Effect of temperature on adsorption-desorption behaviour of triazophos in Indian soils

The present study investigated the adsorption-desorption behaviour of triazophos on Indian soils at 10, 20 and 40 degrees C using batch equilibrium technique. Results revealed that adsorption isotherms were explained better by Freundlich model and adsorption coefficient (K-f) decreased with increase in temperature indicating that adsorption was affected strongly by temperature. Moreover thermodynamic analysis showed that triazophos adsorption onto soil was spontaneous, exothermic and might have occurred through chemisorptions, hydrogen bonding or ligand-exchange interactions. Desorption results depicted that nearly 90% of the pesticide amount adsorbed by soil was retained by it at 10 degrees C and the amount decreased with increase in temperature. Thus, the pesticide has a potential to contaminate surface and ground water at higher temperature due to weak adsorption on tested soils and release of more adsorbed pesticide during desorption with water. At temperature below 20 degrees C, pesticide became almost immobile and therefore soil remediation may be required. The study highlights the importance of temperature in regulating the application of triazophos in soil.