Speciation and Quantitative Mapping of Metal Species in Microbial Biofilms Using Scanning Transmission X-ray Microscopy

Authors

James J. Dynes, McMaster University
Tolek Tyliszczak, Lawrence Berkeley National Laboratory
Tohru Araki, McMaster University
John R. Lawrence, National Water Research Institute, Saskatoon, Saskatchewan
George D. W. Swerhone, National Water Research Institute, Saskatoon, Saskatchewan
Gary G. Leppard, National Water Research Institute, Burlington, Ontario
Adam P. Hitchcock, McMaster University

Date of this Version

2006

Comments

Published in Environmental Science & Technology Vol. 40, No. 5, 2006.

Abstract

A scanning transmission X-ray microscope illuminated with synchrotron light was used to investigate the speciation and spatial distributions of metals in a microbial biofilm cultivated from river water. Metal 2p absorption edge signals were used to provide metal speciation (through shapes of the absorption spectra) and quantitative spatial distributions of the metal species. This paper presents sample data and describes methods for extracting quantitative maps of metal species from image sequences recorded in the region of the metal 2p edges. Comparisons were made with biochemical characterization of the same region using images recorded at the C 1s and O 1s edges. The method is applied to detailed quantitative analysis of ferrous and ferric iron in a river biofilm, in concert with mapping Ni- (II) and Mn(II) species in the same region. The distributions of the metal species are discussed in the context of the biofilm structure. These results demonstrate that soft X-ray STXM measurements at the metal 2p absorption edges can be used to speciate metals and to provide quantitative spatial distribution maps for metal species in environmental samples with 50 nm spatial resolution.