The gas absorption rate in a stirred cell with plane interface has often been found to be increased by suspended activated carbon particles. The effect is usually explained by an additional adsorptive transport mechanism for the gas ("shuttle" or "grazing" effect). In this study, however, the effect is observed only when surface active contaminants are present. Fingerprints and the non-ionic surfactant isodecanol heptaethoxylate are considered. By adding activated carbon, the liquid-side mass transfer coefficient can be gradually increased up to the value observed in surfactant-free water. When using different gases, the apparent physical enhancement, effect is independent from the respective adsorption capacity of activated carbon. Therefore, adsorptive transport is negligible whereas the actual effect of activated carbon is to "graze" surfactant that otherwise induces surface rigidity. (c) 2006 Elsevier Ltd. All rights reserved.