Change search
Refine search result
1 - 20 of 20
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andersson, Rina A.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meyers, Philip A.
    Effect of climate change on delivery and degradation of lipid biomarkers in a Holocene peat sequence in the Eastern European Russian Arctic2012In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 53, p. 63-72Article in journal (Refereed)
    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.

  • 2.
    Andersson, Rina Argelia
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Meyers, Philip
    Department of Earth and Environmental Sciences, The University of Michigan, Ann Arbor, Michigan, U.S.A..
    Zebür, Yngve
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Crill, Patrick
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mörth, Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Impacts of paleohydrological changes on n-alkane biomarker compositions of a Holocene peat sequence in the eastern European Russian Arctic2011In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 42, no 9, p. 1065-1075Article in journal (Refereed)
    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.

  • 3. Birkholz, Axel
    et al.
    Smittenberg, Rienk H.
    Geological Institute, ETH Zürich, Schweiz.
    Bernasconi, Stefano
    Hajdas, Irka
    Wacker, Lukas
    Isolation and compound specific radiocarbon dating of terrigenous branched glycerol dialkyl glycerol tetraethers (brGDGTs)2013In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 60, p. 9-19Article in journal (Refereed)
  • 4.
    Bröder, Lisa
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Tesi, Tommaso
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. CNR-National Research Council of Italy, ISMAR-Marine Sciences Institute, Italy.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Eglinton, Timothy I.
    Semiletov, Igor P.
    Dudarev, Oleg V.
    Roos, Per
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Historical records of organic matter supply and degradation status in the East Siberian Sea2016In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 91, p. 16-30Article in journal (Refereed)
    Abstract [en]

    Destabilization and degradation of permafrost carbon in the Arctic regions could constitute a positive feedback to climate change. A better understanding of its fate upon discharge to the Arctic shelf is therefore needed. In this study, bulk carbon isotopes as well as terrigenous and marine biomarkers were used to construct two centennial records in the East Siberian Sea. Differences in topsoil and Pleistocene Ice Complex Deposit permafrost concentrations, modeled using delta C-13 and Delta C-14, were larger between inner and outer shelf than the changes over time. Similarly, lignin-derived phenol and cutin acid concentrations differed by a factor of ten between the two stations, but did not change significantly over time, consistent with the dual-carbon isotope model. High molecular weight (HMW) n-alkane and n-alkanoic acid concentrations displayed a smaller difference between the two stations (factor of 3-6). By contrast, the fraction for marine OC drastically decreased during burial with a half-life of 19-27 years. Vegetation and degradation proxies suggested supply of highly degraded gymnosperm wood tissues. Lipid Carbon Preference Index (CPI) values indicated more extensively degraded HMW n-alkanes on the outer shelf with no change over time, whereas n-alkanoic acids appeared to be less degraded toward the core top with no large differences between the stations. Taken together, our results show larger across-shelf changes than down-core trends. Further investigation is required to establish whether the observed spatial differences are due to different sources for the two depositional settings or, alternatively, a consequence of hydrodynamic sorting combined with selective degradation during cross-shelf transport.

  • 5. Choudhary, Preetam
    et al.
    Routh, Joyanto
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Distribution of polycyclic aromatic hydrocarbons in Kumaun Himalayan Lakes, northwest India2010In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 41, no 9, p. 891-894Article in journal (Refereed)
    Abstract [en]

    Sources and historical deposition of polycyclic aromatic hydrocarbons (PAHs) were investigated in dated sediment cores from Lakes Nainital and Bhimtal in the Kumaun Himalaya The data show that PAH deposition has increased in recent years and is associated with an increase in anthropogenic activity. The lake sediments dominantly contain low molecular weight (LMW) PAHs. derived mainly from petrogenic sources Concentrations of individual and total PAHs were categorized on the basis of sediment quality criteria. According to this, the pollutants pose a potential threat to aquatic life.

