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marker compounds, the C3 dibenzothiophenes, and C3 and C4 phenanthrenes,
persist but the pyrogenic PAH compounds have replaced any AMOCO CADIZ
oil traces at Station 5 in L'Aber Wrac'h.
The last sampling, June 1981, reveals total disappearance of
traces of AMOCO CADIZ aromatic marker compounds at stations 3, 5, and
7. By June 1981 the only unequivocal presence of AMOCO oil is seen at
station 3 in lie Grande, although it has been extremely weathered.
Only pentacyclic triterpanes can be linked to the residual AMOCO oil.
GC patterns suggest that petroleum still affects stations 4, 6, 7, and
8, but in only minor quantities relative to other inputs.
Thus, for the most part, less than three and one half years has
been required to allow normal background inputs to resume their sedimentary
dominance at all but the most heavily impacted (in terms of
post cleanup oil concentrations) and lowest energy (i.e. most protected
from waves) environments (i.e. station 3 in the lie Grande).
Further interpretive details are presented in Atlas et al. (1981).
3.3 Offshore Sediments (Marchand, CNEXO)
L'Aber Benoit Sediments (Courtot, U. West Brittany)
In this phase of the analytical chemical program the levels, the
persistence, and the precise chemical nature of petroleum hydrocarbons
in the offshore sediments of the Bays of Morlaix and Lannion were
examined as well as those of L'Aber Benoit sediments (November 1978
only) . A summary of the samples analyzed appears in Table 7 and in
Fiqure 3.35.
TABLE 7. AMOCO CADIZ chemistry program; 2. Offshore
surface sediments (Marchand) and Aber Benoit
sediments (Courtot) .
Frequency:
April 1978 6
July 1978 14
November 1978 13+7
February 1979 13
TOTAL 53
Locations :
Aber Benoit (November 1978)
Baie de Morlaix
Baie de Lannion
GC/MS :
Four Time Series (18 Samples)
62