ADVANCES INISOTOPIC DILUTION TECHNIQUES IN TRACE ELEMENT RESEARCH: A REVIEW OF METHODOLOGIES, BENEFITS, AND LIMITATIONS

New insights into factors controlling element bioavailability and mobility in soils have been achieved through the use of isotopic dilution methods. With the advent of robust and relatively simple analytical techniques able to accurately determine stable isotope ratios, the future use of isotopic dilution methods is expected to continue to expand. In both theory and practice, the E- and L-value isotopic dilution methods appear relatively simple to apply. However, this simplicity is deceptive: in reality, there exist a number of pitfalls that can result in collection of flawed data or inappropriate data interpretation. With a focus on trace elements, this chapter reviews studies that have applied isotopic dilution techniques to examine various aspects of soil chemistry and bioavailability, provides guidance on conducting isotopic dilution experiments, and discusses potential future applications for these techniques. The various pitfalls that may be encountered, including precipitation artifacts, colloidal interferences, and labile redox state effects, as well as how to identify and avoid such pitfalls, are also described.