USE OF SCALING TO QUANTIFY VARIABILITY OF HEAVY-METAL SORPTION ISOTHERMS

Sorption isotherms of heavy metals in soil often vary strongly from pl ace to place in the field. Scaling might be useful to quantify the var iability of such functional relations. Application of scaling to sorpt ion isotherms requires a rule. In this paper the derivation of a scali ng rule for sorption isotherms, based on a hypothesis of 'sorption sim ilarity', and its application to cadmium sorption isotherms measured i n 25 fields on sandy soils are reported. Scale factors are calculated by least squares procedures. Scaling reduced the variation of the Cd i sotherms, expressed as sum of squares about an average, by about 86%, preserving the variation through the calculated scale factors. Scaling of sorption isotherms requires no specific equation to fit the sorpti on data. The aforementioned average should be calculated as scale mean because of the theoretical stringency of this approach.