Speciation-Dependent Toxicity of Neptunium(V) Toward Chelatobacter heintzii

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 nitrilotriace...

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Bibliographic Details
Published in:Environmental science & technology 1998-04, Vol.32 (8), p.1085-1091
Main Authors: Banaszak, James E, Reed, Donald T, Rittmann, Bruce E
Format: Article
Language:English
Subjects:
Action of physical and chemical agents on bacteria
BACTERIA
Bacteriology
Biological and medical sciences
Chelatobactor heintzii
CHEMICAL STATE
Chemicals
Fundamental and applied biological sciences. Psychology
GROWTH
INHIBITION
Metals
Microbiology
NEPTUNIUM
NEPTUNIUM COMPLEXES
Pollution control
RADIATION, THERMAL, AND OTHER ENVIRONMENTAL POLLUTANT EFFECTS ON LIVING ORGANISMS AND BIOLOGICAL MATERIALS
Radioactive elements
TOXICITY
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Summary: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 condi tions, is destabilized by microbial degradation of NTA. When phosphate was present, degradation of NTA led to the precipitation of a neptunium-phosphate phase.
ISSN:0013-936X
1520-5851
DOI:10.1021/es970664h