Francis and Nancharaiah reported in 2015 in Chapter 9 of the text: Environmental Remediation and Restoration of Contaminated Nuclear and Norm Sites. that radioactive contamination of the environment is a global problem arising from generating nuclear power [Very little], nuclear accidents [Very little, except Chernobyl], from testing nuclear weapons [Yes], and from disposing of nuclear waste [Only a few issues].
Microorganisms potentially can solubilize and immobilize a wide range of naturally occurring radionuclides, actinides, and fission products. Their ability to do so encompasses several mechanisms, such as oxidation–reduction reactions, the production of sequestering agents, bioaccumulation, and biocrystallization. Currently, such microbial processes are exploited to remediate radionuclide-contaminated environments.
In this chapter we briefly review the key microbial processes and the mechanisms underlying the biotransformation of radionuclides of concern, and consider their potential application for in situ or ex situ bioremediation of radionuclide-contaminated soils, sediments, and wastes.
The authors concluded that microorganisms play a major role in the environmental mobilization and immobilization of radionuclides. Such microbial processes are being exploited to extract or stabilize radionuclide-contaminated soils. However, the biochemical mechanisms of biotransformation of the various chemical forms of radionuclides found in contaminated soils are not fully understood, and consequently, in situ or ex situ bioremediation of contaminated soils has not been deployed. Based on our current understanding of uranium biogeochemistry, it appears that microbial reductive precipitation of uranium is an attractive in situ bioremediation process that can be developed further provided that reducing conditions can be maintained to limit the re-oxidation and remobilization of sequestered uranium.
Alternatively, extracting uranium from contaminated soils by carbonate or citric acid is a potentially promising ex situ process that was validated in laboratory and batch studies. The microbially induced calcite precipitation of strontium via bacterial ureolysis as an in situ process was demonstrated in laboratory- and simulated field-scale studies. The short half-life of 90Sr (29 years) and the long-term stability of calcite make this coprecipitation process
very attractive for sequestering the radionuclide that it would permit sufficient time for radioactivity to decay.
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