Molecular scale speciation of first-row transition elements bound to ligneous material by using X-ray absorption spectroscopy

To develop a solid scientific basis for maintaining soil quality and formulating effective remediation strategies, it is critical to determine bow environmentally-important trace metals are sequestered in soils at the molecular scale. The speciation of Mn, Fe and Cu in soil organic matter has been determined by synchrotron-based techniques: extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES). We show the structural similarity between the surface complexes of Mn-II, Fe-III and Cu-II. These cations are bound to the surface through oxygen atoms. Each one presents a more or less tetragonal-distorted octahedral geometry. The use of X-ray absorption spectroscopy provides a relevant method for determining trace-metal speciation in both natural and contaminated environmental materials.