105 V-4. APPLICATION TO THE BALTIC SEA In this particular application to the Baltic Sea, a constant and uniform suspended matter concentration over the domain, 4.5 mg/l, has been considered. The model was calibrated using the 137Cs inventories over the whole Baltic Sea in water and sediments estimated from measurements. A standard value, determined for Cs from experiments [V-11] was used for k2 and the forward rate, k1, can be determined from k2 and the equilibrium distribution coe?cient, kd, as explained in Refs. [V-6–9]: ?? = ? ?? ? ?? (V-20) Good results are obtained with kd = 3 m3/kg, which is close to the recommended value by the International Atomic Energy Agency [V-12]: 4 m3/kg. In addition, the sediment mixing depth (distance until which the dissolved phase interacts with the sediment) was set to 2 cm. Finally, a correction factor which takes into account that part of the sediment particle surface may be hidden by other sediment particles is introduced (? = 0.001). A detailed formulation of the model may be seen [V-6–9]. In summary, three parameters are optimized, i.e. the equilibrium distribution coe?cient, sediment mixing depth and sediment correction factor. Once the temporal evolution of 137Cs inventories in the Baltic Sea in the water column and sediments are adequately reproduced by the model, mean 137Cs concentrations in several sub-basins were extracted from the model, without any extra tuning, and compared with field data.