Ninth International Conference on Permafrost ... - IARC Research

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Content and Composition of Organic Matter in Quaternary Deposits on the LaptevSea CoastA.L. KholodovGeophysical Institute, University of Alaska Fairbanks, USAInstitute of Physical, Chemical, and Biological Problems of Soil Science, RAS, RussiaL. SchirrmeisterAlfred Wegener Institute for Polar and Marine Research, Potsdam, GermanyH. MeyerAlfred Wegener Institute for Polar and Marine Research, Potsdam, GermanyCh. KnoblauchSoil Science Institute of Hamburg University, GermanyK. FahlAlfred Wegener Institute for Polar and Marine Research, Bremerhaven, GermanyIntroductionBecause of freezing and subsequent preservation ofbiomass after sedimentation, permafrost areas are consideredto be important carbon sinks. Mean TOC contents of frozenQuaternary deposits exposed at the Laptev Sea coast arehigh and vary between 3.2 to 11.9 wt% (Grigoriev et al.2004). The organic matter (OM) is preserved in permafrostin the early diagenetic stage of OM maturation. This stageis characterized by a decreasing N content, depletion ofproducts, which have a biological value (carbohydrates,proteins, etc.) and preservation of biopolymers (Bordenave1993). Deeper thawing caused by climate warming can resultin increased decomposition of organic matter and a releaseof greenhouse gases. This study aims a characterization ofthe organic matter in different types of Quaternary depositsat the Laptev Sea coast.The Study Area and Investigated DepositsPermafrost drilling was carried out on the BykovskyPeninsula (SW of Lena River Delta) and Cape Svyatoy Nos(NE of Yana River mouth) in 2001 and 2003 (Kholodov et al.2006). Various types of Quaternary deposits were analyzedfrom both sampling sites:1. Middle Pleistocene deposits of the KuchchuguySuite composed of well-sorted silty loam with numerous thingrass roots. The ice content is in the range from 30 to 50%.The cryostructure is massive. The genesis of these loess-likedeposits is still under debate.2. Late Pleistocene syncryogenic Ice Complex depositsof silt or silty loam with sand and peat layers, fragmentsof twigs and other plant remains, and peat inclusions arecharacterized by volumetric ice content of up to 80–90%and large wedges (up to 30 m high). The Ice Complexdeposits of the Bykovsky Peninsula can be divided into 2groups: those accumulated due to intensive sedimentationrate and formed under the condition of stable ground surfaceposition. The first group was formed during the MIS-4 andMIS-2 periods. The second group was accumulated duringMIS-3 Interstadial. According to previous investigation(Schirrmeister et al. 2002), several periods existed duringthe MIS-3 time, when rates of sedimentation and freezingdecreased and palaeosol horizons were formed over longperiods during several thousands of years. The Ice Complexsequences are in places covered by Late Holocene deposits.3. Late Pleistocene to Holocene deposits in thermokarstdepressions (alases). The formation of these deposits was aresult of thermokarst processes that took place during theLate Pleistocene to Holocene transition period (13–10 kyrBP). This layer can be subdivided into 2 horizons:a. Taberal deposits, that is, former Ice Complexdeposits which were thawed under thermokarst lakes andrefrozen after lake drainage. Taberal deposits are silty loamswith a volumetric ice content of up to 50%.b. Lacustrine to boggy (alas) deposits were formed inshallow lakes or in bogs. These deposits are characterized bya high peat and ice (up to 60%) content.Materials and MethodsThe described deposits were cored using a rotary drillingdevice. The samples were air dried immediately after drilling.Subsequently the material was milled. For determination ofTOC and isotopic composition, carbonates were removedfrom samples by a 1n solution of HCl at 90°C for 3 hoursand washed with distilled water.The following analyses were done:Water (ice) content and density of soil were determinedusing a weight method. Elemental composition of OM: Totalcarbon (TC), total organic carbon (TOC), and nitrogen (N)were determined using the VARIO II Element analyzer.Isotopic composition (δ 13 C) was determined with a FinniganMAT Delta-S mass spectrometer using a FLASH elementalanalyzer and a CONFLO III gas mixing system for onlinedetermination of the carbon isotopic composition. DissolvedOrganic Carbon (DOC) was extracted from sampleswith a CaCl 2solution (4 mM). Subsequently the sampleswere centrifuged and filtered (0.45 µm) (Zsolnay 2003).Biomarkers, to gain better insights into the geochemicalcomposition of the particulate organic carbon n-alkanes (C15to C37), sterols (sum of 24-Methylcholest-5-en-3ß-ol and133
