Role of Suspended Matter and Dissolved Organic Substances in Behavior and Migration of Anthropogenic Radionuclides in River-Sea Aquatic Systems

Distribution of Cs, Sr, and Pu nuclides between suspended matter and the aqueous phase and the features of interaction of these radionuclides with dissolved organic matter are studied, to gain a better insight into the radionuclide behavior in the Ob and Yenisei estuaries and adjacent Kara Sea. For radionuclide speciation, the experimental study included determination of the radionuclide activities in aqueous solutions after filtration and ultrafiltration of large-volume water samples and membrane fractionation of small-volume water samples by passing the solution through a cartridge with filters of regularly decreasing pore size followed by mass-spectrometric determination of elements. In the water-soluble fraction, the ¹³⁷Cs activity increases with increasing salinity, whereas that of ⁹⁰Sr decreases, which can be attributed to the differences in the physicochemical behavior of the radionuclides in solutions and also to the effect of contamination sources. In seawater, suspended material can retain 1-10% of ¹³⁷Cs and ⁹⁰Sr. In the estuarine zones, these values can be 20-40%. More than 50% of ⁹⁰Sr and ^239,240Pu are associated with dissolved organic matter. In saline water this effect is less pronounced.