In a study investigating biogeochemical mechanisms for chromium reduction in Hanford 100H aquifer sediments, flow-through laboratory columns were subject to anaerobic, synthetic groundwater containing Cr(VI) and lactate in the presence of different electron acceptors [NO3-, Fe(III), and SO42-]. Cr(VI) was depleted in the effluent solutions of the nitrate-treated columns, all of which exhibited denitrifying conditions, as well as in some of the sulfate-amended columns where fermentative conditions were dominant. Micro X-ray fluorescence mapping showed the presence of freshly precipitated mixed phase Cr(III)-Fe(III) (hydr)oxides in all the column sediments. Analysis of XANES spectra indicate that the Cr(III) particles most closely resemble standards produced by abiotically reacting Cr(VI) with biogenically-reduced Fe(II), and are distinct from abiotically synthesized mixed phase Cr-Fe hydroxides. These results suggest that mixed CrxFe1-x(OH)3 materials made under realistic subsurface conditions or in biotic cultures are structurally different from those materials synthesized through common abiotic synthetic methods.

Spectroscopic studies of chromium bioremediation products in flow-through column sediments

243rd National Meeting (2012)

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