  • 6. Cooke, M.P.
    et al.
    van Dongen, B.E.
    Talbot, H.M.
    Semiletov, I.
    Shakhova, N.
    Guo, L.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bacteriohopanepolyol biomarker composition of organic matter exported to the Arctic Ocean by seven of the major Arctic rivers2009In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 11, p. 1151-1159Article in journal (Refereed)
    Abstract [en]

    Bacteriohopanepolyols (BHPs) are a diverse group of membrane lipids produced by a wide variety of bacteria and can be used as molecular biomarkers for bacterial processes and populations in both modern and ancient environments. A group of BHPs, including adenosylhopane and structurally related compounds, have been identified as being specific to soils, enabling the transport of terrestrial organic matter (terrOM) to the marine realm to be monitored. Estuary surface sediment samples were obtained from the five Great Russian Arctic Rivers (GRARs: Ob, Yenisey, Lena, Indigirka and Kolyma) and river sediments were obtained from two North American Rivers (Yukon and Mackenzie). Analysis of the BHP signatures, using high performance liquid chromatography-tandem mass spectrometry (HPLC-MSn), indicated the presence of 15 different BHPs originating from a variety of different bacteria, as well as a significant presence of terrestrially derived OM. Total BHP abundance and the contribution of the "soil-marker" BHPs to the total BHP pool increased eastwards among the GRAR sediments. This suggests increasing terrestrial OM or increased preservation of OM as a result of shorter periods of permafrost thawing. The North American rivers showed greatly differing BHP levels between the Yukon and Mackenzie rivers, with a greater BHP input and thus a relatively higher soil OM contribution from the Yukon. The Indigirka River basin in the eastern Siberian Arctic appeared to be the epicentre in the pan-Arctic BHP distribution trend, with the highest "soil-marker" BHPs but the lowest tetrafunctionalised BHPs. Aminobacteriohopanepentol, an indicator of aerobic methane oxidation, was observed in all the sediments, with the source being either the marine environment or methane producing terrestrial environments.

  • 7. Gierga, Merle
    et al.
    Schneider, Maximilian P. W.
    Wiedemeier, Daniel B.
    Lang, Susan Q.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hajdas, Irka
    Bernasconi, Stefano M.
    Schmidt, Michael W. I.
    Purification of fire derived markers for mu g scale isotope analysis (delta C-13, Delta C-14) using high performance liquid chromatography (HPLC)2014In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 70, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Black carbon (BC) is the residue of incomplete biomass combustion. It is ubiquitous in nature and, due to its relative persistence, is an important factor in Earth's slow-cycling carbon pool. This resistant nature makes pure BC one of the most used materials for C-14 dating to elucidate its formation date or residence time in the environment. However, most BC samples cannot be physically separated from their matrices, precluding accurate C-14 values. Here we present a method for radiocarbon dating of the oxidation products of BC, benzene polycarboxylic acids, thereby circumventing interference from extraneous carbon. Individual compounds were isolated using high performance liquid chromatography (HPLC) and converted to CO2 via wet chemical oxidation for C-13 and C-14 isotope analysis. A detailed assessment was performed to identify and quantify sources of extraneous carbon contamination using two process standards with distinct isotopic signatures. The average blank was 1.6 +/- 0.7 mu g C and had an average radiocarbon content of 0.90 +/- 0.50 (FC)-C-14. We successfully analyzed the C-14 content of individual benzene polycarboxylic acids with a sample size as small as 20-30 mu g C after correcting for the presence of the average blank. The combination of delta C-13 and (FC)-C-14 analysis helps interpret the results and enables monitoring of extraneous carbon contribution in a fast and cost efficient way. Such a molecular approach to radiocarbon dating of BC residues enables the expansion of isotopic BC studies to samples that have either been too small or strongly affected by non-fire derived carbon.

  • 8.
    Muschitiello, Francesco
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    The C20 highly branched isoprenoid biomarker – a new diatom-sourced proxy for summer trophic conditions2015In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 81, p. 27-33Article in journal (Refereed)
    Abstract [en]

