Modeling of sulfate adsorption on andisols for implementation in the SAFE model

Sulfate adsorption models were investigated in this study to simulate the p H dependence of SO42- and H+ adsorption on Andisols and thereby show the ef fects on acidification and recovery processes of Andisols, An extended cons tant capacitance model (ECCM), which assumed protonation of surface -OH gro ups and outer-sphere complexation of SO42-, proved valid to simulate SO42- and HS adsorption on Andisols when evaluated using batch experiment data of SO42- and base cation adsorption at pH 4 to 5 and low ionic strengths. Acc ording to the ECCM calculation, SO42- adsorption was reproduced by an empir ical equation using SO42- and H+ concentrations and H+ adsorption was appro ximated by another empirical equation using pH and SO42- adsorption. Since these two empirical equations are quite simple, they will be an efficient S O42- adsorption submodel in SAFE, the dynamic soil chemistry model to simul ate the soil acidification and recovery processes.