Sorption behaviour of Cypermethrin in selected Agricultural soils from Kakira, Lugazi and Kalangala farming areas in Uganda

Abstract

This study determined sorption kinetics and sorption equilibrium of cypermethrin on soil samples from sugar cane plantations in Kakira and Lugazi, and an oil palm tree growing area (Kalangala) in Uganda. Cypermethrin sorption kinetics in the above soils was best described by Pseudo-second order kinetic model, reaching equilibrium before 24 hour. The sorption isotherms were well described by the linear model with linear correlation coefficient (R2) values close to 1. The linear adsorption distribution coefficient (KD) values of cypermethrin in the soil ranged from 1.209 to 3.477 mL g-1 for Lugazi, 0.509 to 2.711 mL g-1 for Kakira and 0.601 to 2.350 mL g-1 for Kalangala. The low values of KD are in agreement with the low organic carbon content in the soil samples (0.01-0.05 g g-1). When the KD values were normalized to account for the influence of organic carbon content in the soil, the average organic carbon partition coefficient (KOC) values were 60.94, 52.09 and 83.88 mL g-1 for Lugazi, Kakira and Kalangala, respectively. The KOC values indicate that cypermethrin is weakly adsorbed onto the soils from Kalangala, Kakira and Lugazi, and highly mobile suggesting that cypermethrin could be easily leached.