Mobility, Geochemistry, and Speciation of Tungsten

摘要

Tungsten metal is used in many industrial, military, and consumer applications, and interest in its biogeochemistry is increasing partially due to its potential mobility and biological effects. Recent studies have investigated the geochemistry of tungsten from the laboratory to field scale, to determine its mobility and toxicity. Tungsten exists in most environmental matrices as the soluble and mobile tungstate anion, although polymerization to form poly- and heteropoly- tungstates has been shown to occur. The current study investigates tungsten speciation in soil using size exclusion chromatography (SEC) interfaced to Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to separate and quantify monomeric and polymeric tungsten species. Direct infusion Electrospray Ionization Mass Spectrometry (ESI-MS) is also used to identify the specific polymeric species present in the soil. Finally, solid phase speciation has been conducted using XANES and XAFS spectroscopy utilizing specialized synchrotron techniques. Poly- and heteropolytungstate species have been identified in environmental matrices using these techniques, and the variable speciation observed directly affects biogeochemical processes, such as mobility, sorption, and toxicity.