Application of Synchrotron X-Ray Microbeam Spectroscopy to the Determination of Metal Distribution and Speciation in Biological Tissues
T. Punshon
Consortium for Risk Evaluation with Stakeholder Participation, Environmental
and Occupation Health Sciences Institute, Division of Life Sciences, Rutgers
University, Piscataway, New Jersy, USA
B. P. Jackson
Savannah River Ecology Laboratory, University of Georgia, Aiken, South
Carolina, USA
A. Lanzirotti
Consortium for Advanced Radiation Sources, The University of Chicago,
Chicago, Dlinois, USA
W. A. Hopkins and P. M. Bemch
Savannah River Ecology Laboratory, University of Georgia, Aiken, South
Carolina, USA
J. Burger
Consortium for Risk Evaluation with Stakeholder Participation, Environmental
and Occupation Health Sciences Institute, Division of Life Sciences, Rutgers
University, Piscataway, New Jersy, USA
Received 12 June 2004, Accepted 22 October 2004
This
paper was by special invitation as a contribution to a special issue of
the journal entitled" Application of Spectroscopic Methods to Environmental
Problems." The special issue was organized by Professor Peter A.
Tanner, Professor in the Department of Biology and Chemistry at City University
of Hong Kong.
Address correspondence to T. Punshon, Consortium for Risk Evaluation with
Stakeholder Participation, Environmental and Occupation Health Sciences
Institute, Division of Life Sciences, Rutgers University, 604 Allison
Road, Piscataway, NJ 08854, USA. E-mail: punshon@srel.edu
Abstract: Resolving the distribution and speciation of
metal(loid)s within biological environmental samples is essential for
understanding bioavailability, trophic transfer, and environmental risk.
We used synchrotron x-ray microspectroscopy to analyze a range of samples
that had been exposed to metal(loid) contamination. Microprobe x-ray fluorescence
elemental mapping (µSXRF) of decomposing rhizosphere microcosms
consisting of Ni- and U-contaminated soil planted with wheat (Triticum
aestivum) showed the change in Ni and U distribution over a 27-day
period, with a progressive movement of U into decaying tissue. µSXRF
maps showed the micrometer-scale distribution of Ca, Mn, Fe, Ni, and U
in roots of willow (Salix nigra L.) growing on a former radiological
settling pond, with U located outside of the epidermis and Ni inside the
cortex. X-ray computed tomography (CMT) of woody tissue of this same affected
willow showed that small points of high Ni fluorescence observed previously
are actually a Ni-rich substance contained within an individual xylem
vessel. IJoSXRF and x-ray absorption near-edge spectroscopy (XANES) linked
the elevated Se concentrations in sediments of a coal fly ash settling
pond with oral deformities of bullfrog tadpoles (Rana catesbeiana).
Se distribution was localized within the deformed mouthparts, and with
an oxidation state of Se ( -ll) consistent with organo-Se compounds, it
suggests oral deformities are caused by incorporation of Se into proteins.
The range of tissues analyzed in this study highlight the applicability
of synchrotron X-ray microspectroscopic techniques to biological tissues
and the study of metal(loid) bioavailability.
Keywords: Biological tissue, micro-XANES, nickel, selenium,
synchrotron x-ray fluorescence, uranium, x-ray fluorescence microtomography
SREL Reprint #2856
Punshon, T., B. P. Jackson, A. Lanzirotti, W. A. Hopkins, P. M. Bertsch and J. Burger. 2005. Application of synchrotron X-ray microbeam spectroscopy to the determination of metal distribution and speciation of biological tissues. Spectroscopy Letters 38:343-363.
