Abstract
AbstractThe role of the microbial activity on the transport properties of host rocks for geological repositories, particularly in the far-field, is an area of active research. This paper compares results from experiments investigating changes in transport properties caused by microbial activity in sedimentary rocks in Japan (mudstones) and sandstone (UK).These experiments show that both Pseudomonas denitrificans and Pseudomonas aeruginosa appear to survive and thrive in pressurized flow-through column experiments which utilized host rock materials of relevance to radioactive waste disposal. Indeed, despite there being a difference in the numbers of organisms introduced into both biotic experiments, numbers appear to stabilize at ∼105 ml−1 at their completion. Post experimental imaging has highlighted the distinct differences in biofilm morphology, for the chosen rock types and bacteria, with Pseudomonas aeruginosa derived biofilms completely covering the surface of the sandstone host and Pseudomonas denitrificans forming biofilament structures. Regardless of substrate host or choice of microbe, microbial activity results in measurable changes in permeability. Such activity appears to influence changes in fluid flow and suggests that the transport of radionuclides through the far-field will be complicated by the presence of microbes.
Highlights
The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research
Denitrificans or P. aeruginosa) and (3) rock type, both column experiments showed that biofilm growth was possible
The comparative study has shown that both Pseudomonas denitrificans and through column experiments which utilised host rock materials of relevance to radioactive waste disposal: diatomaceous mudstone material
Summary
The significance of the potential impacts of microbial activity on the transport properties of host rocks for geological repositories is an area of active research. Most work has focussed on far-field environs, in granite (Sweden) and mudstone (Japan), where far-field is considered to be the geosphere beyond the repository. Because the UK does not yet have a potential site for deep geological disposal of radioactive waste, British research programmes involving biogeochemical processes (such as BIGRAD consortium (http://www.nerc.ac.uk) and the BGS BioTran project (http://www.bgs.ac.uk)) are focussing on “generic” rock types with a mineralogy that could be considered broadly similar to that of a potential host UK geology. This paper compares some of the results obtained from flow-through column experiments investigating transport processes in Japanese mudstones and Sherwood sandstone
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