    The exact biological source of the C20 highly branched isoprenoid (HBI) present in sediments from aquatic systems is unclear. We therefore examined the relationship between the distribution of fossil diatoms and the concentration of the C20 HBI in a Late Glacial sedimentary record from the Hässeldala Port paleolake in southern Sweden. Using Bayesian multiple linear regression analysis, we show that its concentration is linked primarily to the production of the diatom taxon Gomphonema acuminatum, which accounts for the largest proportion of the temporal variability in the biomarker. By analogy with modern observations, we argue that an increasing amount of G. acuminatum biomass in our sedimentary record reflects increasing oligotrophy in the paleolake during the summer growing season, especially at times defined by subdued hydrologic flow. Our conclusions are corroborated by the δ13C composition of the C20 HBI biomarker, which points to a negative photosynthetic fractionation between atmospheric CO2 and the pool of dissolved inorganic carbon during diatom bloom, a distinct phenomenon at times of inhibited hydrological flow. Accordingly, we suggest that the C20 HBI biomarker can be effectively used to reconstruct the trophic state of the paleolake at Hässeldala Port, while its stable isotope composition can provide physicochemical information about the lake conditions during the dry summer season.

    Moreover, we note that the major hydrological shifts recorded in the G. acuminatum-C20 HBI stratigraphy do not coincide with the pollen zone boundaries. We thus infer that aquatic and terrestrial environmental responses to climate change are substantially decoupled through the hydrological system, which highlights the necessity for multi-proxy investigations to decipher past climate events.

  • 9. Naeher, Sebastian
    et al.
    Peterse, Francien
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Niemann, Helge
    Zigaha, P
    Schubert, Carsten
    Sources of glycerol dialkyl glycerol tetraethers (GDGTs) in catchment soils, water column and sediments of Lake Rotsee (Switzerland) – Implications for the application of GDGT-based proxies for lakes.2014In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 6, p. 164-173Article in journal (Refereed)
  • 10. Naeher, Sebastian
    et al.
    Peterse, Francien
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Niemann, Helge
    Zigaha, P
    Schubert, Carsten
    Tracing the methane cycle with lipid biomarkers in Lake Rotsee (Switzerland).2014In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 66, p. 174-181Article in journal (Refereed)
  • 11.
    Naeher, Sebastian
    et al.
    EAWAG. Swiss Federal Institute pf Aquatic Science and Technology.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gilli, Adrian
    Kirilova, Emiliya P.
    Lotter, André F.
    Schubert, Carsten J.
    Impact of recent lake eutrophication on microbial community changes as revealed by high resolution lipid biomarkers in Rotsee (Switzerland)2012In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 49, p. 86-95Article in journal (Refereed)
    Abstract [en]

    The effects of eutrophication on short term changes in the microbial community were investigated using high resolution lipid biomarker and trace metal data for sediments from the eutrophic Lake Rotsee (Switzerland). The lake has been strongly influenced by sewage input since the 1850s and is an ideal site for studying an anthropogenically altered ecosystem. Historical remediation measures have had direct implications for productivity and microbial biota, leading to community composition changes and abundance shifts. The higher sewage and nutrient input resulted in a productivity increase, which led predominantly to a radiation in diatoms, primary producers and methanogens between about 1918 and 1921, but also affected all microorganism groups and macrophytes between about 1958 and 1972. Bacterial biomass increased in 1933, which may have been related to the construction of a mechanical sewage treatment plant. Biomarkers also allowed tracing of fossil organic matter/biodegraded oil contamination in the lake. Stephanodiscus parvus, Cyclotella radiosa and Asterionella formosa were the dominant sources of specific diatom biomarkers. Since the 1850s, the cell density of methanogenic Archaea (Methanosaeta spp.) ranged within ca. 0.5–1.8 × 109 cells g−1 dry sediment and the average lipid content of Rotsee Archaea was ca. 2.2 fg iGDGTs cell−1. An altered BIT index (BITCH), indicating changes in terrestrial organic matter supply to the lake, is proposed

  • 12. Roth, Philipp J.
    et al.
    Lehndorff, Eva
    Brodowski, Sonja
    Bornemann, Ludger
    Sanchez-Garcia, Laura
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Amelung, Wulf
    Differentiation of charcoal, soot and diagenetic carbon in soil: method comparison and perspectives2012In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 46, p. 66-75Article in journal (Refereed)
    Abstract [en]

