Sorption, Desorption and Mobility of Microencapsulated Chlorpyrifos in Two Typical Soils

The sorption, desorption, and mobility of microencapsulated chlorpyrifos (CPF-MC) in two typical soils, namely, silt loam and sandy, were investigated in this study. Sorption/desorption experiments were carried out by using the batch equilibration method. Results showed that the sorption isotherms of CPF-MC and emulsifiable concentrate of chlorpyrifos (CPF-EC) in silt loamy soil were similar. However, a considerable difference was observed in the sorption isotherms of two chlorpyrifos (CPF) formulations in sandy soil. The amounts of CPF desorbed from two soils in four desorption steps decreased sequentially in CPF-EC treatments, while the desorbed amounts remained stable in CPF-MC treatments. Hence, the sorption/desorption processes of CPF-EC were mainly controlled by soil affinity to CPF. However, these processes of CPF-MC were affected by the release rate of CPF from capsules. The mobility of two CPF formulations in soil was estimated in vertical columns packed with soils. Results showed that there was leaching of CPF-EC in silt loam column, whereas CPF-MC was not vertically mobile in silt loam column under the same leaching conditions. However, in column with sandy soil, the percentage of CPF-MC leaching from the column was 86.54%, which was higher than the 73.75% that leached from the column in the treatment with CPF-EC.

Automated summary

This study investigated the sorption, desorption, and mobility of microencapsulated chlorpyrifos (CPF-MC) in two typical soils. The results showed that the sorption isotherms of CPF-MC and emulsifiable concentrate of chlorpyrifos (CPF-EC) in silt loamy soil were similar, while there was a considerable difference in sandy soil. The desorption processes of CPF-EC were controlled by soil affinity to CPF, while CPF-MC desorption was affected by the release rate of CPF from capsules. In terms of mobility, CPF-EC was found to leach in silt loam soil, but CPF-MC was not vertically mobile; in sandy soil, the leaching percentage of CPF-MC was higher than that of CPF-EC.