"ATRAZINE ADSORPTION-DESORPTION BEHAVIOR IN DAREHASALUIE KAVAR CORN FIELD SOIL "

Abstract

Adsorption desorption behaviors of widely applied atrazine soil were studied, employing a batch technique as a case study in Darehasaluie Kavar corn field in Fars Province in 2005. Samples were collected into 0 to 20 cm soil depth, where was cultivated under a crop rotation (corn-wheat) during the past 10 years. Sorption kinetics exhibited two phenomena: an immediate rapid sorption (1.31 µg/g soil after 12 hours) followed by a slow sorption process (1.37 µg/g soil after 24 hours). Desorption behavior of atrazine was similar to its adsorption, but at a very slower rate. Atrazine desorption efficiencies were much less effective and incomplete even after a long equilibration time (only 9.16% after 96 hours). The adsorption-desorption rate for most of the time was positively related to the amount of applied atrazine and the time required for equilibration (P<0.01). Desorption data exhibited hysteresis phenomena. Atrazine adsorption data described well according to Freundlich (r2=0.95), Langmuir (r2=0.82) and Temkin (r2=0.84) isotherms. However, the fit to Freundlich adsorption model in a non linear form (1/n <1) was closer than the others. Desorption isotherm could be well described by the Temkin (r2=0.96) and Freundlich (r2=0.92) isotherms, but the fit to Temkin model was closer than that of Freundlich.