Fig. 3. Freundlich adsorption coefficients (K_f) for the adsorption and desorption of (a) p-aminobenzoic acid (pABA) and (b) sulfapyridine (SPY) in the presence of topsoil samples and particle-size fractions of an unfertilized and a fertilized loess Chernozem soil. Error bars not shown are smaller than symbols.