Boiling Point, °C 



600 



100 



(A 



o 



Q. 



3 

 O 



0) 

 tO 



C 



0) 

 O 



QJ 

 Q. 



Crude Oil, Volume Percent. 



Figure 2. Distribution of the chemical compounds of a crude oil. (From John M. Hunt, 

 Petroleum Geochemistry and Geology. W H Freeman and Company, 

 Copyright^ 1979) 



composition of the major boiling range materials found in a typical crude oil (Hunt, 

 1979). Data contained in this figure are useful for predicting the fate or weathering 

 pattern of a petroleum or refined product. Forexample, a spill of gasoline with a low 

 boiling range evaporates in the marine environment. Although different crudes may 

 have compositional curves very different from those in Figure 2, general conclusions 

 as to the potential toxicity of an oil or oil product can be made. For example, mid- 

 boiling aromatics that are regarded as relatively toxic are present in high concentra- 

 tions in kerosene and diesel fuel. Nitrogen, sulfur, and oxygen compounds are also 

 toxic, but those in the high-boiling range (greater than 500°C) may be molecules that 

 are too large to have biological activity. On the other hand, NSO compounds in the 

 diesel fuel range are low in concentration, but they are small, watersoluble, and bio- 

 logically active, and thus are a cause for environmental concern. 



Weathering 



The potential for biological and aesthetic damage by chronic or acute petroleum 

 release is a function of the weathering profile of the oil. When an oil is spilled or dis- 



99 



