In order to estimate the possible influence of nitrilotriacetic acid (NTA) on the sorption of metals in the estuarine environment (Hamburg Hr./Elbe River Estuary as a critical example containing strongly polluted sediments) laboratory experiments were performed using an organic substrate, which was prepared from cell walls of the algae Scenedesmus quadricauda. While the concentration of sodium chloride, calcium chloride and magnesium chloride exhibits relative small effects on the sorption of copper, lead and zinc, a significant influence was measured for the sorption edges of cadmium and silver. For cadmium the combination of salinity and NTA affects lower sorption rates than does either one of both factors. On the other hand, the data for lead and copper indicate that with increasing salinity the mobilizing effect of higher NTA-concentrations is counteracted by the increase of calcium and magnesium. These findings suggest complex competition between various organic and inorganic ligands in the different states of estuarine mixing affecting metal interactions with particulate matter.