Accidental releases of oil to the marine environment can reach sensitive shorelines resulting in a wide range of environmental impacts. Chemical dispersant is a response tool employed to minimise damage to coastal ecosystems by facilitating dispersal of oil slicks before they reach shores. However, chemical dispersants may increase entrainment of hydrocarbons into coastal sediments following an oil spill, resulting in higher hydrocarbon residence times in sediments. Here, the effect of dispersant concentration on the entrainment capability of hydrocarbons in permeable coastal sands from North East Scotland (United Kingdom) was evaluated. Hydrocarbon entrainment into sands was facilitated by dispersant application at concentrations below manufacturer-recommended dosage. Percolation of water-soluble hydrocarbons beyond 10 cm deep was not affected by chemical dispersant application and water-insoluble hydrocarbon concentrations increased with dispersant concentration. Results highlighted that the application of dispersant readily mobilised less water-soluble hydrocarbons through coastal sands but did not affect pore-water transport of more water-soluble hydrocarbons.
Bibliographical noteThe authors acknowledge Paul Hallett and Annette Raffan for granting access to and training on the tensiometer, respectively. Cruickshank Analytical Lab staff are acknowledged for assistance in carbon content analysis. The Marine Collaboration Research Forum is acknowledged for funding LJP's PhD project. BP are acknowledged for providing Schiehallion crude oil.