ATRAZINE SORPTION IN FIELD-MOIST SOILS - SUPERCRITICAL CARBON-DIOXIDEDENSITY EFFECTS

Supercritical carbon dioxide (SF-CO2) has been recently introduced for use in determining sorption coefficients of atrazine -N-ethyl-N'-(1-m ethyl)-1,3,5-triazine-2,4-diamine) in field-moist soils. In this study we determined the effects of SF-CO2 density modification on atrazine- soil sorption coefficients. As the density of SF-CO2 increased, the SF -CO2 soil/water partition coefficient (K-d) decreased. K-d values for the first desorption equilibration (K(d)D1) obtained with the SF-CO2 t echnique at an SF-CO2 density of 0.25 g mL(-1) were linearly related t o soil organic carbon content, clay content, and batch Freundlich coef ficients (Kf values). The log of K, for each soil was linearly related to the log of the SF-CO2 density for densities 0.25 through 0.45 g mL (-1). The SF-CO2 Kd value predicted using the batch K-f/SF-CO2 K-d rel ationship obtained in this study, and an experimental batch K-f value for a Minnesota (USA) soil from the literature, was consistent with th e SF-CO2 K-d values predicted using organic carbon and clay content re lationships obtained from this study. (C) 1998 Elsevier Science Ltd.