25th International Meeting on Organic Geochemistry IMOG 2011

P-251
Long-term, low temperature simulation of early diagenetic
alterations of organic matter from conifers: Terpenoids in the
aromatic hydrocarbon fraction
Shenjun Qin 1,2 , Yuzhuang Sun 1 , Yuegang Tang 2 , Kankun Jin 1
1 Hebei University of Engineering, Handan, China, 2 China University of Mining and Technology, Beijing,
China (corresponding author:qin_s_j@hotmail.com)
Early diagenesis of terrestrial organic matter
from higher plants, in modern sediments, peat, lignite,
etc., is a focus of geological research. With the aim to
investigate early diagenetic alterations of organic
matter from conifers, a long-term (more than five
years) simulation experiment at low temperature
(80°C) has been carried out. The experimental results
about the formation of peat macerals and the
characteristics of aliphatic hydrocarbons have been
reported [1, 2]. In the present study, the coniferous
diagenetic products, mainly terpenoids, in the
aromatic hydrocarbon fraction were analysed.
Leaves, branches and barks from contemporary
Cedrus deodara (Pinaceae) and Platycladus orientalis
(Cupressaceae) were divided into several groups and
mixed with different inorganic materials to keep each
sample in a unique condition. All samples covered by
purified water in closed wide-mouthed bottles were
put into an oven, whose temperature was maintained
at 80°C. In the earlier and later stage of this
simulation experiment, i.e. when it has continued for
approximately one year and five years, a part of each
sample was taken out for the organic geochemical
analyses. GC and GC-MS analyses of the aromatics
from conifers were performed on a Hewlett-Packard
model 6890 GC and that coupled to a Hewlett-
Packard model 5973 quadrupole MSD.
The GC and GC-MS data of selected samples
show that the composition of the aromatic fraction is
more complex than that of the aliphatic one. They
consist of common polycyclic aromatic hydrocarbons
(PAHs), aromatic terpenoids and several unexpected
polar terpenoids (Fig.1). Otto et al. (1997) has also
detected high percentage of similar polar terpenoid
(ferruginol) in the aromatic fraction from conifers [3].
In contemporary samples (P & C) and simulated
samples (Ax-1) in the earlier simulation, no common
PAHs were detected. In the simulated samples (Ax-2)
in the latter simualtion, minor common PAHs were
tested. They may be produced by early diagenesis
but not by biosynthesis [4].
Abundance
100000
80000
60000
40000
20000
Abundance
0
550000
500000
450000
400000
350000
300000
250000
200000
150000
100000
50000
sesquiterpenoids
U1~U3
(MW286)
10 20 30 40 50 60 70 80
Y2
Y1
U1 U2
Y3
Time
0
32.00 34.00 36.00 38.00 40.00 42.00 44.00 46.00
Time-->
TIC
sesquiterpenoids
P
methyl dehydroabietate
dehydroabietate aldehydes
Y1~Y3 (MW 284) A11-1 diterpenoids
Abundance
Abundance
1600000
1400000
1200000
1000000
800000
600000
400000
200000
700000
600000
500000
400000
300000
200000
100000
0
0
sesquiterpenoids
U1~U3(MW286)
10 20 30 40 50 60 70 80
Time
~P+~DPB+diterpenoids
cadalene
TMN P
dehydroabietane
retene
10 20 30 40 50 60 70 80
Fig. 1. GC and GC-MS (TIC) traces of the aromatic fractions
In all coniferous samples, considerable aromatic
and polyunsaturated terpenoids were found. The
variations of their composition and relative abundance
during the simulation show the early diagenetic
pathways of terpenoids from their biogenic precursors.
Furthermore, several natural and evolutionary
polar terpenoids (Ux and Yx), which are seldom
reported in the geosphere, were detected and
identified tentatively. They possibly are isomers of
functionalized abietane-type diterpenoids, which may
give meaningful information about the resources of
coniferous biomarkers and the alternations of
diterpenoids in their early diagenesis.
References
[1] Qin, S. J., Sun, Y. Z., Tang, Y. G. (2010) Geochem. J. 44,
247-259.
[2] Sun, Y. Z., Qin, S. J., Zhao, C. L., Kalkreuth, W (2010) Energ.
Fuel 24, 1124-1128.
[3] Otto, A., Walther, H., Puttmann, W. (1997) Org. Geochem. 26,
105-115.
[4] Meyers, P.A., Ishiwatari, R. (1993) Org. Geochem. 20, 867-
900.
U5
Time
C
A 11 -2
387