Ecological risks in some sites in Kaluga region contaminated with radionuclides as a result of the Chernobyl accident

The study was aimed to evaluate ecological risks in some sites in Kaluga region contaminated with radionuclides following the Chernobyl accident. Data of the "Chernobyl" data base were used for risk evaluation. Dose rates to biota and ecological risks were evaluated in accordance with recommendations of "Roshydromet" and ICRP (Publication 108). Density of soil contamination with radionuclides in May 1986 was evaluated with the use of measured data and calculated isotope ratios. The highest calculated dose rate to reference organisms was 0.19-0.46 mGy/d in the first period after the accident, it was below the level of ecological safety. The main contributor to radiation dose to plants and soil invertebrates was soil radionuclides. The main contributors to dose to vertebrates were external radiation and internal exposure to incorporated radionuclides. In the first period following the accident some vertebrates and the pine tree received the highest radiation doses. Radionuclides 131I, 140Ba+140La were the main contributors to dose to the reference organisms. Cesium radionuclides were main contributors to dose to vertebrates; radionuclides 140Ba+140La were main contributors to dose to plants and soil invertebrates. In May 1986 contribution of short-living radionuclides to dose was 30-80%. In the course of time contribution of 137Cs to dose increased. At present time in all sites contaminated in 1986 the level of radiation is lower, than the level, which ensures preservation of favorable environment. Results presented in the article can be useful for study of dynamics of ecological risk values and for planning radioecological monitoring the sites affected by radiation as a result of radiological events.