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contents determined by mass spectrometry
are on the order of 5 3 %.
Cyclane contents decrease gradually from 14.2 % for the singlemembered
cycloparaf fin rings, to 2.3 % for six-membered rings.
The combination of gas-phase chromatography with mass spectrometry
(GPC/MS) made it possible to distinguish the components of the
aromatic fraction : monoaromatic, diaromatic, and triaromatic hydrocarbons
.
Aromatic sulfur compounds of the thiophenic type are the benzo-
thiophenes, dibenzothiophenes, and naphthobenzothiophenes.
Polar compounds (resins) contain oxygenated functions (principally
hydroxyls and carboxyls) shown by infra-red spectrometer analysis.
Elemental analysis of this resin fraction made it possible to
assess contents of the following elements :
C = 78 %
H = 8.9 %
N = 1.5 %
= 4.5 %
In this case, the oxygen content is not calculated by subtracting
the total of the other contents from 100 %, but is titrated by the
Unterzaucher method.
Asphaltene compounds, separated from the oil by cold-hexane
precipitation, are known to have very complex laminated structures.
Metal (such as nickel and vanadium) and sulfur contents were
determined on a dry extract before deasphalting (Fig. 2). Metals are
essentially present in heavy fractions of crude (resins and asphaltenes)
as chelate compounds. Their contents range from 14 to 16.5 ppm
for nickel and from 45 to 60 ppm for vanadium, with a ratio Ni/V of
0.27 to 0.31. Sulfur contents are on the order of 2.35 % by weight.
These determinations will eventually serve as a point of departure
in following the pathways of the pollutant. It is to be noted
that this study is not intended to cover the light evaporated and/or
dissolved third of the cargo, of which about 25,000 tons is light
aromatic hydrocarbons. Benzene, toluene, and xylene are estimated at
respectively 3,300, 4,600, and 3,000 tons.
EVOLUTION OF THE PHYSICO-CHEMICAL PARAMETERS OF THE HYDROCARBONS
We followed the chemical evolution of the hydrocarbons
different types of samples taken from three areas of pollution :
in three
- subtidal sediments (Aber Wrac'h) ;
- water surface-stable emulsions (hydrocarbons with water, or "choco-
late mousse") ;
- intertidal sediments (beaches) .
The Subtidal Sediments of the Aber Wrac'h
A detailed study of these sediments was made by DUCREUX and
. MARCHAND (1979) (collaboration IFP/COB) The evolution of the
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