The potential of subterranean microbes in facilitating actinide migration at the Grimsel Test Site and Waste Isolation Pilot Plant

摘要

Microorganisms may affect the long-term stability and mobility of radionuclides disposed of in deep geological formations. Of particular concern is the association of radionuclides with subterranean microbial cells and their subsequent transport as biocolloids. We characterized the total microbial populations in two groundwater samples: one from the Culebra dolomite member of the Rustler Formation at the Waste Isolation Pilot Plant (WIPP), NM, and the other from the granitic formation at the Grimsel Test Site (GTS), Switzerland. Culebra groundwater (ionic strength 2.8 M, pH 7) contained 1.51+/-1.08 x 10(5) cells ml(-1), with a mean cell length of 0.75+/-0.04 mum and width of 0.58+/-0.02 mum. In contrast, low ionic-strength GTS groundwater (0.001 M, pH 10) contained 3.97+/-0.37 x 10(3) cells ml(-1), with a mean cell length of 1.50+/-0.141 mum and width of 0.37+/-0.01 mum. Adding appropriate electron donors and accepters to the groundwaters facilitated the growth of aerobic, denitrifying, fermentative, and acetogenic microorganisms. Uranium biosorption was studied in two isolates from these groundwaters, as well as several pure cultures from saline and non-saline environments. Halophilic and non-halophilic bacteria exhibited differences in the amount of U associated with the cells. Plutonium uptake by Acetobacteriurn sp, isolated from GTS varied from 30-145 pg of mu mg(-1) dry weight of cells. [References: 28]