A study of the adsorption kinetics of isoproturon on soil and subsoil

The aim of this study is to investigate the mechanisms of adsorption of isoproturon onto soil and to produce predictive relationships between the adsorption rate constant and the measurable properties of the soil. A batch technique was used to measure the rate of adsorption of isoproturon onto soils down a single soil profile. The major results were: 1. (i) simple predictive relationships could not be derived;2. (ii) use of linear-free energy relationships showed up the differences between different techniques for measuring adsorption rate constants; and3. (iii) the linear free energy plot of the data suggested that specific sorbate-sorbent interactions were an important adsorption mechanism for non-hydrophobic compounds in a batch methodology. An adsorption mechanism is proposed that suggests that adsorption of isoproturon to soils is the distribution of the compound between three phases — dissolved in solution, bound to insoluble matter and adsorbed to organic colloids in suspension.