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Lipid biomarkers and other geochemical indicators in paleoenvironmental studies of two Arctic systems: a Russian permafrost peatland and marine sediments from the Lomonosov Ridge
Stockholm University, Faculty of Science, Department of Geological Sciences.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The reconstruction of past environmental conditions is a fascinating research area that attracts the interest of many individuals in various geological disciplines. Paleoenvironmental reconstruction studies can shed light on the understanding of past climates and are a key to the prediction of future climate changes and their consequences. These studies take on special significance when focused on areas sensitive to climate change. The Arctic region, which is experiencing dramatic changes today in its peatlands and in its ocean, is prime example. The entire region plays a major role in global climate changes and has recently received considerable interest because of the potential feedbacks to climate change and its importance in the global carbon cycle.

For a better understanding of the role of Arctic peatlands and the Arctic Ocean to global climate changes, more records of past conditions and changes in the region are needed. This work applies different geochemical proxies, with special emphasis on lipid biomarkers, to the study of a permafrost peat deposit collected from the Eastern European Russian Arctic and a marine core retrieved from the Lomonosov Ridge in the central Arctic Ocean. The results reported of this study show that molecular stratigraphy obtained from the analysis of lipid biomarkers in both peat and marine profiles, combined with other environmental proxies, can contribute significantly to the study of Arctic ecosystems of the past.

Place, publisher, year, edition, pages
Stockholm: Department of Geological Sciences, Stockholm University , 2012. , 17 p.
Series
Meddelanden från Stockholms universitets institution för geologiska vetenskaper, 347
Keyword [en]
lipid biomarkers, peat, permafrost, Arctic Ocean, marine sediments
National Category
Earth and Related Environmental Sciences
Research subject
Geochemistry
Identifiers
URN: urn:nbn:se:su:diva-65350ISBN: 978-91-7447-382-7 (print)OAI: oai:DiVA.org:su-65350DiVA: diva2:462647
Public defence
2012-01-23, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2012-01-02 Created: 2011-12-07 Last updated: 2014-09-12Bibliographically approved
List of papers
1. Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic
Open this publication in new window or tab >>Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic
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2011 (English)In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 42, no 9, 1065-1075 p.Article in journal (Refereed) Published
Abstract [en]

Coupled analyses of n-alkane biomarkers and plant macrofossils from a peat plateau deposit in the northeast European Russian Arctic were carried out to assess the effects of past hydrology on the molecular contributions of plants to the peat. The n-alkane biomarkers accumulated over 9.6 kyr of local paleohydrological changes in this complex peat profile in which a succession of vegetation changes occurred during a transition from a wet fen to a relatively dry peat plateau bog. This study shows that the contribution of the n-C31 alkane from rootlets to peat layers rich in fine and dark roots is important. The results further indicate that the n-alkanePaqandn-C23/n-C29 biomarker proxies that have been useful to reconstruct past water table levels in many peat deposits can be misleading when the contributions of Betulaand Sphagnum fuscum to the peat are large. Under these conditions, the C23/(C27+ C31) n-alkane ratio seems to correct for the presence of BetulaandS. fuscum and provides a better description for the relative amounts of moisture. The average chain length (ACL) n-alkane proxy also appears to be a good paleohydrology proxy in having larger values during dry and cold conditions in this Arctic bog setting.

Place, publisher, year, edition, pages
Elsevier, 2011
Keyword
peat, permafrost, n-alkanes, biomarkers, Holocene
National Category
Natural Sciences
Research subject
Biogeochemistry
Identifiers
urn:nbn:se:su:diva-62806 (URN)10.1016/j.orggeochem.2011.06.020 (DOI)000295610800007 ()
Available from: 2011-12-06 Created: 2011-09-30 Last updated: 2017-12-08Bibliographically approved
2. Elemental and isotopic carbon and itrogen records of organic matter accumulation in a Holocene permafrots peat sequence in the East European Russian Arctic
Open this publication in new window or tab >>Elemental and isotopic carbon and itrogen records of organic matter accumulation in a Holocene permafrots peat sequence in the East European Russian Arctic
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

A peat deposit from the East European Russian Arctic, spanning nearly 10,000 years, was investigated to reconstruct past environmental conditions and to study soil organic matter (SOM) degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (~2,500 cal a BP). Total organic carbon (TOC) and total nitrogen (N) concentrations are different in the bog peat compared to the fen peat, with lower values in the moss-dominated bog peat layers.  Lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues.  The atomic ratios of bulk elemental parameters indicate better preservation of organic matter in peat deposits dominated by bryophytes relative to vascular plants.  The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to be associated with better preservation of organic plant material.  δ15N values suggest N isotopic fractionation was driven primarily by microbial decomposition while differences in δ13C values appear to be associated mainly with changes in plant assemblages rather than diagenesis.  Positive shifts in both δ15N and δ13C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface.  This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed 15N-enrichment.

