TABLE 6. Average concentrations of organic extracts (EXT) and 

 hydrocarbons (HC) in sediment cores collected from the Bays of 

 Morlaix and Lannion. 



(*) : excepted surface layer, 



(n) : number of observations, 



(EXT) : IR spectrophotometry determinations of non-purified organic extracts, 



(HC) : IR spectrophotometry determinations of purified organic extracts on florisil. 



ABER WRAC'H (1978 TO 1981) 



The two Abers (Benoit and Wrac'h), located 8 km east of Portsall, 



were heavily impacted during the spill, 

 estuaries, 10-15 km long and about 1 km wide 

 to March 1979 (Marchand and Caprais, 1981) 

 sediments throughout the Abers were heavily 

 were more than 100 ppm and, as in a muddy 

 sometimes reached higher than 10,000 ppm. 

 Caprais (1981) showed that the natural 



These Abers are small 



A study from March 1978 



revealed that the bottom 



polluted. Concentrations 



area in the Aber Benoit, 



After one year, Marchand and 



decontamination process was 



related to the nature of the sediment and the energy level of the 

 geographic zone. The fine- and medium-grained sands located in the 

 exposed, downstream part of the Aber Benoit were well decontaminated 

 (average hydrocarbon content reduced from 700 to 27 ppm) . On the other 

 hand, in mud-dominated areas, the sediment acted as an oil trap (oil 

 content above 10,000 ppm) and decontamination was not observed. For the 

 Aber Benoit, oil pollution of mud-dominated zones such as Loc Majan will 

 be long term. 



In the Aber Wrac'h, the evolution of oil pollution in the bottom 

 sediments has been followed since March 1978. The location of sampling 

 stations is presented in Figure 7; analyses for hydrocarbon and organic 

 carbon concentrations are presented in Tables 7 and 8, respectively. 

 Organic carbon concentrations ranged from 0.08 to 3.32 percent. 

 Sediments are much more homogeneous than those of the Aber Benoit. 

 Composition, with the exception of station 3 located at the mouth of the 

 Aber, varied from slightly muddy to muddy sands. 



152 



