• Journal Article

Real-time characterization of biogeochemical reduction of Cr(VI) on basalt surfaces by SR-FTIR imaging

Citation

Holman, H-Y. N., Perry, D. L., Martin, M. C., Lamble, G. M., McKinney, W. R., & Hunter-Cevera, J. (1999). Real-time characterization of biogeochemical reduction of Cr(VI) on basalt surfaces by SR-FTIR imaging. Geomicrobiology Journal, 16(4), 307-324. DOI: 10.1080/014904599270569

Abstract

Abstract
Synchrotron radiation-based (SR) Fourier-transform infrared (FTIR) spectromicroscopy in the mid-infrared region is a surface analytical technique that can provide direct insights into the localization and real-time mechanisms for the reduction of the (CrO4)2- chromate [Cr(VI)] species on surfaces of geologic materials. Time-resolved SR-FTIR spectra indicate that, in the presence of endoliths (mineral-inhabiting microorganisms), microbial reduction of Cr(VI) to Cr(III) compounds on basaltic mineral surfaces is the key mechanism of Cr(VI) transformation. It proceeds in at least a two-step reaction with Cr(V) compounds as possible intermediate products, with the reduction of Cr(VI) increasing during the concomitant biodegradation of a dilute organic vapor (toluene). Analyses of spatially resolved SR-FTIR spectra show that the maximum reduction of Cr(VI) to Cr(III) compounds occurs on surfaces densely populated by microorganisms. The oxidation state of Cr(III) compounds was confirmed by micro-x-ray absorption fine-structure spectroscopy. Both the time- and space-resolved SR-FTIR spectra show that in the absence of endoliths, Cr(VI) reduction is insignificant. With this effort, the potential use of SR-FTIR spectromicroscopy in providing mechanistic information of reduction of Cr(VI) has been demonstrated. This method can now be expanded to examine other IR-amenable microbial/chemical contaminant systems