Microbial Mineral Transformations at the Fe(II)/Fe(III) Redox Boundary for Solid Phase Capture of Strontium and Other Metal/Radionuclide Contaminants

摘要

The migration of (sup 90)Sr in groundwater is a significant environmental concern at former nuclear weapons production sites in the US and abroad. Although retardation of (sup 90)Sr transport relative to mean groundwater velocity is known to occur in contaminated aquifers, Sr(sup 2+) does not sorb as strongly to iron oxides and other mineral phases as do other metal-radionuclides contaminants. Thus, some potential exists for extensive (sup 90)Sr migration from sources of contamination. Chemical or biological processes capable of retarding or immobilizing Sr(sup 2+) in groundwater environments are of interest from the standpoint of understanding controls on subsurface Sr(sup 2+) migration. In addition, it may be possible to exploit such processes for remediation of subsurface Sr contamination. In this study the authors examined the potential for the solid phase sorption and incorporation of Sr(sup 2+) into carbonate minerals formed during microbial Fe(III) oxide reduction as a first step toward evaluating whether this process could be used to promote retardation of (sup 90)Sr migrations in anaerobic subsurface environments. The demonstration of Sr(sup 2+) capture in carbonate mineral phases formed during bacterial HFO reduction and urea hydrolysis suggests that microbial carbonate mineral formation could contribute to Sr(sup 2+) retardation in groundwater environments. This process may also provide a mechanism for subsurface remediation of Sr(sup 2+) and other divalent metal contaminants that form insoluble carbonate precipitates.