COMPORTAMIENTO ADSORTIVO-DESORTIVO DEL LINDANO EN UN SUELO AGRÍCOLA

SUMMARY The purpose of this work was to evaluate the adsorptive- desorptive behavior of the pesticide lindane on an agricultural soil rich in organic matter, using the differential coefficient of hysteresis concept (CHPoggi). Lindane showed a linear adsorp- tion, given by the isotherm q= 3.91·C, and a Langmuir-like de- sorption with q= (32.9·C)/(1+1.11·C). The CHPoggi concept was further extended for the mixed case that consisted of linear ad- sorption and hyperbolic (Langmuir) desorption by the deriva- tion of a simple, algebraic equation based on the isotherm co- efficients given by CHPoggi= a·b/kl , where a: maximum capacity of the desorption curve, b: desorption curve shape coefficient, and kl: coefficient of the linear adsorption isotherm. Values of CHPoggi of 8.4 and 6.6 were obtained using the simple algebraic equation and the ratio of the slopes of tangents to both iso- therms, respectively. This indicated a reasonable agreement be- tween both calculation methods, considering the experimental errors. Also, it suggests that the hysteresis between lindane and agricultural soil was moderate to high.