ABSTRACTBiofilms were grown in situ 296 metres below sea level in the Äspö Hard Rock Laboratory. The prominent organism in these biofilms wasGallionella ferruginea, which is an iron oxidising chemolithotrophic microorganism that grows in low oxygen conditions. This organism grows an organic stalk structure capable of binding and concentrating trace metals. This stalk structure also allows amorphous ferric iron oxyhydroxides, or BIOS, (bacteriogenic iron oxides) to precipitate. The pH of the groundwater within the system was between 7.4 and 7.6, with Eh potential between 150 and 190 mV and oxygen saturation between 3 and 15%. Biofilms developed within two weeks and were sampled every two weeks for three months. Cell number and stalk length was recorded for each sample. The concentration of Cr, Ni, Cu, Zn, Mo, REE (rare earth elements), U-238 and Th-232 was measured by ICP-MS. Early results suggested thatGallionellabiofilms and associated BIOS could potentially concentrate trace metals up to 1000 fold higher than levels within the host rock and over 1 000 000 times the levels in the groundwater over a period of years. These new experiments indicate thatGallionellabiofilms and BIOS can rapidly attenuate metals to levels over 1000 fold higher than the levels in the groundwater. This process can occur anywhere where reduced groundwater enters the waste repository tunnel, open cavities or where groundwater extrudes at the surface. Because of this, there is huge potential to use biofilms and BIOS for retention of radionuclides and pollution control.
Correction to: Uranium and neptunium retention mechanisms in Gallionella ferruginea/ferrihydrite systems for remediation purposes