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tTable 1. Main parameters of organic matter in the investigated deposits.Type of deposits n TC,% * TOC, % * TOC/N * CPI δ 13 C, ‰ *;** DOC (mg gTG) *Kuchchuguy Suite 14 0.66–1.82 /1.140.34–1.24 /0.753.25–9.34/6.965–6 -27.28 to -25.70 /-26.180.13–0.26 /0.20 (n=4)Ice Complex 28 0.35–4.53 /1.910.26–3.89 /1.481.67–11.38 /8.75– -27.48 to -23.78 /-25.340.00–0.95 /0.36 (n=25)Taberal deposits 14 0.59–3.28 /1.640.57–2.65 /1.080.84–14.63 /8.444–6 -27.15 to -24.32 /-25.590.11–0.43./0.27 (n=9)Lacustrine /boggy alas deposits11 1.01–6.92 /2.380.93–6.13/1.998.20–11.90 /9.143–5 -26.90 to -23.74 /-25.330.06–0.61 /0.27 (n=9)*Min–max range/average value, ** vs. PDB standard24-Ethylcholest-5-en-3ß-ol), and fatty acids (carbon length14 to 30), were analyzed by means of gas chromatographyaccording to Fahl & Stein (1999). The carbon-preferenceindex(CPI) was calculated after Bray & Evans (1961).Results and DiscussionThe main characteristics of organic matter (TC, TOC,C/N ratio, δ 13 C, CPI and DOC) in Laptev Sea Quaternarydeposits are summarized in Table 1 for the four types ofdeposits. The mean TC contents are between 1 and 2.5%,most of which (about 60%) is composed of organic carbon.Main differences concerning carbon characteristics betweenthe studied deposit types are lowest TC, TOC, DOC content,C/N ratios and δ 13 C values for the Kuchchuguy, whereas IceComplex, Alas and taberal deposits are similar with regardto their organic composition. The mean δ 13 C is about -25.3to -25.5‰ for these deposits, and very similar ranges let usbelieve that the ratio between lacustrine/boggy and terrestrialC3 plant remained the same and the degree of reworking islow. The Kuchchuguy deposits, however, are with -26.1‰slightly lower in δ 13 C with similar minimum values, butisotopically lighter (more negative) maximum values. Thismost likely accounts for the drier conditions and/or highersedimentation rates during Kuchchuguy deposition, with alower relative amount of aquatic biomass in the spectrum.Isotopic composition and C/N ratio indicate a low level ofOM decomposition in all investigated deposits. Only buriedsoils and deposits of the alas complex (both alas and taberal)have C/N values close to the upper (organic) horizonsof modern tundra soils. The biomarker data implicate nosignificant differences between the investigated deposits.Supply of OM and the grade of its maturity depend onthe condition of accumulation. Deposits formed by intensivesedimentation have less OM supply and lowest level of itstransformation due to fast burial and subsequent freezing. Onthe contrary, formed in condition of a stable ground surface,alas deposits and buried soils are characterized by the higherOM supply and level of its maturity.TC content is up to 7 wt%. Most (up to 6 wt%) of this carbonhas organic origin and insoluble in water compounds.Sediments of the highest accumulation rate (Kuchchuguydeposits) have the lowest carbon content and less time toform aquatic organic matter. Decreasing sedimentation rateslead to the accumulation of higher amounts of organic matterfrom one side and its deeper transformation from another.AcknowledgmentsCurrent research was supported by RFBR (grant #05-05-64062) and INTAS (YS #04-83-2950).ReferencesBordenave, M.L. 1993. Applied Petroleum Geochemistry.Enfield, NH: Editions Technip, 524 pp.Ershov, E.D. 1989. Geocryology of USSR Eastern Siberiaand Far East. Moscow: Nedra, 515 pp (in Russian).Fahl, K. & Stein, R. 1999. Biomarkers as organic-carbonsourceand environmental indicators in the LateQuaternary Arctic Ocean: problems and perspectives.Marine Chemistry 63: 293-309.Grigoriev, M.N., Rachold, V.R., Hubberten, H.-W. &Schirrmeister, L. 2004. Organic Carbon input to theArctic Seas through coastal erosion. In: R. Stein &R.W. Macdonald (eds.), The Organic Carbon Cyclein the Arctic Ocean. Berlin, Heidelberg, & New York:Springer, 363 pp.Schirrmeister, L., Siegert, Ch., Kuznetsova, T., KuzminaS., Andreev, A., Kienast, F., Meyer, H. & Bobrov, A.2002. Paleoenvironmental and paleoclimatic recordsfrom permafrost deposits in the Arctic region ofNorthern Siberia. Quaternary <strong>International</strong> 89: 97-118.Zsolnay, A. 2003. Dissolved organic matter: Artefacts,definitions, and functions. Geoderma 113: 187-209.ConclusionFrozen Quaternary deposits of the Laptev Sea region aresignificant reservoirs of low transformed organic matter. The134
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
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Human Experience of Cryospheric Cha
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HiRISE Observations of Fractured Mo
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A Soil Freeze-Thaw Model Through th
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Mapping and Modeling the Distributi
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First Results of Ground Surface Tem
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Historical Changes in the Seasonall
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Rock Glaciers in the Kåfjord Area,
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Snowpack Evolution on Permafrost, N
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Climate Change in Permafrost Region
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370Huang, B. 339Hugelius, G. 105, 1
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