EFFICIENCY OF PEDOTRANSFER FUNCTIONS DESCRIBING CADMIUM SORPTION IN SOILS

摘要

Pedotransfer functions based on general purpose Freundlich isotherms (GPF) were derived for Cd using different combinations of input variables or development conditions. The models match the criterion of flexibility as they were derived from data of 497 soil samples, which had strongly varying soil characteristics. The prediction efficiency of the approaches was investigated by comparison of measured and simulated sorption data for 124 independent soil samples. The parameterisation of the GPF shows that models derived from data of batch sorption experiments by multiple linear regression achieve best goodness-of-fit and statistical consistency. The use of extraction data or nonlinear regression analysis results in greater deviations from the statistical optima. The best overall performance considering parameterisation and validation was observed for the models including (a) the variables 'proton activity', 'clay content', 'soil organic carbon', 'sum of dithionite-extractable Fe-and Mn-oxides' or (b) the variables 'proton activity', 'potential cation exchange capacity', 'sum of dithionite-extractable Fe- and Mn-oxides'.