Fig. 3. Isotherms representing pesticide sorption by reference smectite clays (SWy-2 and SAz-1) and the corresponding humic acid (HA)-clay complexes. (A) Sorption of 4,6-dinitro-o-cresol by Ca-HA-SWy-2/Ca-SWy-2, (B) Ca-HA-SAz-1/Ca-SAz-1, (C) sorption of dichlobenil by Ca-HA-SWy-2/Ca-SWy-2, and (D) Ca-HA-SAz-1/Ca-SAz-1. The lines represent the predicted curves obtained by summing up individual and independent contribution of humic acid and smectite clays to pesticide sorption.