Investigating Bioavailability of Militarily Relevant Metals Using Advanced Molecular Techniques.

The military currently faces the task of characterizing metal enriched soils and their effect on the surrounding environment.  Militarily relevant metals (lead, tungsten, and others) can have major impacts on human and ecosystem health, thus affecting environmental viability. Advanced geochemical studies are required to adequately understand these complex environmental systems.

Metal speciation is a critical geochemical data point missing from many bioavailability and environmental studies.  In many cases, metal speciation or complexation will control toxicity, bioavailability, and mobility of the element of concern.  Therefore, identifying metal speciation is critically important in toxicological studies, as well as for mobility and sorption investigations.  The US Army Engineer Research and Development Center Environmental Laboratory apply solid and liquid phase speciation tools to elucidate metal speciation in complex biogeochemical systems.  Synchrotron-based techniques provide the molecular-scale information needed to understand complex, environmentally relevant geodermic and biological media.  X-ray fluorescence (XRF) mapping coupled with X-ray absorption near edge structure (XANES) spectroscopy and X-ray diffraction (XRD) are in-situ techniques that determine elemental distribution and identify contaminant species for elements of concern.

The team has used these techniques to elucidate information about metal uptake, distribution and speciation on projects dealing with militarily relevant metals including tungsten (W) and lead (Pb).  Formation of metal rich granules in earthworms from Pb enriched soil is being examined.  Studies show earthworms will form mineral based granules with high concentrations of Pb and other metals found in the soils, thus rendering them nontoxic in their tissues and potentially limiting Pb mobility in natural settings.  Dermal and trophic transfer of W from plants and soil to gastropods is currently being studied using molecular techniques.  XRF data shows preferential W distribution in cabbage leaves, snail shells and tissues indicating there may be mechanisms for W transport and bioaccumulation within these materials.