Uranium isotopes in waters and bottom sediments of rivers and lakes in Poland

Activity concentrations of U-238, U-234 and U-235 were determined in waters and bottom sediments in two main rivers in Poland (the Vistula and Odra rivers) with their tributaries, in four coastal rivers and in six lakes. Concentrations of U-238 and U-234 were compared with the concentrations of Ra-226 determined in another study. As compared with concentrations in coastal rivers and in lakes, enhanced concentrations of the radionuclides were observed in water and bottom sediments in the upper and middle courses of the Vistula river, whereas in the Odra river the enhanced concentrations were present only in the bottom sediments. The enhanced concentrations in the Vistula river result from the discharge of coal mine waters from the Upper Silesian Coal Basin, and they indicate that the discharge was continued. The enhanced concentrations in the Odra river observed only in bottom sediments indicate that the discharge occurred in the past. The U-234/U-238 ratio for the bottom sediments was close to unity, indicating that these isotopes were close to equilibrium, whereas for water the average ratio was from 1.2 for takes to 1.5 for the Vistula river, demonstrating the lack of equilibrium.