TABLE 2. Preliminary Results of Total Hydrocarbon Levels in Brittany 

 Sediments (AC=AMOCO CADIZ Oil Indicated by GC-MS Data) 



Evidence for Weathering of Sediment Hydrocarbons 



It was evident that oil was present at depths where extremely re- 

 ducing conditions indicated the lack of oxygen (Aber Wrac'h and the He 

 Grande oiled site), as well as in surface sediments which were more 

 likely exposed to oxygen. This provided an opportunity to compare 

 weathering patterns in sediments with markedly different exposure to 

 oxygen. Since the actual amount of oil could vary between sites, evi- 

 dence of weathering was sought by comparing the relative amounts of 

 hydrocarbons extracted from single samples known to be polluted with 

 AMOCO CADIZ oil. Because of the rapid and extensive biodegradation 

 which apparently followed the AMOCO CADIZ spill (Atlas, et al, 1981; 

 Ward et al, 1980) the comparison of n-alkanes to the more recalcitrant 

 isoprenoid alkanes of similar volatility was not possible as an index 

 of biodegradation. By the first sampling date (December 1978), n-C17/ 



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