Kinetics and equilibria of Metribuzin sorption on model soil components

Sorption to solid phase materials is known to significantly affect the transport, bioavailability and ultimate fate of organic contaminants in soils and sediments. In order to develop a complete description of the fate of these compounds, it is necessary to understand both equilibrium interactions and rates and mechanisms of the sorption processes. The object of the present study was to investigate both these factors with respect to the sorption of metribuzin on model soil components, including the clay minerals kaolinite and montmorillonite, amorphous iron and aluminum hydrous oxides and humic acid. In all cases, uptake followed a similar course; there was a very rapid initial sorption process followed by continued uptake at a much slower rate. Rate constants for the slow sorption were smallest for the clay minerals, intermediate for the hydrous oxides and greatest for humic acid. Labile sorption capacities for metribuzin on the humic acid and clay minerals were also determined; the organic material had ...