download 21.6mb - Oil-Spill-Info.com

• residual phosphorus,
• residual ammoniacal nitrogen and the intracellular nitrogen concentration
(Kjeldahl's method); these two analyses served to determine
the quantity of biomass formed.
The residual hydrocarbons were extracted from a second liquid sample.
Asphaltenes were precipitated from the hydrocarbon residue using hot
heptane for one hour, dried and weighed.
The residue obtained after evaporation of the heptane was processed to
separate the three main families of hydrocarbons in crude oil:
saturates, aromatics and resins, by thin layer chromatography (50 mg
samples) or liquid chromatography (samples weighing about 1 g) .
The sum of the weights of the three fractions thus recovered, using
liquid chromatography, compared with the initial rate of the hydrocarbons
deposited on the column, always accounted for a proportion
between 90 and 100 %.
The loss percentage increased when the test samples were taken at
increasingly long culture times, hence with samples that underwent the
longest biodegradation times. These losses are likely to be due
largely to the retention of polar compounds of the resins on the
column, compounds that are formed during oxydation reactions, or possibly
by biochemical co-oxydation, and whose concentration increases
with biodegradation time.
Using the different fractions obtained (saturates, aromatics, resins),
we performed more detailed analyses by gas phase chromatography
(Varian 3700 chromatograph) equipped with "Splitless" injection and
flamme ionization detector), a combination of gas phase chromatography
and mass spectrometry (Varian CH5DF spectrometer), proton NMR that
yielded the fraction of hydrogen belonging to methyl groups in the saturates
family, 13 C NMR, which yields the percentage of aromatic carbon
in comparison with total carbon in the aromatic fraction, and by infrared
spectrometry on the resins.
1. BATCH CULTURES
1.1. Biodegradation of hydrocarbon families and sub-families in ALC
240 + .
We selected a mixed culture of bacteria from samples of muds and slud-
ges collected on places hit by crude oil spills.
The experiment was conducted with ALC 240 in an initial concentration
of 2.65 g.l -1 over a , period of 48 hours.
Of the 2.65 g.l -1 of initial hydrocarbons, 1.08 g.l -1 were consumed,
representing 41 % degradation. It appears clearly that the saturates
fraction is most sensitive to biodegradation, because 67 % of this
fraction were consumed, whereas only 27 % of the aromatics fraction
were degraded. The quantity of hydrocarbons evaporated was negligible.
From the standpoint of reproducibility of results, a previous experiment
yielded the following results: hydrocarbons consumed 44 %, saturates
degraded 63.1 %, aromatics disappeared 48.6 %.
29