The enthalpies of adhesion of water and four organic solvents (heptane, octanol, diethyl ether and methyl isobutyl ketone (MIBK)) onto solids (silica, aluminium, iron and manganese oxides, calcium carbonate, kaolinite and a mixture of clays) representative of natural riverine suspended matter are measured by (micro)calorimetry. A systematic comparison of the enthalpy values yields an insight into the physicochemical processes that contribute to the interactions of solvents with solids. In all cases, following pretreatment by low heat, surface hydroxyl groups dominate over the other reactive surface sites and mask the intrinsic characteristics of the bare solid. Hydrogen bonds then become the main contributing factor to the solid-liquid interaction whatever the polar solvent used. From the differences between the enthalpies of adhesion, the numbers of surface hydroxyl groups on the solid surfaces are estimated. © 1995.