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  • 1.
    Alling, Vanja
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sanchez-Garcia, Laura
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Porcelli, Don
    Pugach, Sveta
    Vonk, Jorien E.
    van Dongen, Bart
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences. Stockholm University, Stockholm Resilience Centre.
    Anderson, Leif G.
    Sokolov, Alexander
    Stockholm University, Stockholm Resilience Centre.
    Andersson, Per
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Stockholm Resilience Centre.
    Semiletov, Igor
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Non-conservative behavior of dissolved organic carbon across the Laptev and East Siberian Seas2010In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 24, p. GB4033-Article in journal (Refereed)
    Abstract [en]

    Climate change is expected to have a strong effect on the Eastern Siberian Arctic Shelf (ESAS) region, which includes 40% of the Arctic shelves and comprises the Laptev and East Siberian seas. The largest organic carbon pool, the dissolved organic carbon (DOC), may change significantly due to changes in both riverine inputs and transformation rates; however, the present DOC inventories and transformation patterns are poorly understood. Using samples from the International Siberian Shelf Study 2008, this study examines for the first time DOC removal in Arctic shelf waters with residence times that range from months to years. Removals of up to 10%–20% were found in the Lena River estuary, consistent with earlier studies in this area, where surface waters were shown to have a residence time of approximately 2 months. In contrast, the DOC concentrations showed a strong nonconservative pattern in areas with freshwater residence times of several years. The average losses of DOC were estimated to be 30%–50% during mixing along the shelf, corresponding to a first-order removal rate constant of 0.3 yr−1. These data provide the first observational evidence for losses of DOC in the Arctic shelf seas, and the calculated DOC deficit reflects DOC losses that are higher than recent model estimates for the region. Overall, a large proportion of riverine DOC is removed from the surface waters across the Arctic shelves. Such significant losses must be included in models of the carbon cycle for the Arctic Ocean, especially since the breakdown of terrestrial DOC to CO2 in Arctic shelf seas may constitute a positive feedback mechanism for Arctic climate warming. These data also provide a baseline for considering the effects of future changes in carbon fluxes, as the vast northern carbon-rich permafrost areas draining into the Arctic are affected by global warming.

  • 2. 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.

  • 3.
    Sanchez-Garcia, L
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    de Andrés, J.R.
    Martín-Rubí, J.A.
    Gónzalez-Vila, F.J.
    Polvillo, O.
    Use of lipid biomarker patterns as proxies of environmental variability in coastal sedimentary record from the Gulf of Cádiz (SW Spain).2008In: Org. Geochem., Vol. 39, p. 958-964Article in journal (Refereed)
  • 4.
    Sanchez-Garcia, Laura
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alling, Vanja
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pugach, Svetlana
    Vonk, Jorien
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    van Dongen, Bart
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Dudarev, Oleg
    Semiletov, Igor
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Inventories and behavior of particulate organic carbon in the Laptev and East Siberian seas2011In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 25, p. GB2007-Article in journal (Refereed)
    Abstract [en]

    Fluvial and erosional release processes in permafrost-dominated Eurasian Arctic cause transport of large amounts of particulate organic carbon (POC) to coastal waters. The marine fate of this terrestrial POC (terr-POC), water column degradation, burial in shelf sediments, or export to depth, impacts the potential for climate-carbon feedback. As part of the International Siberian Shelf Study (ISSS-08; August-September 2008), the POC distribution, inventory, and fate in the water column of the extensive yet poorly studied Eurasian Arctic Shelf seas were investigated. The POC concentration spanned 1-152 mu M, with highest values in the SE Laptev Sea. The POC inventory was constrained for the Laptev (1.32 +/- 0.09 Tg) and East Siberian seas (2.85 +/- 0.20 Tg). A hydraulic residence time of 3.5 +/- 2 years for these Siberian shelf seas yielded a combined annual terr-POC removal flux of 3.9 +/- 1.4 Tg yr(-1). Accounting for sediment burial and shelf-break exchange, the terr-POC water column degradation was similar to 2.5 +/- 1.6 Tg yr(-1), corresponding to a first-order terr-POC degradation rate constant of 1.4 +/- 0.9 yr(-1), which is 5-10 times faster than reported for terr-DOC degradation in the Arctic Ocean. This terr-POC degradation flux thus contributes substantially to the dissolved inorganic carbon excess of 10 Tg C observed during ISSS-08 for these waters. This evaluation suggests that extensive decay of terr-POC occurs already in the water column and contributes to outgassing of CO(2). This process should be considered as a geographically dislocated carbon-climate coupling where thawing of vulnerable permafrost carbon on land is eventually adding CO(2) above the ocean.

