ATRAZINE SORPTION BY A MINERAL SOIL - EFFECTS OF SOIL SIZE FRACTIONS AND TEMPERATURE

Equilibrium, kinetics, and mechanism of sorption of the herbicide atra zine by a mineral soil (GB 843) have been studied with an on-line micr ofiltration-HPLC technique combined with a batch design. As a continua tion of our previous work, this paper presents the results of a study of soil size fractionation and the effect of temperature. The experime nts with soil size fractions revealed only relatively small changes in atrazine uptake. As expected, the experiments with varying temperatur e 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 ph ysisorption (Delta H degrees approximate to 0 kJ mol(-1)), while the n onlabile intraparticle diffusion was controlled by an activated proces s (E(a) = 89 kJ mol(-1)).