High nitrate concentration together with high salinity of the groundwater in the area of Lake Karachai may enhance the activity of halophilic and denitrifying microorganisms. Those microorganisms affect transformation of chemical species of radionuclides through the function of cellular compounds as carboxyl and phosphoryl functional groups. Coordination environments of biosorbed Eu(III) by Halomonas sp. and P. denitrificans measured by time-resolved laser-induced fluorescence spectroscopy (TRLFS) showed that Eu(III) was coordinated with the functional groups. Even though clay mineral kaolinite is well known to adsorb cationic metal ions, SEM-EDS and TEM-EDS analyses of the U- and Pu-accumulated mixture of B. subtilis cells and kaolinite from the solution containing UO22+ and PuO22+ revealed that most of U and Pu were associated with B. subtilis cells in the mixtures. These results show that microbial cells possess higher sorption ability of U(VI) and Pu(VI) than clay mineral of kaolinite. U(VI) and trivalent actinides (An(III)) formed U(VI)- and An(III)-phosphate minerals on the cell surface of microorganisms. This mineralization resulted from post-sorption process, where U(VI) and An(III) were instantaneously sorbed on the cell surfaces of microorganisms, followed by the reaction with essential element of P released from the yeast to form U(VI)- and An(III)-phosphate minerals. During the formation of biological carbonate mineralization, coprecipitation of radionuclides is another process for retarding migration of actinides and Sr. Unicellular fungus yeast Saccharomyces cerevisiae accumulated radioactive Cs inside cells. Therefore, microorganisms play an important role for the migration of radionuclides including actinides in groundwater around Lake Karachai.
All Science Journal Classification (ASJC) codes
- 化学 (全般)