Sorption and desorption of atrazine on soils: The effect of different soil fractions

Abstract

The study of atrazine (AT) sorption and desorption was carried out, employing three Brazilian soils (Typic Acrudox, Typic Argiudoll and Oxic Argiudoll), using horizons A and B, as well as their clay fractions – natural clay, clay after H2O2 treatment, clay after iron removal and after treatment to concentrate iron oxides. A contact time of 12 h was defined as adequate for sorption studies. Sorption and desorption curves were adjusted by the Freundlich equation, and satisfactory linear responses were observed, between 0.8332 and 0.9998 for the sorption process. Multiple regression analyses were performed considering the mineralogy, organic carbon content, specific surface area and texture of the soils, and the Freundlich parameter Kf. The principal influence for AT sorption was attributed to organic carbon content and physical bonding on quartz for soil samples. Positive correlation with goethite was observed for clay fractions. The Kf values for sorption (Kf(S)) obtained for soil samples were between 0.60 and 3.9, and for clay fractions were between 1.90 and 5.30, suggesting an important role of the mineral phase in the sorption of AT. Environmental risks of groundwater contamination were evaluated using the partition coefficient normalized by the soil organic carbon content (Koc), hysteresis index (HI), groundwater ubiquity score (GUS) and leachability index (LIX). Both horizons for the three soils presented leaching potential for AT based on GUS and LIX parameters.