    The various sources of pyrogenic and coalified carbon (black carbon, BC) in soil have considerable structural heterogeneity, making the quantification of BC a challenge. This study was aimed at evaluating the capability of different detection procedures to recover different types of BC from soil. We added defined quantities of urban dust (UD, NIST SRM1649a), diesel particulate matter (DPM, NIST SRM2975), charcoal, lignite, bituminous coal and wood to four topsoil samples. Mixtures were analyzed by way of chemothermal oxidation (CTO), thermal gradient oxidation (ThG), the benzene polycarboxylic acid method (BPCA) and mid-infrared spectroscopy (MIRS). CTO returned good quantification of soot BC in the pure DPM, yet the recovery of soot BC from soil was unsatisfactory (18-270%). ThG gave good precision but lower values for pure soot BC. It severely overestimated the BC content for all soil-standard mixtures. The BPCA method gave a low return for soot BC, but for the spiked soil it reliably detected charcoal and coalified C (69-107% avg. recovery) but underestimated soot BC (52-90% recovery of DPM). Linear coherence in specific MIR vibrations was found in one component soil-BC mixtures for each BC type. Applying these standard calibrations to multi-component mixtures allowed detecting charcoal and a quantification of soot BC (88% avg. recovery) via MIRS, but ignored the presence of diagenetic C. We see the greatest potential in differentiating soot from charcoal in soil by employing a combination of chemical and thermal oxidation and MIRS, while the differentiation from diagenetic C is not possible yet.

  • 13.
    Rueda, Gemma
    et al.
    Universitat Autònoma de Barcelona.
    Rosell-Melé, Antoni
    Universitat Autònoma de Barcelona.
    Escala, Marina
    Universitat Autònoma de Barcelona.
    Gyllencreutz, Richard
    Universitetet i Bergen.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Comparision of instrumental and GDGT based estimates of sea surface and air temperatures from the Skagerrak2009In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 2, p. 287-291Article in journal (Refereed)
    Abstract [en]

    Sea surface temperatures (SSTs) and annual mean air temperatures (MATs) are estimated for the last 200 years from glycerol dialkyl glycerol tetraethers (GDGTs) proxies in a marine sediment core from the Skagerrak, off southern Norway. The reconstructed values compare well with annual SSTs and summer air temperatures obtained from composite regional instrumental records. The results provide further confidence in the application of proxies based on GDGTs to estimate past temperatures.

  • 14. Selver, Ayca Dogrul
    et al.
    Sparkes, Robert B.
    Bischoff, Juliane
    Talbot, Helen M.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Semiletov, Igor P.
    Dudarev, Oleg V.
    Boult, Stephen
    van Dongen, Bart E.
    Distributions of bacterial and archaeal membrane lipids in surface sediments reflect differences in input and loss of terrestrial organic carbon along a cross-shelf Arctic transect2015In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 83-84, p. 16-26Article in journal (Refereed)
    Abstract [en]

    Enhanced climate warming affecting the Arctic region could have a dramatic impact on the terrigenous organic carbon (terrOC) stored in the Eurasian permafrost and could increase the amount of OC remobilized to the Arctic shelves. An improved understanding of the fate of this remobilized soil OC is essential for better understanding of the consequences for the Arctic and global carbon cycle. In this study, glycerol dialkyl glycerol tetraethers (GDGTs) and bacteriohopanepolyols (BHPs) in surface sediments along a 500 km cross shelf transect from the mouth of the Kolyma River to the middle of the vast East Siberian Sea were analysed to assess their potential and that of the associated branched and isoprenoid tetraether (BIT) and R'(soil) indices for tracing terrOC in Arctic systems. Both BHP and GDGT contributions indicated the greatest contribution of terrOC close to the river mouth, while the associated indices showed declining trends in an offshore direction, supporting an increasing marine OC input and/or a decrease in terrOC. However, while the BHPs indicated a dominance of terrOC at the start of the transect, the GDGTs suggested a much larger, almost 50%, marine OC input at this point. In addition, the BIT index displayed an exponential decline, controlled mainly by a substantial contribution of marine GDGTs, while R'(soil) revealed a linear trend governed primarily by the removal of soil marker BHPs. These field results suggest that both biomarker approaches could be used to trace terrigenous derived OC in the Arctic environment. However, using a single proxy approach is not recommended and may lead to an under or over estimation of the relative importance of terrOC. Using a multi-proxy approach is valuable for fully understanding the fate of terrigenous derived OC along Arctic land-ocean transects.