Keyword
Arctic peatlands, permafrost, stable isotopes, elemental anaöyses, macrofossil analyses
National Category
Natural Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-64489 (URN)
Available from: 2011-12-06 Created: 2011-11-18 Last updated: 2012-01-02Bibliographically approved
3. Effect of climate change on delivery and degradation of lipid biomarkers in a Holocene peat sequence in the Eastern European Russian Arctic
Open this publication in new window or tab >>Effect of climate change on delivery and degradation of lipid biomarkers in a Holocene peat sequence in the Eastern European Russian Arctic
2012 (English)In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 53, 63-72 p.Article in journal (Refereed) Published
Abstract [en]

Lipid biomarkers from a peat plateau profile from the Northeast European Russian Arctic were analyzed. The peat originated as a wet fen ca. 9 ka BP and developed into a peat bog after the onset of permafrost ca. 2.5 ka BP. The distributions and abundances of n-alkanols, n-alkanoic acids, n-alkanes, n-alkan-2-ones and sterols were determined to study the effect of degradation on their paleoclimate proxy information. Plant macrofossil analysis was also used in combination with the lipid distributions. The n-alkanol and n-alkanoic acid distributions in the upper part of the sequence generally correspond to compositions expected from plant macrofossil assemblages. Their carbon preference index (CPI) values increase with depth and age, whereas those of the n-alkanes decrease. The different CPI patterns suggest that n-alkanoic acids and n-alkanols deeper in the sequence may be produced during humification through alteration of other lipids. Excursions in the n-alkanoic acid content also suggest an important contribution of invasive roots to the lipid biomarker composition. The CPIs associated with these compounds show that under permafrost conditions organic material from Sphagnum is better preserved than material from vascular plants. Increasing stanol/stenol ratio values and decreasing n-alkane CPI values indicate progressive degradation of organicmatter (OM) with depth. The n-alkan-2-one/n-alkane and n-alkan-2-one/n-alkanoic acid ratioswere shown to be useful proxies that can reflect the degree of OM preservation and suggest that both microbial oxidation of n-alkanes and decarboxylation of n-alkanoic acids produce n-alkan-2-ones in this peat sequence.

National Category
Geochemistry Geophysics
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-87118 (URN)10.1016/j.orggeochem.2012.05.002 (DOI)000312605100011 ()
Note

AuthorCount:2;

Available from: 2013-01-29 Created: 2013-01-28 Last updated: 2017-12-06Bibliographically approved
4. Organic matter delivery to Quaternary sediments of Amundsen Basin, central Arctic Ocean
Open this publication in new window or tab >>Organic matter delivery to Quaternary sediments of Amundsen Basin, central Arctic Ocean
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Quaternary marine sediments retrieved from the central Arctic Ocean in a 30 cm long core, were analyzed for paleoenvironmental reconstruction. n-Alkane biomarkers combined with elemental analyses that include X-ray fluorescence (XRF) core scanning provide complementary information that suggest important influxes of terrigenous derived organic matter (OM) with depth. Changes in the variability of n-alkane-derived and elemental ratios with depth reflect the complexity of the organic carbon cycle in this region. The distributions and abundances of the long-chain n-alkanes reveal a high content of terrigenous derived components and suggest together with mathematical estimations high deliveries of the terrigenous OM in the past. XRF trace metal analyses suggest less-oxygenated bottom waters that may have allowed for better preservation conditions of OM deeper in the core.

Keyword
n-alkanes, biomarkers, Arctic Ocean, Lomonosov Ridge
National Category
Natural Sciences
Research subject
Geochemistry
Identifiers
urn:nbn:se:su:diva-65274 (URN)
Available from: 2011-12-06 Created: 2011-12-06 Last updated: 2012-01-02Bibliographically approved

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