The turnover of cesium-137 within a forest ecosystem described by a compartment modelling approach — Gideå study site, Sweden

A new comprehensive data base including catchment area characteristics and information about radionuclides deposition, migration in soil and transport in groundwater within the catchment ‘Orrmyrbäcken’ has been studied when modelling the turnover of cesium-137 within the Gideå study site. The BIOPATH code (compartment technique) was used to describe the long-term transfer within the whole catchment area. The concentrations of cesium-137 in surface water and soil were used for evaluation of the model. The model describes the concentration in surface water quite well. The initial transfer to the water, during the time when the snow melted cannot be evaluated due to lack of observed data. One of the results, was that about 5% of the initially deposited cesium-137 had left the catchment area after 5 years. Uncertainty analysis has been performed to identify the importance of different parameters. The source term, i.e. the deposition, initially contributes most to the uncertainty of the concentration in surface water and groundwater as well as in soil and peat. Furthermore, the water turnover and Kd-values in soil will increase their importance with increasing time.