Species on porous media surfaces exposed to aqueous solutions can still not yet be determined unambiguously. The influence of these ambiguities on contaminant transport needs to be understood. Here methods of multicomponent chromatography are presented that allow to visualize the effects of the ambiguities. The Riemann problem is solved to a large extent based on the mathematics of non-linear hyperbolic differential equations, before the problem is handed over to the computer. Since thereby the

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... computational efforts are kept compatible with the corresponding limitations in a chemical laboratory, this method has been used for decades in chemical engineering. The method is illustrated for various multicomponent isotherms, e.g. the one underlying surface complexation models as implemented in the MINEQL family of programs.