Soluble and particle-bound Po-210 and Pb-210 in groundwaters

The presence in groundwater of Po-210 and Pb-210 in particles of different sizes was determined. Three different groundwaters were filtered with five membranes with pore sizes ranging from 0.8 mu m to 5 kD and the retention o f Po-201 by these membranes was determined. The same was done for Pb-210 wi th three membranes with pores between 0.45 mu m and 5 kD. Only in one of th ese waters was a considerable fraction, about 20%, of both radionuclides fo und to be present in the soluble form, i.e. passing though the membrane wit h the smallest pore size. In the other waters only 1-2% of Po-210 and Pb-21 0 was soluble. The sizes of particles carrying the radionuclides varied fro m water to water. In most waters the radionuclides were evenly distributed in particles of varying size. In one water, however, about 80% of Pb-210 wa s found in the course particle fraction with a diameter higher than 450 nm and in another water about 50% of Po-210 was in the intermediate size fract ion of 100-450 nm. It is expected that neither Pb nor, especially Po would form intrinsic precipitates but they would be adsorbed on colloidal mineral s and organics. It was also found that large fractions of both radionuclide s were adsorbed in the filtration system, filters and vessels.