ratio of more than 100 is an index of oil pollution in surface sediments 

 (Table 2). In this study, only four samples had a ratio less than 100; 

 80 percent of collected samples had a ratio more than 200; and 28 

 percent had a ratio more than 1,000. This simple parameter confirmed 

 that the surface sediments were highly contaminated. 



Three sedimentary oil accumulation areas were recognized in the Bay 

 of Morlaix: the Morlaix River, the Penze River, and the east area of 

 the bay around Primel. In the Bay of Lannion, pollution was located 

 beyond a line joining Beg An Fry and the lie Grande marsh (Fig. 5) . On 

 the whole, from July 1978 to February 1979, the decontamination process 

 was related to two essential factors: sediment type and the energy 

 level of the geographic zone. Among muddy and fine-grained sands, a 

 slow decrease in oil content was observed, whereas in areas more exposed 

 to high energy conditions, as around Primel in the eastern part of the 

 Bay of Morlaix, the fine- and coarse-grained sand bottom was rapidly 

 cleaned (Table 3) . 



TABLE 2. Ratio of hydrocarbons/organic carbon (HC/OC) in unpolluted and 

 polluted surface sediments (from Marchand and Roucache, 1981) . 



Bay of Morlaix and Lannion 



45 



9 - 1S47 . 48 - 6065 present study 



I in : 9SU1237 

 i +0 : 



149 



