Influence of humic substances on the aquatic adsorption of heavy metals on defined mineral phases

The distribution of heavy metals in the aqueous phase of aquifers is strongly dependent on the kind of solid phase and on the presence of dissolved organic matter. Batch experiments were performed to investigate the phase distribution of Cd, Pb, and Cu using Quartz, Potassium Feldspar, Sodium Feldspar, Kaolinite, Calcite, and Fe/Mn-coated Quartz sand as mineral phases. Natural organic matter (NOM) from a brown water lake was used to study its influence on the phase distribution of the metals. From the experimental results, Freundlich isotherms were calculated. They turned out to be suited for a description of the heterogeneous systems. Despite the obvious limitations of mechanistic interpretation, NOM increased the dissolved fraction of Cu and Pb, and decreased that of Cd.