Selected papers: Preface. Modelling of radiocesium in lakes — on predictive power and lessons for the future (L. Håkanson). Present thoughts on the aquatic countermeasures applied to regions of the Dnieper river catchment contaminated by the 1986 Chernobyl accident (O. Voitsekhovitch et al.). The role of a spring river as a source of 137Cs in a lagoon environment: the case of the Stella river (Marano lagoon, Northern Adriatic Sea) (M. Belli et al.). Mobilization studies of 137Cs in sediments from Rochedo Reservoir, Goiânia, Go., Brazil (M.E.M. De Luca, J.M. Godoy). Migration and modelling of tritium in waste water reservoirs and a retention pond (M. Fukui). Long-term kinetics of radiocesium fixation by soils (A. Konoplev et al.). On the differential binding mechanisms of radiostrontium and radiocaesium in sediments (M.J. Madruga, A. Cremers). Recent radioecological investigations in the Austrian part of the Danube river (F.J. Maringer et al.). Contamination of fish with 137Cs in Kiev reservoir and old river bed of Pripyat near Chernobyl (R.H. Hadderingh et al.). Radioecology assessment in waterways in France with nuclear facilities (1989-1993) (L. Foulquier, A. Lambrechts). The modelling concept for the radioactive contamination of waterbodies in RODOS, the decision support system for nuclear emergencies in Europe (W. Raskob et al.).