FATE OF OIL IN THE SEA 

 Richard F. Lee 

 INTRODUCTION 



Millions of tons of petroleum enter the sea each year from marine trans- 

 portation, offshore oil production and coastal oil refineries, sewage outfalls, 

 natural seeps, and atmospheric fallout. Published estimates of the sources 

 and quantities of petroleum in the sea are available from several recent reports 

 (Ocean Affairs Board 1975, American Institute of Biological Sciences 1976). 

 The largest contributor (approximately 2 million tons/year) of petroleum to 

 the sea is marine transportation, which includes losses during normal ship 

 operations, oil spills resulting from accidents at sea, and spills during 

 operations at oil terminals. 



Crude oils and oil products can contain many thousands of compounds, 

 most of which are hydrocarbons, both aliphatic and aromatic. Minor components 

 include oxygen-, nitrogen-, and sulfur-containing compounds. After a spill, 

 a "slick" forms on the surface of the sea because of the low water-solubility 

 of most petroleum compounds. The fate of this slick depends on various bio- 

 logical, chemical, and physical processes which act to disperse or modify 

 it (Figure 1). The fate of oil in sediment and in the water phase has been 

 separated in this paper for purposes of discussion. 



FATE OF OIL IN WATER 



When an oil slick occurs, various processes modify and disperse it. 

 The extent and direction of the slick are affected by winds, waves, and currents. 

 The lighter fractions of the oil begin to evaporate within a short time. 

 The heavier fractions are affected by factors such as emulsif ication, disso- 

 lution, photo-oxidation, biodegradation, uptake by marine life, and adsorption 

 to suspended particles. The relative importance of these processes depends 

 on the composition of the oil, especially as it relates to density and vis- 

 cosity, and on external factors such as temperature, light, oxygen, and nutri- 

 ents. Eventually, a tarlike residue is left, which then breaks up into tar 

 lumps or tar balls, which have been observed in waters along tanker routes 

 (Morris 1971, Wong et al . 1974). The following paragraphs contain a discus- 

 sion of the six major factors affecting the heavier fractions of oil in a 

 spill . 



Skidaway Institute of Oceanography 

 P. 0. Box 13687 

 Savannah, Georgia 31406 



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