Lipids and clays interactions in a productive marine
water column (Antofagasta Bay, Chile)
Adoum Mahamat-Ahmat, Mohammed Boussafir, Claude Le Milbeau, Régis
Guégan, Lydie Le Forestier
To cite this version:
Adoum Mahamat-Ahmat, Mohammed Boussafir, Claude Le Milbeau, Régis Guégan, Lydie Le
Forestier. Lipids and clays interactions in a productive marine water column (Antofagasta
Bay, Chile). 26th International Meeting on Organic Geochemistry, Sep 2013, Tenerife, Spain.
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P - 470
UNIVERSITE D'ORLEANS
Lipids and clays interactions in a productive marine water column (Antofagasta Bay, Chile)
Adoum MAHAMAT AHMAT,
Mohammed BOUSSAFIR, Claude LE MILBEAU, Régis GUEGAN and Lydie LE FORESTIER
,
Université d’Orléans, Institut des Sciences de la Terre d’Orléans (ISTO), CNRS/INSU UMR 7327, F45071 Orléans Cedex 2, France.
INTRODUCTION
A better understanding of the preservation of fresh organic matter (OM) in sedimentary environnements could provide important insights on the crude oil genesis.
Although several models were proposed for the OM preservation with sediaments, few research works (Largeau et al.,1986, Damsté et al.,1990, Boussafir and
Lallier-Verges 1997) were undertaken on the interaction between OM and minerals at different intra-columns zones. For this purpose, this study aims at understanding the OM adsorption onto clay mineral particles localized at different oxygenic conditions along a productive water column. This study provides new insignts about
the association of clay minerals with OM of which chemical nature was clearly determined by a set of complementary techniques.
MATERIALS AND METHODS
Our in situ approach have been driven off Antofagasta, Chile (fig.1). The Bay undergoes Humboldt current on the
surface. Upwelling currents sustains an important biomass. Fluorescence peak observed at 20m of depth
reflects the intense proliferation of this biomass.
Natural and synthetic montmorillonites and natural kaolinite samples have been disposed along the oceanic
water column at three depths corresponding to different water oxygenic conditions (oxic, transition and anoxic).
After different times of exposure, the samples have been removed and characterized by different analytical
techniques: pyrolysis-GC-MS (py-GC-MS), Dissolved Organic Carbon Analyser, X-Ray Diffraction (XRD) and
Infrared Spectroscopy (IR).
VARIATIONS OF DISSOLVED ORGANIC
CARBON(DOC)
0
0.5
1
1.5
2
2.5
3
3.5
4
Water samples GC/MS analyses revealed
that fatty acids are the most abundant
lipidic family in solution along the water column. Besides, alkanes and aromatic compounds (benzoic
alkyles, methoxy- benzenes, phenols) have been observed in lower quantities (fig.3).Clay adsorbed
lipids are principally fatty acids. Aromatic compounds have also been adsorbed (fig.4).
C 16
Photic
Zone
Natural montmorillonite has been identified as the most
efficient clay for global lipids adsorption. Its adsorption
capacity is higher than Synthetic montmonrillonite’s,
which is it self superior than kaolinite’s. Synthetic
montmonrillonite‘s relative low efficiency compared to its
natural homologue is likely induced by its high cristallinity
state and its lack of ionic impurities.
Saturated FAMEs
Unaturated FAMEs
Alkanes
Benzoic Alkyls
Relative
DOC (mg/l)
MARINE WATER INTERACTIONAL LIPIDS AND CLAYS EFFICIENCY
4.5
Abundance
DOC concentrations in water volumes in contact with our
clayey samples have been investigated. During first days
of immersion, analyses revealed an increase of DOC
concentrations near clay samples.Drouin (2007) have
observed similar results in lacustrine area. This attracting
effect drops following clays residence time (fig.2). In fact,
clays proximal DOC concentrations tend to balance with
marine column DOC concentrations after seven days.
C 18
C 14
C 15
C 16:1
Photic zone
C 17
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Time (min)
Transitional
zone
Transition zone
C 16
Relative
Abundance
Anoxic zone
Figure1: Study site location
C 14
C 18
C 15:1
C 15
C 17
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
Tim e (m in)
SWy-Na-2 (2 days)
SWy-Na-2 (7 days)
Despite of a greater availability and a higher diversity
in the photic zone, analyses revealed that lipidic groups
are preferentially adsorbed in the anoxic zone, near to
the water/sediments interface.
