Fig. 3

Normalised cation diffusion coefficients D _erw for Na⁺, Sr²⁺ and Cs⁺ plotted as a function of the normalised sorption capacity κ = ρ _bd K _d /ε. Small symbols literature values for tracers compiled by Gimmi and Kosakowski (2011); lines model (Gimmi and Kosakowski 2011). For Cs, two lines are drawn according to two subsets of the data as identified in Gimmi and Kosakowski (2011): thicker line for data obtained at comparably high (but constant) Cs background concentrations or for samples without illite, thinner line for data obtained at Cs trace concentrations in samples containing illite (thus probably strongly influenced by frayed edge sites). Large symbols and shaded area D _erw derived from results of Mont Terri field experiments (Van Loon et al. 2004b; Wersin et al. 2008, partly re-analysed). In the field experiments, the Cs concentration was not constant: initially comparably high, then quickly decreasing to lower values. This leads to K _d values varying in time and space due to non-linear (multi-site) sorption. The large symbol for Cs is drawn at the average K _d value, the shaded area encompasses the relevant K _d range