Speciation-dependent toxicity of Neptunium(V) toward Chelatobacter heintzii

James E. Banaszak, Donald T. Reed, Bruce E. Rittmann

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19 Scopus citations


This work investigates how chemical speciation controls the toxicity of neptunium and the neptunium - NTA complex toward Chelatobacter heintzii. We studied the effect of aquo and complexed/precipitated neptunium on the growth of C. heintzii in noncomplexing, glucose and phosphate-buffered nitrilotriacetic acid (NTA) growth media. Equilibrium chemical speciation modeling and absorption spectroscopy were used to link neptunium speciation to biological growth inhibition. Our results show that metal toxicity of aquo NpO2+ significantly limits the growth of C. heintzii at free metal ion concentrations greater than ≃10-5 M. However, neptunium concentrations ≤10-4 M do not cause measurable radiotoxicity effects in C. heintzii when present in the, form of a neptunium - NTA complex or colloidal/precipitated neptunium phosphate. The neptunium - NTA complex, which is stable under aerobic conditions, is destabilized by microbial degradation of NTA. When phosphate was present, degradation of NTA led to the precipitation of a neptunium-phosphate phase.

Original languageEnglish (US)
Pages (from-to)1085-1091
Number of pages7
JournalEnvironmental Science and Technology
Issue number8
StatePublished - Apr 15 1998
Externally publishedYes

ASJC Scopus subject areas

  • General Chemistry
  • Environmental Chemistry


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