model for the contamination of living biomass is proposed. The total absorbed dose rate in air as well as the contribution due to 137Cs from the Chernobyl accident was determined inside the forest, by in-situ gamma spectrometry. 32 refs., 10 figs., 7 tabs