The initial evaporative losses of spilled Navy distillate fuels can 

 thus be determined rather closely by a comparison of the gas chromatograms 

 of the original and weathered oils. The losses on more extended weather- 

 ing cannot be determined as accurately. Partly this is due to the fact 

 that there is no discrete demarcation between the ''volatile'' and 

 ''nonvolatile'' portions of the oils. Instead, there is a wide range of 

 volatility of the many components. 



The significance of the gas chromatographic results and the calcu- 

 lations that were made are further discussed in the Appendix. 



A comparison of the gas chromatograms with the thin film evaporation 

 experiments indicates that the weight loss in short term weathering is 

 greater for oils with a greater portion of low boiling components. On 

 the other hand the persistence of thin films is greater for oils with 

 a greater portion of high boiling components. Thus, Oil C evaporated 

 least rapidly in the simulated weathering experiments and in the beginning 

 of the thin film evaporations. However, the same oil evaporated most 

 rapidly at the end of the thin film evaporations; and, in that 

 sense, it was the least persistent of the oils. 



All of the four Navy distillate fuels had distillation temperatures 

 considerably below the specification requirements. Thus, other Navy 

 distillate fuels could be within the specification but because of higher 

 distillation temperatures, they could be appreciably less volatile and 

 more persistent. 



Dissolution and Dispersion 



Fuel oils spilled at sea will also sustain losses due to dissolution 

 and dispersion; but, based on investigations reported in the literature, it 

 is expected that these losses ordinarily would be small and would not 

 appreciably reduce the bulk of the oil. There is a concern, however, 

 that significant amounts of toxic components might be disseminated in 

 the aquatic environment [8]. 



The solubility of hydrocarbons decreases with increasing molecular 

 weight [9]. It is comparatively low for aliphatic hydrocarbons, being less 

 than 1 ppm for normal octane. The solubility increases with increased 

 unsaturation and is considerably higher for aromatic compounds. The 

 solubility is about 50 ppm for isopropylbenzene , but it is lower for the 

 higher molecular weight aromatics present in fuel oils . The aromatic 

 components are not only more soluble than the aliphatic components, 

 but are also more toxic [8]. In one investigation, the seawater 

 extracts of kerosene and of a crude oil contained about 1 ppm aromatics [8]. 

 In another investigation, a maximum of 13 ppm of organic material was 

 extracted from No. 2 fuel oil in a closed static system [10]. 



The dissolution of fuel oil at sea, in a dynamic system, is a 

 complicated problem beyond the scope of the present investigation. 

 A higher organic content of the seawater might be produced by the 

 presence of dispersed material, rather than dissolved material, which 

 may be difficult to distinguish. The small amounts of volatile compounds 

 originally dissolved might be removed comparatively rapidly by aeration. 



10 



