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ABSTRACT. Detailed observations, mapping and sampling were conducted following an experimental spill of 15 m3 of crude oil adjacent to the coast at Cape Hatt, Baffi Island, N.W.T. The beach could not retain all of the oil that reached the shoreline, and as a result, one-third of the spilled oil was recovered in cleanup activities on the water, approximately one-third was lost to the atmosphere and to the Ocean and one-thrd remained stranded on the intertidal zone. The stranded oil was subject to natural cleaning processes during approximately 6 months of open-water periods from 1981 to 1983. Over this period the surface area of oil cover was reduced by approximately half, whereas estimates indicate that 80% of the oil initially stranded (5.3 m3) was removed. This natural removal of stranded oil occurred in a very sheltered environment. The reduction of the surface area and of the volume of oil resulted primarily from the physical processes associated with wave activity and ground-water leaching. By 1983 an asphalt pavement had developed in the upper intertidal zone on the beach-face slope. Total hydrocarbon concentrations of samples collected from the asphalt pavement indicated a significant increase in oil-in-sediment values in this zone to concentrations in the order of 2-5%. Oil removed from the beach was transported into the adjacent nearshore bottom sediments, where oil concentrations increased sixfold between 1981 and 1983. Physio-chemical weathering rates were relatively rapid immediately following the release of the oil, as the lower molecular weight (Cl to CIO) hydrocarbons evaporated. Subsequent physio-chemical changes were heterogeneous: weathering and biodegradation progressing slowly where oil-in-sediment concentrations exceeded 1%. The primary conclusion from the investigations undertaken to date is that oil is removed in substantial quantities from the intertidal zone even in such a sheltered, low-energy arctic environment. Similar changes should also be expected from comparable environments in lower latitudes. Key words: oil spill, natural oil weathering, asphalt pavement, beached oil RÉSUMÉ. On aeffectué des observations, des prises d'échantillons et des relevés détaillés à la suite d'un déversement expérimental de 15 m3 de pétrole brut, à proXimit6 de la côte du cap Hatt à l'île Baffin (T. N.-O.). La plage n'a pas pu retenir tout le pétrole qui a atteint le rivage, et il a fallu en enlever un tiers de la surface de l'eau lors d'op6rations de nettoyage. Un autre tiers environ a été éliminé par evaporation et par dissolution dans l'océan, et le dernier tiers est rest6 échoué sur la laisse. Ce p6trole &houé a kt6 soumis à des processus de nettoyage naturels pendant les périodes d'eau libre totalisant environ 6 mois entre 1981 et 1983. Pendant cette. période, la surface couverte de pétrole a diminué environ de moitié, et on estime qu'environ 80% du volume original du pétrole 6choué ( 5 3 m3) a été éliminé. Cette élimination naturelle du pétrole échoué s'est produite dans un environnement trks abrit...

The natural weathering and dispersion of oil stranded in the littoral zone depend on the type and volume of the oil and on the amount of available energy. Energy inputs can be biological, chemical, mechanical, or thermal; however, the single most important input appears to be from mechanical energy (winds, waves, tides, water levels, and ice). The residence time or persistence of stranded oils increases as mechanical energy levels at the shoreline decrease. The primary inputs of mechanical energy at the shoreline are due to wave action, and energy levels vary depending on the wind regime, fetch areas, and local exposure of a section of coast. In cold or polar climates, energy levels at the shoreline are reduced by the presence of ice on the sea or an ice foot on the beach. This review of the concepts associated with littoral processes, in terms of the mechanical dispersal of stranded oil, provides the basis for estimation of the persistence of oil on shorelines. Key words: petroleum (weathering, dispersal), coastal processes, wave energy, sea ice, ice foot, Canada

Investigations following the oil spill from the tanker ARROW in Chedabucto Bay, Nova Scotia, in 1970 have focussed on the physical and chemical degradation of the Bunker C oil in different littoral environments and on the effects of sediment removal to restore polluted beaches. Natural processes have restored the beaches effectively on coasts exposed to wave activity. In sheltered, low-energy areas, the oil has undergone relatively little change over the 3-year period and is still present in the littoral zone. The removal of contaminated sediments from exposed beaches has not caused major changes but has resulted in permanent retreat of the beach crest in areas of limited sediment supply.

Oil spill research and development has involved a large number of experiments to evaluate the effectiveness and the effects of marine shoreline protection and cleanup techniques. Considerable knowledge has accumulated from laboratory and wave tank studies, and there have also been a number of field experiments, in which oil was intentionally spilled on shorelines under controlled conditions. This review summarizes those field experiments, which are grouped in five major habitat types: rocky intertidal, cobble/pebble/gravel, sand/mud, saltmarshes, and mangroves/seagrasses. Tables included in the paper itemize the oil type and volume, location and substrate character, number and size of plots, response techniques tested, and referenced publications. This information is then used to combine understanding of the effectiveness of cleanup with understanding of the ecological effects of cleanup methods, compared with those of untreated oil. It is very difficult to achieve this type of information and understanding from toxicity testing or from spills of opportunity.