Sorption and transport characteristics of cadmium and dissolved natural organic matter with a coarse loamy soil

Abstract

Various humic substances were reacted with a coarse loamy soil in both batch studies and column experiments. Solution pH was not buffered, rather monitored to more closely approximate a "real life" scenario. Humic substances were also reacted with soil that had been pre-saturated with various concentrations of cadmium nitrate solution. The batch experiments were characterized by interference from antecedent natural organic matter in the soil, causing high nonlinearity in the data. Humic substance sorption in the column experiments was characterized by early breakthrough of a small fraction, followed by long extended tailing. Complete breakthrough was never observed in any of the column studies. Sorption phenomena is believed to be primarily controlled by the structural configuration of the humic substances, with solution pH and the valence of cations in the electrolyte solution having the greatest effect on sorption. Implications to humic substance transport in natural systems will be discussed.