[Comparative analysis of natural uranium mobility and concentration process in ecosystems of the Pechora river basin].

Natural uranium mobility and its concentration process in water ecosystems of the Pechora river basin situated in the areas with the uranium increased concentration in rocks and in the zone around radioactive waste repository were compared. The study investigated the influence of the environmental factors on the uranium distribution in water reservoirs. In the studied ecosystems, Fe-bearing compounds are major sorbents of uranium during the migration and concentration process. Nitrate-ions increase the uranium mobility in the ecosystems. The influence of sulfate, phosphate and carbonate complexation on the uranium distribution between water and bottom sediments wasn't pronounced in the ecosystems with high natural radioactivity, but significant for the radioactively contaminated water reservoirs. Uranium geochemical mobility is higher in contaminated water ecosystems. The uranium content in the water from this area substantially exceeds the background value for the region and toxicity limits for hydrophytes. Comparison of the current and earlier received data shows that the uranium concentration in the water has decreased, its specific activity in sediments has enhanced. The level of the uranium concentration in dry hygrophyte biomass has not changed.

Determination of 226Ra and 228Ra in slightly mineralised natural waters.

A radiochemical method for simultaneous separation of (226)Ra and (228)Ra from natural waters by precipitating the radionuclides in the form of chromates that have low solubility in weak acetic acid has been described. For analytical purposes the change into soluble state was achieved through high-temperature melting the radium chromates precipitate with sodium and potassium carbonates at certain ratios. The chemical yield for radium-226 amounted to 87.1 ± 1.4% at the efficiency of counting 92.8 ± 0.7%. Calculated in series of 20 parallel determinations, reproducibility of the method was 7%. The chemical yield in separating radium-228 made up 63.8 ± 1.1%.