Electron Energy-Loss Safe-Dose Limits for Manganese Valence Measurements in Environmentally Relevant Manganese Oxides

• Published in: Environmental science & technology Vol. 46; no. 2; pp. 970 - 976
• Main Authors: Livi, Kenneth J. T, Lafferty, Brandon, Zhu, Mengqiang, Zhang, Shouliang, Gaillot, Anne-Claire, Sparks, Donald L
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 17.01.2012
• Subjects: Condensed Matter; Earth sciences; Earth, ocean, space; Electrons; Engineering and environment geology. Geothermics; Environmental Monitoring - methods; Exact sciences and technology; Manganese Compounds - chemistry; Marine and continental quaternary; Materials Science; Measurement; Oxidation; Oxidation-Reduction; Oxides - chemistry; Physics; Pollution, environment geology; Spectroscopy, Electron Energy-Loss - methods; Surficial geology; Time series; Transmission electron microscopy; experimental studies; chromium; environment protection; oxides; oxidation; arsenic; pollution; manganese; laboratory studies
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es203516h

Manganese (Mn) oxides are among the strongest mineral oxidants in the environment and impose significant influence on mobility and bioavailability of redox-active substances, such as arsenic, chromium, and pharmaceutical products, through oxidation processes. Oxidizing potentials of Mn oxides are determined by Mn valence states (2+, 3+, 4+). In this study, the effects of beam damage during electron energy-loss spectroscopy (EELS) in the transmission electron microscope have been investigated to determine the “safe dose” of electrons. Time series analyses determined the safe dose fluence (electrons/nm2) for todorokite (106 e/nm2), acid birnessite (105), triclinic birnessite (104), randomly stacked birnessite (103), and δ-MnO2 (<103) at 200 kV. The results show that meaningful estimates of the mean Mn valence can be acquired by EELS if proper care is taken.