  • 15. Selver, Ayca Dogrul
    et al.
    Talbot, Helen M.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Boult, Stephen
    van Dongen, Bart E.
    Soil organic matter transport along an sub-Arctic river-sea transect2012In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 51, p. 63-72Article in journal (Refereed)
    Abstract [en]

    Bacteriohopanepolyols (BHPs) and glycerol dialkyl glycerol tetraethers (GDGTs) have potential as soil-tracing biomarkers for the extensive shelves of the Arctic Ocean. In this work these biomarkers were analysed in surface sediments along a well characterised sub-Arctic transect in the northernmost Baltic Sea from the Kalix River to the central Bothnian Bay to assess their environmental behaviour and potential for tracing the contribution of soil in this type of system. There was a high BHP diversity and enhanced total BHP concentration in the estuarine sediments, whereas a much less diverse pattern could be observed in the open bay with lower total BHP concentration. In addition, both soil marker BHPs (adenosylhopanes) and branched GDGTs were substantially more abundant in the estuarine than the open bay sediments. The R'(soil) index, based on the R-soil index minus the contribution from the methylated soil marker BHPs, is suggested as a new approach for tracing soil derived organic matter (OM) in the (sub)-Arctic region. The index decreased along the transect in an off-river direction, correlating strongly with both the branched and isoprenoid tetraether (BIT) index and the stable carbon isotopic composition of the sedimentary organic carbon. These field results indicate that both the R'(soil) and the BIT indices have potential for tracing soil derived OM in sub-Arctic to Arctic waters.

  • 16.
    Siljeström, Sandra
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Hode, Tomas
    Lausmaa, Jukka
    Sjövall, Peter
    Toporski, Jan
    Thiel, Volker
    Detection of organic biomarkers in crude oils using ToF-SIMS2009In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 1, p. 135-143Article in journal (Refereed)
    Abstract [en]

    In this study, we show that time of flight-secondary ion mass spectrometry (ToF-SIMS) can be used todetect organic biomarkers, such as hopanes and steranes, in non-fractionated crude oils, without extractionand chemical preparation. Hopanes and steranes may provide valuable information on the history oflife on early Earth, particularly if they are present in fluid inclusions in ancient rocks. Due to the presenceof different generations of inclusions in even very small rock samples, it would be advantageous to find amethod capable of detecting biomarkers in single oil rich fluid inclusions. The capability of ToF-SIMS fordetailed chemical analysis of very small sample amounts makes it a potential technique for such analysis,and in this work this possibility is explored. The presence of hopanes and steranes in four different crudeoils of different ages and stages of biodegradation was investigated using ToF-SIMS and GC–MS. By combininganalyses of biomarker standards, crude oils and chromatographic oil fractions, specific peaks forthe different biomarkers were identified in the ToF-SIMS spectra. The presence of these peaks in the spectrafrom the crude oil samples could be attributed to the biomarkers based on exact mass determinationand by comparison with the spectra from the biomarker containing and biomarker lacking fractions,respectively. In addition, the results show that a significant biomarker signal may be obtained from a 10 µm2 oil sample, demonstrating the potential of ToF-SIMS for analysis of single oil bearing fluid inclusions,which in turn may contribute to a better understanding of the early history of life on Earth.

  • 17.
    Sánchez-García, Laura
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    de Andres, J.R.
    Martin-Rubi, J.A.
    Louchouarn, P.
    Diagenetic state and source characterization of marine sediments from the inner continental shelf of the Gulf of Cadiz (SW Spain), constrained by terrigenous biomarkers2009In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 2, p. 184-194Article in journal (Other academic)
    Abstract [en]

