On the incorrect derivation and use of in-situ retardation factors from natural isotope profiles

The characterization of the retardation of radionuclides during their transport by deep groundwaters is complex, time-consuming and, in many cases, inherently limited by technical problems. The stated goal of many natural analogue studies is thus the direct quantification of solute retardation in-situ in relevant geological environments. This paper reviews the claims for a methodology for determining in-situ retardation factors from a mathematical deconvolution of multiple radioisotope measurements of natural decay series elements. It is concluded that the assumptions involved in development of the mathematical approach are geochemically inconsistent and inapplicable to most geological systems of interest. Misapplications of this model are identified and the dangers of accepting its nonsensical output are discussed. (orig.)