APPLICATIONS OF X-RAY-ABSORPTION FINE-STRUCTURE SPECTROSCOPY TO SOILS

Determining the local chemical environment of a species is often a nec essity for evaluating its reactivity in the environment. However, obta ining direct molecular-level information is often problematic and may only be possible with severely invasive techniques. We discuss the phy sical and chemical aspects of x-ray absorption fine structure spectros copy (XAFS) and its application in soils. This technique can determine the local chemical and structural surroundings of a particular elemen tal species in soil and water or other natural systems, without the ne ed to subject the sample to a foreign atmosphere. Electronic informati on and a fingerprint of the x-ray absorbing element's local environmen t is provided with XAFS and can be used to determine the speciation of an element in media like soils. Precise structural information (bond distances within 0.02 Angstrom) can also be ascertained with this meth od, although this precision is often difficult to obtain in heterogene ous materials. Nevertheless, XAFS is a method that can contribute sign ificantly to our knowledge of soils and soil reactions.