Comments on the paper by Pierre D. Glynn

In the context of radionuclide migration from deep nuclear waste repositories, this letter critiques the findings of Glynn's research on plutonium and neptunium transport using a surface complexation model. The objective is to highlight flaws in the original study's conclusions regarding the transport dynamics of these elements. An analysis of the geochemical transport model indicates that the results may stem from limitations inherent in the numerical techniques employed, alongside unrealistic input data. The letter underscores that the modeling approach is not suitable for fractured crystalline rocks, which can worsen the applicability of the conclusions. The surface complexation model's advantages over simpler models are discussed, particularly regarding the allocation of sorption sites in stochastic environments. It is posited that when contaminants are present in low concentrations relative to sorbent availability, the models may eventually yield similar outcomes. Another critical point raised is the model's assumption of instantaneous equilibrium, which may misrepresent the sluggish desorption rates observed in natural rock environments. The letter concludes that the implications derived in the original study regarding the nuclide pulse behavior could be overly optimistic due to inadequacies in the modeling framework.