It should be noted that a sample taken at the same time and same 

 place, but at a depth of 25 cm, shows an advanced stage of degradation, 

 comparable to that observed in samples from the Aber Wrac'h at the 

 same time. 



Compared with these subtidal sediments, oxidation degradation of 

 the trapped crude in beach sands is slight and slow. This is seen in 

 the infra-red spectra of the resins, where the absorption bands of the 

 carbonyls are less marked (Fig. 26) . 



KERDENIEL 18.10.78 



treo:ip*:i 31.1.79 



TREO'IPAN 28.3.79 



KERDENIEL 28.3.79 



t r 



3600 3200 



FIGURE 26. Infra-red spectrometry of the resins, 



CONCLUSION 



The samples studied fall into three categories : 



- subtidal sediments (Aber Wrac'h) ; 



- oil/water emulsions or "chocolate mousse" ; 



- intertidal sediments (beach sands) . 



In the slightly muddy sediments of fine sand in the stations lo- 

 cated in the outer part of the Aber Wrac'h, where the marine character 

 is pronounced, a decrease in global contents of extractable compounds 

 is observed, whereas in those located in the upper part of the Aber, 

 the decontamination process is slow, probably inhibited by the muddy 

 nature of the sediments. 



140 



