25th International Meeting on Organic Geochemistry IMOG 2011

P-040
Evolution of organic matter in lignite-containing sediments
under different environmental conditions. Analytical pyrolysis
(Py-GC/MS) proxy
José A. González-Pérez 1 , Abad Chabbi 2 , Cornelia Rumpel 3 , José Mª de la Rosa 4 ,
Francisco J. González-Vila 1
1 IRNAS-CSIC, Seville, Spain, 2 INRA-UEFE, Lusignan, France, 3 INRA-BIOEMCO, Thivernal-Grignon, France,
4 ITN, Sacavém, Portugal (corresponding author:jag@irnase.csic.es)
Mine soils and sediments in Lusatian open-cast lignite
mining district (Germany) contain a mixture of lignite
and recent organic matter. Organic matter (OM)
characterization and its transformation in mine soils
and sediments is essential to understand ecosystem
functioning in this region. For this study analytical
pyrolysis (Py-GC/MS) was used as a geochemical
proxy to complement previous studies done at a
rehabilitated site for soil development 45 years ago
and directed to monitor the different C sources (lignite
or plant derived) in soils and sediments and its degree
of degradation in contrasting environments (Chabbi et
al., 2006, 2007).
Representative vegetation and organic carbon (OC)
rich soil/sediment fraction (humus fraction separated
by flotation) from lake sediments were sampled at two
depths (0-5 and 5-10 cm) in three plots along a
transect covering: an 1) upland forest soil, 2) partially
submerged sediment at the land–water interface and
3) constantly submerged sediment.
The analysis of plant (lipds, isoprenoids,
methoxyphenols & carbohydrates) and possible lignite
(alkyl-napththalenes, alkyl-benzenes & PAHs)
biomarkers released after pyrolysis (500 ºC) supports
previous findings in the area using different proxies.
The conditions in the submerged sediment favors OM
protection and the accumulation of decomposing plant
material, whereas a more intense OM degradation
process seems to be occurring in the land–water
interface area that is characterized by fluctuating
water levels. In addition, the presence of organic
sulfur compounds (OSC); a well resolved series of
alkyl-thiophenes (6 to 24 C) with marked dominance
of even C number molecules, indicate the possible
occurrence of particular mechanisms of C
preservation in this extreme anoxic S rich
environment i.e. via sulfur ―quenching‖ with plant
derived lipids during early diagenesis (Sinninghe-
Damsté et al. 1989; Sinninghe-Damsté & de Leeuw,
1990) in the submerged sediments of rehabilited
lakes.
References:
Chabbi A., Rumpel C., Kögel-Knabner I. (2007) Org.
Geochem. 38: 835–844;
Chabbi A., Rumpel C., Grootes P.M., Mariotti A. Hüttl
R.F. (2006) Org. Geochem. 37: 740–753
Sinninghe-Damsté J.S.; de Leeuw J.W. (1990) Org.
Geochem. 16: 1077–1101
Sinninghe Damsté J.S., Rijpstra W.I.C., Kock-van
Dalen A.C., de Leeuw J.W., Schenck P.A. (1989)
Geochim. Cosmochim. Acta: 53, 1343–1355.
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