Sam Webb

Synchrotron Based X-Ray Techniques for Environmental Remediation

Sam Webb

Stanford Synchrotron Radiation Laboratory

To effectively design and evaluate many types of remediation scenarios, it is often desirable to examine the chemical speciation of toxic metals. Synchrotron radiation is a useful tool for examining in situ both metal speciation and distribution in a wide variety of environmentally relevant samples. X-ray absorption spectroscopy (XAS) is an element specific technique which evaluates the local oxidation states and probes the neighboring atoms around the absorbing atoms. Using focusing optics, the x-ray beams can be focused to a size on the order of several microns, giving chemical information on a spatial scale which is useful to many environmental and biological systems. Several examples of how XAS can be used in practice will be discussed, looking at the potential of biologically oxidized manganese for uranium attenuation and sequestration, and the mechanism of hyper-accumulation of arsenic in plant biomass.