    Surface sediments from the Gulf of Cadiz (GoC) were analyzed by alkaline CuO oxidation, in order to estimate the contribution of terrigenous organic matter (TOM) to the inner continental shelf of the southwest Iberian Peninsula. The parallel analysis of sediment samples from the two most important rivers draining to this coastal area (i.e. Guadiana River and Tinto-Odiel fluvial system) provided fundamental information regarding local terrestrial sources. Relatively constant intensive lignin parameters (S:V= 1.0 +/- 0.1 and C:V= 0.22 +/- 0.04) and high values of the lignin phenol vegetation index (LPVI = 155 +/- 43) indicated that non-woody angiosperm tissues constitute the dominant component of vascular plant material reaching the shelf sediments. The NW to SE decreasing isotopic (C-13) and molecular (As) signatures found among the sediments, coinciding with the Guadiana delivery plume, suggest that this river is the main terrestrial source in the inner GoC shelf Slightly elevated values of degradation indicative ratios ([Ad:Al](v) = 0.41 +/- 0.10: [Ad:Al])(s)=0.34 +/- 0.07; [3,5-Bd:V]=0.14 +/- 0.05; P:[V + S] = 0.24 +/- 0.09) suggested the alteration state of the shelf sediments. The two fold higher ratios of the river sediments (Guadiana: [Ad:Al](v) = 0.82 +/- 0.08: [Ad:Al](s) = 0.84 +/- 0.03; Tinto-Odiel: [Ad:Al](v) = 0.86 +/- 0.12; [Ad:Al](s) = 0.83 +/- 0.013) and the increasing degradation trend observed outward in the shelf, lead us to consider preferential sorption processes, instead of in situ diagenesis, to affect the degradation signature of the shelf sediments. Preferentially solubilized degraded OM is more likely to be sorbed and stabilized prior to transport to the marine system, showing an apparently more advanced degradation state. The use of the 3,5-Bd:V ratio in conjunction with (Ad:Al)(v) revealed a composition continuum of the sedimentary OM ranging from fresh plant materials to highly altered soil humic constituents. Elemental and molecular analyses show a land to sea gradient by a NW to SE decrease of the terrestrial influence, accounting for larger terrestrial inputs (TOM: 71-98%) in those sediments near the Guadiana mouth, and predominantly autochthonous composition (TOM: 42-50%) in those located offshore. This work utilizes lignin derived biomarkers to determine the contribution of terrigenous OM delivered to this poorly described coastal area from regional rivers. Within a context of increasing international efforts to better understand the global C cycling, this study illustrates the relevance of using the alkaline CuO oxidation approach to evaluate C budgets and continental influence in river dominated ocean margins.

  • 18.
    Vonk, J.E.
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Calibrating n-alkane Sphagnum proxies in sub-Arctic Scandinavia2009In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 40, no 10, p. 1085-1090Article in journal (Refereed)
    Abstract [en]

    Moss covered, high latitude wetlands hold large amounts of terrestrial organic matter (OM), which may be vulnerable to expected climate warming. Molecular analysis of fluvially transported material from these regions can distinguish between different sources of terrestrial OM. Sphagnum moss may represent one of the major sources. This study aimed to quantitatively establish a molecular proxy for identifying Sphagnum-derived OM from high latitude peatlands in the sub-Arctic coastal ocean. We collected and analyzed Sphagnum species throughout northern Sweden and Finland. Results show that the C25/(C25 + C29) n-alkane ratio is most suitable for terrestrial OM source apportionment in these coastal regions since, compared to other n-alkane Sphagnum proxies, it shows (i) the least variation between species, (ii) the most constant values for different latitudinal regimes and (iii) the largest dynamic range to the higher plant end member in two-source mixing models. Application of the proxy to surface sediments and suspended particulate matter in the sub-Arctic northern Baltic Sea shows that 68–103% of the terrestrial OM fraction is derived from Sphagnum-rich peatland. We recommend that future studies on terrestrial OM fluxes into (sub-)Arctic regions should apply the C25/(C25 + C29) proxy to improve insight into the contribution of Sphagnum-derived terrestrial OM from climate-vulnerable, high latitude wetlands.

