Adsorption and desorption kinetics of diflubenzuron and fenitrothion in two different boreal forest soils

Abstract Adsorption and desorption of two insecticides, diflubenzuron (DFB) and fenitrothion (FEN), were studied by batch equilibrium method under laboratory conditions (pH 5.5, 20°C), using an organic soil (soil 1) and a silty clay loam soil (soil 2), collected from a boreal forest in northern Ontario, Canada. Adsorption parameters were calculated using the linear, Freundlich and Langmuir equations. Maximum amount adsorbed and the time required for maximum adsorption of DFB were 88 μg/g and 18 h (soil 1), and 73 μg/g and 24 h (soil 2), respectively. Corresponding values for FEN were 92 μg/g (soil 1) and 81 μg/g (soil 2), and maximum adsorption time for both soils was 30 h. DFB was more strongly adsorbed to both soils compared to FEN, however between the two soils, soil 1 showed stronger affinity for the chemicals than soil 2. The KD, KF and n values corroborated these findings. The Langmuir model showed deviation, probably due to heterogeneity of the soil surface and multi‐layer adsorption. Desorption st...