External γ-dose rates delivered from the Chernobyl fallout in Belarus

The γ-dose rates in air were measured in time at various reference sites which had different environmental characteristics. It appears that the dose rate had fallen off from its peak value and more or less stabilized by the end of 1990. The model presented describes this behaviour and fits the experimental data well. All the study sites are subdivided into four groups according to the dose-decrease time constants which range between 2.9 and 7.1 years. Causes of such different temporal decreases at various sites are discussed. Dose commitment conversion factors were computed which allow estimation of external dose commitments at every site for various time periods. The findings may be applicable to other sites in Belarus with similar climate and landscape characteristics.