Atrazine sorption by a mineral soil: Effects of soil size fractions and temperature

Equilibrium, kinetics, and mechanism of sorption of the herbicide atrazine by a mineral soil (GB 843) have been studied with an on-line microfiltration-HPLC technique combined with a batch design. As a continuation of our previous work, this paper presents the results of a study of soil size fractionation and the effect of temperature. The experiments with soil size fractions revealed only relatively small changes in atrazine uptake. As expected, the experiments with varying temperature from 5 to 35 degrees C have shown a quite significant effect on the rate parameters of labile sorption (k(s1)) and intraparticle diffusion (K-d1 and D). However, the effect on the labile equilibrium constant was small. The resulting energetic parameters Delta H degrees and E(a) suggested that the labile uptake of atrazine may only involve weak physisorption (Delta H degrees approximate to 0 kJ mol(-1)), while the nonlabile intraparticle diffusion was controlled by an activated process (E(a) = 89 kJ mol(-1)).