Atrazine sorption by a mineral soil: Processes of labile and nonlabile uptake

A microfiltration-HPLC technique which was recently introduced is applied to the study of the uptake of atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) by a mineral soil, Green Belt BG 843. The uptake can be partitioned into labile and nonlabile contributions. Each process shows a saturation limit consistent with a ''complexation site'' model of atrazine binding. The indications of a definite and low stoichiometry of uptake capacity is a key result of this analysis. The labile sorption capacity, theta(c), is 0.40 x 10(-6) mol g(-1). At 25 degrees C an equilibrium constant, K-1, for the labile sorption is 3.0 x 10(4) M(-1), and the apparent diffusion coefficient for nonlabile uptake is 8.8 x 10(-11) cm(2) s(-1), corresponding to a first-order rate constant of 9.6 x 10(-7) s(-1). Preliminary indications are that the capacity of nonlabile binding sites is < 10(-4) mol g(-1).