/o V 



(Uvivis-s 



m«i«l 01 tOTiui tHiPwTiMS 



ST«! IONS 



FIGURE 10. Distribution of cycloparaf fins by mass spectrometry. 



In the aromatic fraction, chromatographic profiles showed : 



- a loss in light hydrocarbons as from March 31, 1978 ; 



- a positive response in flame photometric detector (FPD) , specific 

 sulfur detector, throughout the period studied, which is significant, 

 given the presence of sulfurous aromatic hydrocarbons (thiophenics) , 

 and indicative of extensive continual pollution (Fig. 11) ; 



- a persistence of dibenzothiophene despite a decrease until June 1980 ; 



- an unresolved complex mixture similar to that of the saturated hydro- 

 carbons. 



Metal (nickel and vanadium) and sulfur contents assessed through 

 various samplings (Table I) confirm the persistence of the pollution, 

 and do not indicate any significant evolution. The divergences observed 

 may be attributed to variations in concentration of the two crudes 

 present in the polluting mixture. It is to be noted that it is not 

 possible to date to establish the cause of a relatively high peak at 

 the level of the n-Cl6 in some saturated hydrocarbon chromatogram. 

 A similar peak appeared at Station 6. 



Station 6 



Decontamination is virtually nil here. In June 1979 A maximum of over 

 6,000 mg of hydrocarbons/kg of sediment was registered ; by June 1980 

 hydrocarbon contents were still over 1,200 mg of hydrocarbons/kg of 

 sediment (Fig. 4) . This is true of all stations where the marine cha- 

 racter of the environment is least pronounced -- that is, in the upper 

 reaches of the Aber. 



As can be generally observed in the stations, the most striking 

 evolution is the degradation of the n-alkanes to n-C30. They appear 

 to evolve very rapidly, since the very first sampling taken at this 

 station on March 31, 1978 indicated that the ratios of pristane/n-C17, 



121 



