¹³⁷Cs migration and pro le in bottom sediments of deep drainage lakes, north-western Russia

Modern contamination of global and «Chernobyl» ¹³⁷Cs in lake-river systems bottom sediments is estimated. Drainage lakes of North-Western Russia were investigated. Kopanskoe Lake, located south of the Gulf of Finland, is on the trail of the «Chernobyl» ¹³⁷Cs fallout, whereas Ladoga, Sukhodolskoe, Vuoksa, Imandra lakes are located at its periphery, in Karelia and Kola Peninsula. Following parameters are distinguished: lakes bottom ¹³⁷Cs pollution density (kBq/m²), distribution of ¹³⁷Cs in the pro le of bottom sediments, ¹³⁷Cs di usion coe cients ( D ) in bottom sediments and content of the exchange chemical form of the radionuclide. ¹³⁷Cs contamination of the lakes was formed due to suspended matter sedimentation with ¹³⁷Cs, ¹³⁷Cs sorption and di usion in bottom sediments. With sedimentation ≥3 mm/year, the concentration of ¹³⁷Cs increased from the top to the bottom of the core (lakes Vuoksa, Ekostrovskaya Imandra), re ecting the gradual process of ¹³⁷Cs migration into the sediments. The opposite trend of ¹³⁷Cs concentration was observed in the bottom sediments of lakes Ladoga and Sukhodolskoe with sedimentation ≤0.5 mm/year. Here ¹³⁷Cs di usion with D = (0.5-6.2) ×10^-8 cm²/s caused slow radionuclide transfer in the bottom sediments. The main supply of ¹³⁷Cs was contained in the top layer 0-5 cm. 14.4-20 % of absorbed ¹³⁷Cs in lake Sukhodolskoye bottom sediments were was in an exchange chemical form, extracted into solution 1 М NH 4 Aс.

137Cs, 137Cs, lakes, bottom sediments, ¹³⁷Cs supply, sorption, di usion