Abstract In volcanic soils of the Solofrana valley (south-western Italy), contamination by Cr and Cu occurs as a consequence of agricultural practices and surface deposition of polluted river sediments by periodic floods. In this study, the metal distribution in micromorphological features and clay fractions ( − 1 ). Both Cr and Cu are present in the subsurface infillings with concentrations of 273 and 243 mg kg − 1 . In deeper horizons, the fragments of stratified fine textured alluvial deposits, incorporated in the soil matrix, contain low concentrations of both metals (13–63 mg kg − 1 for Cr and 18–24 mg kg − 1 for Cu), suggesting that Cr and Cu migration, in colloidal or ionic form, is restricted to a limited distance. The contribution of the clay fraction (