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The influence of humate formation on the adsorption of various ions on kaolinite and amorphous silica was studied using the multitracer technique, i.e., the simultaneous application of a variety of radioactive tracers. The technique simultaneously provided the solid-aqueous distributions of 32 elements, namely, Be, Na, Sc, V, Cr, Mn, Fe, Co, Zn, Ga, As, Se, Rb, Sr, Y, Zr, Tc, Ru, Rh, Ag, Te, Ba, Ce, Pm, Eu, Gd, Tm, Yb, Lu, Hf, Re, and Pt, in the absence and presence of humic acid. Speciation calculations under our experimental conditions were also conducted for 19 elements among them, using our previous results on the stability constants of their humate complexes. Comparison of the pH dependences of each element and humic acid dissolved in the aqueous phase enabled us to evaluate the interaction between them. With the aid of the speciation calculation, we discussed the predominant species that would …