The formation of microscopic oil-mineral aggregates (OMA) has been linked to the natural removal of stranded oil in coastal marine environments and to the efficacy of surf washing (relocation of oiled sediment into the zone of wave action) as an oil spill remediation procedure. To predict the significance of this process in estuarine and freshwater environments, OMA formation was tested in the laboratory with seawater diluted to obtain a salinity range of 0-35. Quantification of the amount of oil incorporated into OMA shows that the extent of OMA formation is not significantly different from that of seawater for salinity values as low as 1.5-0.15 (1/20 to 11200 of pure seawater). The precise value of this threshold depends on parameters including oil type and the nature of the mineral present. Below this salinity threshold, there is a linear decrease in the amount of oil incorporated in OMA, to practically zero in distilled water. It is concluded that oil spill remediation by natural or induced OMA formation (i.e. surf washing) is applicable to marine, estuarine and possibly inland hyper-saline environments. Crown Copyright (C) 2003 Published by Elsevier Science Ltd. All rights reserved.