Parameterization and regionalization of Cd sorption characteristics of sandy soils. I. Freundlich type parameters

Abstract

AbstractCd sorption isotherms (n = 24) were established for arable, sandy soils of the ‘Fuhrberger Feld’ catchment area northeast of Hannover (Germany) using 0.01 Mc Ca(NO3)2 solution with Cd additions ranging from 0 to 44 μMc Cd. Alternative fractions of initially (prior to analysis) sorbed Cd (S0) were added to the amount sorbed during the experiments. The Freundlich equation was fitted to the resulting isotherms. The obtained retention parameters k and M varied with respect to the different S0 fractions. Isotherms corrected with CdEDTA as S0 fraction were nonlinear in their log‐form. The highest degree of log‐linearity is obtained if S0 is characterized by 40% of the agua regia extractable Cd. The corresponding k values ranged from 36 to 1275 g1‐M LM kg−1 (mean 338 g1‐M LM kg−1, cv = 92%). The Freundlich exponent M showed less variation (0.7 to 1.1, cv = 12%) with a mean of 0.88. Functions based on these parameters predicted Cd concentrations in Ca(NO3)2−soil suspensions well (r2 = 0.96) but were hardly related to Cd concentrations of ‘fresh’ soil solutions (r2 = 0.20).