Hexanoic(hex) and fulvic acid(FA), representing early and later stages of landfill leachate evolution, were examined for influence on trace metal adsorption by poorly crystallized kaolinite(KGa-2). Our experiments represented a model approach to examine possible reaction mechanisms in an environmentally important ternary metal-ligand-mineral surface system. Measured surface charge properties of KGa-2 were combined with binary and ternary system data in constructing a quantitative model of the system. In both ternary systems, the addition of ternary surface complexes(TSCs) to the models resulted in a satisfactory fit to the data. Our work suggests the strong possibility that TSC involvement in surface reactions of natural adsorbents may be a useful concept.