Regionalization of sorption capacities for arsenic and cadmium

To fulfill the purpose as a sink for trace elements, soils must not be over loaded with As and Cd. Therefore, it is necessary to get knowledge of the s orption capacities of soils on a regional scale. The determination of these sorption capacities for large areas is, however, impeded by the great expe nditure of laboratory work involved. With data presented here retention cap acities for cadmium and arsenic from routinely determined soil parameters a re estimated. In batch experiments the sorption behaviour of 40 soils from the area of Freiberg/Saxony in Germany was examined. The obtained sorption isotherms from the laboratory were fitted to the Freundlich equation (S = k *C-m). The two constants (k, m) of this equation were used for multiple lin ear regression to correlate the sorption capacity and the soil parameters, namely clay content, pH value, total organic carbon, and dithionite extract able Fe contents. Due to long lasting ore mining of Freiberg there exist hi gh background levels in that area for the two surveyed elements As and Cd. Therefore, this study offers two different mathematical procedures to take these contaminations into account. Thus the experimental data were correcte d before they were fitted to Freundlich and pedotransfer equations were det ermined. Using the transfer equation, parameter k and m for cadmium sorptio n could be estimated with statistical certainties of 91% and 61% (adjusted R-2), respectively, whereas the predictability for the arsenic sorption is not practicable because achieved R-2 values are very low (17% and 7%).