Lattice Location of Trace Elements Within Minerals and at Their Surfaces with X-ray Standing Waves

The x-ray standing waves generated by dynamical Bragg diffraction were used to directly measure lattice locations of trace elements within and at the surface of a mineral single crystal. These high-precision measurements were made on natural lceland spar calcite cleaved along the (10$\overline{1}$4) plane and reacted with a dilute aqueous lead solution. Within the bulk crystal, naturally occurring trace manganese was found within (10$\overline{1}$4) planes, consistent with its substitution for calcium. At the crystal surface, sorbed lead was found to be highly ordered and mostly within (10$\overline{1}$4) planes. This demonstrates a powerful application of synchrotron radiation in the earth and environmental sciences.