30th Annual SSRL Users' Meeting — October 9-10, 2003

Examples of the Application of Mirror-based Hard X-ray Microprobe Techniques in the Earth and Environmental Sciences

A. Lanzirotti and S. R. Sutton

Consortium for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637

The ability of high-energy synchrotrons to produce highly collimated, intense x-ray radiation makes them ideal sources for x-ray microprobe analysis of earth and environmental materials. Such synchrotron based x-ray microprobes allow for trace element quantification (x-ray fluorescence), chemical speciation determination (x-ray absorption spectroscopy), and phase identification (x-ray diffraction). In the design of such instruments Kirkpatrick-Baez mirrors have proved particularly useful for producing x-ray microbeams because of their achromaticity, photon density gains in excess of 104, and long working distances (centimeters). In the earth and environmental sciences, instrument development and utilization has been driven by the need for the determination of material compositions, structures, oxidation states, and bonding characteristics with trace element sensitivity and micrometer spatial resolution. A number of examples will be discussed that show flexibility of this technique, but two particular examples will be highlighted. These include the use of x-ray fluorescence analysis and x-ray absorption spectroscopy in evaluating the contaminant history of Ni, U, and other metals within annual rings of willows ( Salix nigraL.) from a former de facto radiological settling basin (Punshon, et al., 2003). We'll also examine how x-ray microbeam compositional imaging, absorption spectroscopy, and diffraction techniques have been used to quantify the co-existence of As3+ and As5+ in oxidized rims of roaster iron oxide grains in mine tailings from gold mining activities in the Yellowknife area (Canada).