Chapter 3.3 Forward and inverse modelling of radioactive pollutants dispersion after Chernobyl accident

The paper re-analyses the consequences of Chernobyl catastrophe for the radionuclide contamination of the European region. In the re-analysis, we tried to use the best available information and establish the ground for the source-apportionment studies, similar to those conducted by the team for ETEX experiment. The modelling tool used in the simulations was the Finnish Emergency and Air Quality modelling system SILAM v.3.8, which is based on a Lagrangian Monte-Carlo random-walk. The system was run through the 1-month-long period with the source-term information for 22 nuclides, which altogether comprise >99% of the total inventory of the release, and varying vertical emission profile, which reflected the different stages of the accident. This information and detailed meteorological data from the state-of-the-art NWP model HIRLAM, which was re-run for the considered period, resulted in accurate reproduction of the contamination pattern and its motions over Europe. Comparison of the simulated deposition map with the results of the radioactive deposition atlas of Europe showed very good agreement between the patterns. However, source-apportionment simulations showed insufficient both temporal resolution and spatial coverage of the data, and thus are not discussed in details.