  • 19. Wilson, Rachel M.
    et al.
    Tfaily, Malak M.
    Rich, Virginia I.
    Keller, Jason K.
    Bridgham, Scott D.
    Medvedeff Zalman, Cassandra
    Meredith, Laura
    Hanson, Paul J.
    Hines, Mark
    Pfeifer-Meister, Laurel
    Saleska, Scott R.
    Crill, Patrick
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Cooper, William T.
    Chanton, Jeff P.
    Kostka, Joel E.
    Hydrogenation of organic matter as a terminal electron sink sustains high CO2: CH4 production ratios during anaerobic decomposition2017In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 112, p. 22-32Article in journal (Refereed)
    Abstract [en]

    Once inorganic electron acceptors are depleted, organic matter in anoxic environments decomposes by hydrolysis, fermentation, and methanogenesis, requiring syntrophic interactions between microorganisms to achieve energetic favorability. In this classic anaerobic food chain, methanogenesis represents the terminal electron accepting (TEA) process, ultimately producing equimolar CO2 and CH4 for each molecule of organic matter degraded. However, CO2:CH4 production in Sphagnum-derived, mineral-poor, cellulosic peat often substantially exceeds this 1:1 ratio, even in the absence of measureable inorganic TEAs. Since the oxidation state of C in both cellulose-derived organic matter and acetate is 0, and CO2 has an oxidation state of +4, if CH4 (oxidation state -4) is not produced in equal ratio, then some other compound(s) must balance CO2 production by receiving 4 electrons. Here we present evidence for ubiquitous hydrogenation of diverse unsaturated compounds that appear to serve as organic TEAs in peat, thereby providing the necessary electron balance to sustain CO2:CH4 > 1. While organic electron acceptors have previously been proposed to drive microbial respiration of organic matter through the reversible reduction of quinone moieties, the hydrogenation mechanism that we propose, by contrast, reduces CAC double bonds in organic matter thereby serving as (1) a terminal electron sink, (2) a mechanism for degrading complex unsaturated organic molecules, (3) a potential mechanism to regenerate electron-accepting quinones, and, in some cases, (4) a means to alleviate the toxicity of unsaturated aromatic acids. This mechanism for CO2 generation without concomitant CH4 production has the potential to regulate the global warming potential of peatlands by elevating CO2:CH4 production ratios.

  • 20.
    Yamoah, Kweku Kyei Afrifa
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chabangborn, Akkaneewut
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chulalongkorn University, Thailand.
    Chawchai, Sakonvan
    Stockholm University, Faculty of Science, Department of Geological Sciences. Chulalongkorn University, Thailand.
    Väliranta, Minna
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Smittenberg, Rienk
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Large variability in n-alkane δ13C values in Lake Pa Kho (Thailand) driven by wetland wetness and aquatic productivity2016In: Organic Geochemistry, ISSN 0146-6380, E-ISSN 1873-5290, Vol. 97, p. 53-60Article in journal (Refereed)
    Abstract [en]

    Understanding past climate and environmental conditions depends largely on accurate interpretations of proxy records from a range of environments, including tropical wetlands and lakes. Lipid biomarker analysis can provide important information about the sources of the accumulated organic material, and thus about the environmental information contained therein. Here we use n-alkane distributions and stable carbon isotopes of leaf waxes (δ13Cwax) to identify the sources of organic matter (OM) of a 2000-year long sediment/peat record from Lake Pa Kho (LPK) in northeastern Thailand, and to constrain the mechanisms that cause shifts in δ13Cwax and in δ13C of bulk organic matter (δ13Cbulk). Our results show three main sources of OM: terrestrial plants, aquatic macrophytes and algae. The δ13C values of the long chain n-alkanes, show two distinct groups: C27–C31 and C33–C35n-alkanes, where the δ13C values of C33–C35n-alkanes reflect that of δ13Cbulk. Lower moisture availability on the wetland, known from other sedimentary evidence, was characterized by low carbon isotope values typically seen for C3 plants, whereas greater moisture availability corresponded to higher δ13C values (around –20‰) of C33–C35n-alkanes, resembling a typical C4 plant signal. However, various lines of evidence argue against large shifts between C3 and C4 plant input. Instead, we suggest that the high δ13C values were indirectly caused by higher aquatic productivity during periods of greater moisture availability, decreasing dissolved CO2, but increasing bicarbonate availability caused by higher pH. This caused the dominant macrophytes (e.g., Potamogeton spp.) to shift their carbon source from CO-2 to bicarbonate, which has much higher δ13C values. Our results show that the environmental context should be taken into account when interpreting n-alkane δ13C variability as a paleo-environmental/climatic signal as this contains several important variables that need to be disentangled and explained.

1 - 20 of 20
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf