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STATION 6
i—r
3400 3000
1600
31-03-78
FIGURE 14. Infra-red spectrometry of the resins.
by Tissot et al ; they were calculated for the earliest samples only
2(C29 + C31)
R 29-31 = C28 + 2C30 + C32
The relationship shows that in this case, the n-C29 and n-C31
predominate. Where the value is over 1, the odd-numbered carbons predominate.
In Table 2, a compilation of these values for all the
stations, it is seen that R is much higher than 1 at Stations 6 and 8.
Even in March 1978, this presence of natural compounds modified
the distribution of hydrocarbons by family :
- saturated hydrocarbon contents were low ,-
- polar-compound contents (resins and asphaltenes) high.
While the ratio of SAT/ARO decreased slightly, as at Stations 5
and 6 (Fig. 17), degradation of n-alkanes and isoprenoids (pristane
and phytane) was observed throughout the period, showing clearly which
polycyclic alkanes are most resistant to degradation.
The chroma tograms of the aromatic hydrocarbons have very marked
profiles under photometric detection (FPD) , and a persistence in the
unresolved complex mixture (FID) (Fig. 16). Comparison of the results
of the GPC with those of the high resolution MS undertaken on the reference
samples of March 23, 1981 at Portsall, and the sampling taken
126