A study of the sorption kinetics of isoproturon on soil and subsoil: The role of dissolved organic carbon

The aim of this study is to investigate the role of dissolved organic colloids in the sorption of isoproturon to soils. Batch experiments were used to measure the rate of sorption of isoproturon onto soils down two soil profiles. Experiments were performed on soil that had been presoaked so as to release organic colloids from the soil. Results showed that dissolved organic matter competes with the solid phase as an sorptive surface for the isoproturon. The effect of dissolved organic matter appeared to be dependent upon the concentration present. A general sorption mechanism is proposed on the basis that the isoproturon is distributing between the soil, dissolved in solution and sorbed to organic colloids in solution. Within this framework the importance of external versus internal sorption sites on the organic matter and the possibility of specific sorbate-sorbent interactions are discussed.