Fig. 6. 2,4-D adsorption isotherms on a linear scale for the sorption on quartz, calcite, and -alumina. Full symbols denote adsorption points where the pesticide solutions were added after equilibration of the water–mineral system. Open symbols denote adsorption points where the pesticide solutions were added directly to the dried mineral powder. The Freundlich constant (K_F) is given in (µmol/m²) (µmol/mL)^-n. Error bars indicate standard deviation (may be covered by the symbols).