B43F-2583 Vertical distribution of Chernobyl-derived 137 Cs in bottom sediments represents long-term dynamics of water contamination Konoplev A. 1 , Laptev G. 2 , Golosov V. 3 , Ivanov M. 3 , Igarashi Y. 1 , Nanba K. 1 1 Institute of Environmental Radioactivity Fukushima University, Fukushima, Japan; 2 Ukrainian Hydrometeorological Institute, Kiev, Ukraine; 3 M.V. Lomonosov Moscow State University, Moscow, Russia Long-term dynamics of radionuclides in the environment has become particularly relevant today, 33 years after the Chernobyl accident. Bottom sediments of lakes and reservoirs provide insight in understanding time changes of radionuclides strongly bound to sediment particles such as 137 Cs. A number of cores of bottom sediments were collected in 2018 in deep parts of Lake Glubokoe, Lake Azbuchin and Cooling Pond (CP) in close vicinity of the Chernobyl NPP and in Schekino reservoir (Upa River) in Tula region of Russia. Results The obtained 137 Cs vertical distributions in sediments suggest that no vertical mixing of sediments has occurred, and the 137 Cs peaks are well-defined and not diffuse ones. Assuming that sedimentation rates after the accident were more or less uniform, layers of bottom sediments can be attributed to certain time. We obtained the dynamics of particulate 137 Cs activity concentrations from 1986 to 2018. Using experimental values of the distribution coefficient K d , changes in the dissolved 137 Cs activity concentrations in the above water bodies have been estimated for the period of 32 years after the accident. The estimates of dissolved 137 Cs concentrations are in reasonable agreement with monitoring data. The general trend of the particulate and dissolved 137 Cs and 241 Am activity concentrations in all water bodies apparently can be described by the semi-empirical “diffusional” model. 137 Cs deposition in Belarus, Russia and Ukraine Water bodies under study in Chernobyl Exclusion Zone (Ukraine) Upa River Catchment in Tula region (Russia) Bottom sediments core sampling at Glubokoe, Azbuchi lakes, Cooling Pond and Schekino Dam reservoir Vertical distributions of radionuclides in Glubokoe, Azbuchi lakes and Schekino Dam reservoir Semiempirical “diffusional” model of radionuclide long-term dynamics in lakes and rivers Acknowledgement This research was supported partly by bilateral project of Russian Foundation for Basic Research (RFBR) and Japan Society for Promotion of Science (JSPS) and by Science and Technology Research Partnership for Sustainable Development (SATREPS), Japan Science and Technology Agency (JST)/Japan International Cooperation Agency (JICA) (JPMJSA1603). Reconstructed dissolved 137 Cs in Upa River against monitoring data Reconstructed dynamics of dissolved 137 Cs in lake Glubokoe against data of monitoring and diffusional model ESSOAr | https://doi.org/10.1002/essoar.10501729.1 | CC_BY_4.0 | First posted online: Wed, 22 Jan 2020 17:58:18 | This content has not been peer reviewed.