Original Paper


, Volume 22, Issue 5, pp 921-929

First online:

Bacterial Pu(V) reduction in the absence and presence of Fe(III)–NTA: modeling and experimental approach

  • Randhir P. DeoAffiliated withChemistry Department, Division of Natural Sciences, College of Natural and Applied Sciences, University of Guam Email author 
  • , Bruce E. RittmannAffiliated withCenter for Environmental Biotechnology, Biodesign Institute, Arizona State University
  • , Donald T. ReedAffiliated withLos Alamos National Laboratory, Environmental and Earth Sciences Division, Carlsbad Environmental Monitoring and Research Center

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Plutonium (Pu), a key contaminant at sites associated with the manufacture of nuclear weapons and with nuclear-energy wastes, can be precipitated to “immobilized” plutonium phases in systems that promote bioreduction. Ferric iron (Fe3+) is often present in contaminated sites, and its bioreduction to ferrous iron (Fe2+) may be involved in the reduction of Pu to forms that precipitate. Alternately, Pu can be reduced directly by the bacteria. Besides Fe, contaminated sites often contain strong complexing ligands, such as nitrilotriacetic acid (NTA). We used biogeochemical modeling to interpret the experimental fate of Pu in the absence and presence of ferric iron (Fe3+) and NTA under anaerobic conditions. In all cases, Shewanella alga BrY (S. alga) reduced Pu(V)(PuO2 +) to Pu(III), and experimental evidence indicates that Pu(III) precipitated as PuPO4(am). In the absence of Fe3+ and NTA, reduction of PuO2 + was directly biotic, but modeling simulations support that PuO2 + reduction in the presence of Fe3+ and NTA was due to an abiotic stepwise reduction of PuO2 + to Pu4+, followed by reduction of Pu4+ to Pu3+, both through biogenically produced Fe2+. This means that PuO2 + reduction was slowed by first having Fe3+ reduced to Fe2+. Modeling results also show that the degree of PuPO4(am) precipitation depends on the NTA concentration. While precipitation out-competes complexation when NTA is present at the same or lower concentration than Pu, excess NTA can prevent precipitation of PuPO4(am).


Plutonium Shewanella alga Bacterial reduction NTA Iron Bioreduction Modeling