Characterisation of a second generation of European reference soils for sorption studies in the framework of chemical testing - Part II: soil adsorption behaviour of organic chemicals

In order to ensure the supply of European reference soils - the so-called EUROSOILS - to laboratories engaged in soil sorption studies, the European Commission's JRC introduced recently a second generation of these unique reference materials. In this paper the new EUROSOILS are compared to their precursors with regard to their adsorption behaviour of organic chemicals. To this end, the adsorption behaviour of 24 organic chemicals belonging to nine different substance classes were studied according to a procedure derived from the OECD test guideline 106 on adsorption/desorption. From the comparison of Freundlich isotherm data it was concluded that both versions of one reference soil feature the same adsorption behaviour. This is in agreement with the results presented in part I one of this paper where chemical composition and pedological properties were compared. In the case of EUROSOIL 1-4 almost identical adsorption coefficients could be determined despite the fact that analysis of soil organic carbon (C-org) revealed in some cases considerable differences in this parameter for both versions of one soil. EUROSOIL 5 showed a much higher adsorption potential than the previous version owing to a significantly higher organic carbon content - the only sorption relevant constituent in this soil. However, normalisation by C-org led to a good agreement of the derived K-oc data for both soil versions. Based on these observations, the applicability of the widely used K-oc-concept is discussed and the reference soil-set is proposed as a common basis for the achievement of a better comparison and quality of soil sorption data within the framework of chemical testing. (C) 1999 Elsevier Science B.V. All rights reserved.