When petroleum is spilled into water, hydrocarbons immediately begin 

 to undergo changes at a rate determined by the composition of the petroleum 

 and characteristics of the environment, such as temperature, concentration 

 of bacteria and nutrients, and wind and wave action. These changes occur 

 through evaporation, solution, spreading, emulsification, air-sea inter- 

 change, oxidation, biological degradation, uptake, and sedimentation. 



Petroleum spilled offshore forms slicks and tar lumps but these are 

 transient conditions. The fate of most spills in the ocean is a combina- 

 tion of evaporation and decomposition in the atmosphere, plus oxidation 

 to carbon dioxide by chemical or biological means. The remaining materials 

 are dispersed in the water column or incorporated into sediments 

 (Figure 53). The more volatile and soluble compounds, representing 



Figure 53. The fate of oil introduced into the marine environment 

 (Source: Reference 166). 



ROCKS 

 BEACHES 



PHOTOCHEMICAL 

 REACTIONS _ 



7 



EVAPORATION 



CLEAN UP 

 OPERATIO^)S 



BIOCHEMICAL 

 OXIDATION 



RATE? 



BURIAL AS 



GEOCHEVttCAL 



DEPOSIT 



to 



approximately 80 percent of the spill volume, disperse within a few weeks. 

 The heavier fraction of petroleum forms tar lumps which are estimated to 

 have a residence time in the ocean of about a year. Tar stranded on rocky 

 shores may have a much longer lifetime. Oil that becomes incorporated in 

 coastal sands protected from the weathering effects of sun and oxygen may 

 have a residence time measured in years or decades. 



Since it is certain that spills will occur from time to time during 

 the operation of a terminal, a plan for containment and recovery operations 

 must be prepared. Success depends on the size of the spill, availability 



195 