62 63 64 65
C 16
Figure 2: DOC concentrations in Natural Wyoming montmorillonites traps
Anoxic
Zone
A
Kaolinite PH
Relative
Besides lipidic groups observed through GC/MS analyses,
immersed clays have adsorbed other molecular families.
IR spectra have revealed N-H, N-O vibrations (fig.5A),
suggesting that amino-acids and other nitrogenous
compounds have interacted.
A
XRD analyses on both montmo-
Abundance
MOLECULAR DIVERSITY AND CLAYS INTERLEAFS
BEHAVIOR
PHENOLS
4%
C 18
C 14
C 15
C 15:1
B
Others
12%
OH
BENZENES
Alkyls
15%
C 17
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52 53
54
55
56
57
58
59
60
61
62
63
64
POLYCYCLICS
ALKANES
BENZENES- 19%
METHOXYBENZENES
Time (min)
Figure 3: Total ionic currents obtained for immersed natural Wyoming
montmorillonite
samples.
Figure 3: Total ionic
currents obtained for immersed natural Wyoming
OH
CH3
O
ALKANES
12%
H3C
O
CH3
montmorillonite samples.
FAMEs
30%
OH
ALKANES
16%
ALCOHOLS
METHOXYBENZENES
65
POLYCYLICS
ALKANES
8%
O
H3C
1%
FAMEs 49%
CH3
37
Ohers
10%
O
H3C
8%
METHOXYBENZE
NES
10%
H3C
CH3
O
ALKYLES
BENZENES
6%
CH3
CH3
O
O
CH3
Kaolinite An
υ C-N
δ N-H
NO2
υ C-O
υ C=O
NO2
Kaolinite Ref
rillonites samples have shown an
increase of (001) plans basal
distances (fig.5B), suggesting
organic molecules intercalation.
(02.11) plans kept the same
angular value, showing that
leafs internal structure have not
been altered during the marine
immersion. Kaolinte interactions
occured entirely on its external
surface.
υ C=O
δ O-H
υ C=O
1000
1100
1200
1300
1400
1500
u (Cm
1600
1700
1800
1900
2000
-1
)
B
2500
Diffracted Intensity (a. u.)
Na SWy-2 Ph dehydrated
Na SWy-2 An dehydrated
Na SWy-2 dehydrated
2000
(001)
(001)
1500
(02.11)
1000
(001)
(02.11)
(002) (002)
500
(02.11)
(002)
Q
Figure 4: Lipidic diversity observed on Natural Wyoming Montmorillonite (A) and
Kaolinite (B) samples immersed in the column anoxic zone.
CONCLUSIONS
-Water column organo-mineral process in Antofagasta bay involves different types of OM. Adsorbed
lipidic fraction is predominated by fatty acids.
-Clay particles maximum adsorption capacity is rapidly reached (2 days of immersion). 2:1 Clay types
are globally more efficient than the selected 1:1 clay type.
-The anoxic zone is the most favorable zone for lipids/clays interactions.
0
2
4
6
8
10
12
14
16
18
20
22
24
2θ (°) λ Cu
Figure 5: FTIR spectra and XRD diffractogramms
of immersed kaolinite
natural wyoming
montmonrillonite samples compared reference
samples. (Ph: Photic; An: Anoxic; Ref: Reference).
REFERENCES
(1) Boussafir M. and Lallier-Vergès E. (1997) Accumulation of organic matter in the kimmeridge Clay formation (KCF): an update fossilisation model for marine petroleum
source-rocks. Marine and Petroleum Geology 14, 75-83.
(2) Largeau C., Casadevall E., Kadouri A. and Metzger P. (1984) Formation of botryococcus-derived kerogens. Comparative study of immature torbanites and of the extant
alga Botryococcus braunii. Organic Geochemistry 6, 327-332.
(3) Sinninghe Damsté J. S., de Leeuw J. W. (1990) Analysis, structure and geochemical significance of organical-bound sulphur in the geosphere: state of the art and future
research. Organic Geochemistry 16, 1077-1101.
(4) Drouin S, 2007.Rôle des argiles dans la préservation et la fossilisation de la Matière Organique pétroligène. Ph.D. thesis, University of Orléans, France, 216pp.