ATRAZINE SORPTION BY A MINERAL SOIL - PROCESSES OF LABILE AND NONLABILE UPTAKE

A microfiltration-HPLC technique which was recently introduced is appl ied to the study of the uptake of atrazine loro-4-(ethylamino)-6-(isop ropylamino)-s-triazine) by a mineral soil, Green Belt BG 843. The upta ke can be partitioned into labile and nonlabile contributions. Each pr ocess shows a saturation limit consistent with a ''complexation site'' model of atrazine binding. The indications of a definite and low stoi chiometry of uptake capacity is a key result of this analysis. The lab ile sorption capacity, theta(c), is 0.40 x 10(-6) mol g(-1). At 25 deg rees 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 upta ke is 8.8 x 10(-11) cm(2) s(-1), corresponding to a first-order rate c onstant of 9.6 x 10(-7) s(-1). Preliminary indications are that the ca pacity of nonlabile binding sites is < 10(-4) mol g(-1).