Sorption of cadmium and lead in a Dystrophic Red Latosol amended with lime and phosphate

Abstract

The objective of this work was to evaluate the sorption of cadmium and lead in samples of a Dystrophic Red Latosol under the effect of lime and  phosphate. The soil was sampled at 0-0.20 m layer, sieved, and incubated with lime and/or phosphate, so that four sample conditions could be compared: control (without lime and without phosphate), with lime, with phosphate, and with lime and phosphate. Sorption was evaluated by the Langmuir and Freundlich isotherms. Soil samples of 1 g of each condition were shaken during 48 hours with 25 ml of solution with 0; 0.012; 0.030; 0.070; 0.078 or 0.275 mmol L^-1 of Cd and 0; 0.021; 0.041; 0.099; 0.160 or 0.312 mmol L^-1of Pb. After agitation and centrifugation at 500 g, the Cd and Pb supernatant concentrations were determined. Lime and phosphate applied either isolated or together increased both Cd and Pb sorption. Sequence of sorption was: control < lime < phosphate < lime and phosphate. Regardless of the sample condition, sorption of Pb was higher than Cd.