Quantitative Determination of Fe-oxidation State by Electron Energy Loss Spectroscopy (EELS)

Abstract

The consequences of microbe-mineral interaction often resulted in the chemical, structural modification, or both in the biologically induced mineral. It is inevitable to utilize the high powered resolution of electron microscopy to investigate the mechanism of biogenic mineral transformation at nano-scale. The applications of transmission electron microscopy (TEM) capable of electron energy loss spectroscopy (EELS) to the study of microbe-mineral interaction were demonstrated for two examples: 1) biogenic illite formation associated with structural Fe(III) reduction in nontronite by Fe-reducing bacteria; 2) siderite phase formation induced by microbial Fe(III) reduction in magnetite. In particular, quan-tification of the changes in Fe-oxidation state at nanoscale is essential to understand the dynamic modification of minerals resulted from microbial Fe reduction. The procedure of EELS acquisition and advantages of EELS techniques were discussed .