  • 5.
    Sanchez-Garcia, Laura
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Cato, Ingemar
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Evaluation of the influence of black carbon on the distribution of PAHs in sediments from along the entire Swedish continental shelf2010In: Marine Chemistry, ISSN 0304-4203, E-ISSN 1872-7581, Vol. 119, no 04-jan, p. 44-51Article in journal (Refereed)
    Abstract [en]

    A growing literature proposes that combusted-derived black carbon (BC) dominates the sorption and, by inference, the environmental distribution and bioavailability of many hydrophobic pollutant classes. There is a paucity of studies simultaneously evaluating the distribution of both BC geosorbents and pollutant sorbates in the actual field. Here, 120 surface sediments collected by the Geological Survey of Sweden along the 2000 km continental shelf along the Swedish coast facilitated evaluation of the relative influences of BC and non-BC organic carbon (OC) on the spatial distribution of polycyclic aromatic hydrocarbons (PAHs). The sum of 15 out of the 16 EPA PAHs ranged from 0.12 to 9.6 mu g/g dry weight (dw), with the highest levels being found in the southern half of the Swedish Shelf (SS) area and in the vicinity of larger cities (Stockholm, Goteborg, Malmo and Umea). Source-diagnostic PAH ratios such as ANT/(PHE + ANT), FLT/(FLT + PYR), BaA/(BaA + BPE), IPY/(IPY + BPE), CombPAH/Sigma PAH and LMW/HMW suggested that pyrogenic sources are dominating the load of PAHs in Swedish Baltic and North Sea sediments. The sediment TOC was 4.8-168 mg/gdw (median 43 mg/gdw), while a BC concentration of 0.6-18 mg/gdw (median 1.8 mg/gdw) yielded BC: TOC ratios spanning a wide range of 1.7-47% (median 4.6%). Empirical distribution function tests indicated that the use of linear regression statistics was inappropriate. Instead, evaluation with the non-parametric Spearman function yielded higher correlation coefficient (r(S)) for total PAHs versus BC (0.54, p<0.01) than versus either TOC (0.28, p<0.01) or OC (TOC-BC; 0.26, p<0.01). The results from this field study, encompassing an order of magnitude more observations than any previous sediment study, constitute a broad field manifestation of the importance of BC in affecting the distribution of planar aromatic pollutants in aquatic environments.

  • 6.
    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.

  • 7.
    Vonk, J. E.
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sanchez-Garcia, Laura
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    van Dongen, B. E.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Alling, V.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kosmach, D.
    Charkin, A.
    Semiletov, I. P.
    Dudarev, O. V.
    Shakhova, N.
    Roos, P.
    Eglinton, T. I.
    Andersson, A.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, O.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 489, no 7414, p. 137-140Article in journal (Refereed)
    Abstract [en]

    The future trajectory of greenhouse gas concentrations depends on interactions between climate and the biogeosphere(1,2). Thawing of Arctic permafrost could release significant amounts of carbon into the atmosphere in this century(3). Ancient Ice Complex deposits outcropping along the similar to 7,000-kilometre-long coastline of the East Siberian Arctic Shelf (ESAS)(4,5), and associated shallow subsea permafrost(6,7), are two large pools of permafrost carbon(8), yet their vulnerabilities towards thawing and decomposition are largely unknown(9-11). Recent Arctic warming is stronger than has been predicted by several degrees, and is particularly pronounced over the coastal ESAS region(12,13). There is thus a pressing need to improve our understanding of the links between permafrost carbon and climate in this relatively inaccessible region. Here we show that extensive release of carbon from these Ice Complex deposits dominates (57 +/- 2 per cent) the sedimentary carbon budget of the ESAS, the world's largest continental shelf, overwhelming the marine and topsoil terrestrial components. Inverse modelling of the dual-carbon isotope composition of organic carbon accumulating in ESAS surface sediments, using Monte Carlo simulations to account for uncertainties, suggests that 44 +/- 10 teragrams of old carbon is activated annually from Ice Complex permafrost, an order of magnitude more than has been suggested by previous studies(14). We estimate that about two-thirds (66 +/- 16 per cent) of this old carbon escapes to the atmosphere as carbon dioxide, with the remainder being re-buried in shelf sediments. Thermal collapse and erosion of these carbon-rich Pleistocene coastline and seafloor deposits may accelerate with Arctic amplification of climate warming(2,13).

  • 8.
    Vonk, Jorien E.
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sanchez-Garcia, Laura
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Semiletov, I.
    Dudarev, O.
    Eglinton, T.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Molecular and radiocarbon constraints on sources and degradation of terrestrial organic carbon along the Kolyma paleoriver transect, East Siberian Sea2010In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, no 10, p. 3153-3166Article in journal (Refereed)
    Abstract [en]

    Climate warming in northeastern Siberia may induce thaw-mobilization of the organic carbon (OC) now held in permafrost. This study investigated the composition of terrestrial OC exported to Arctic coastal waters to both obtain a natural integration of terrestrial permafrost OC release and to further understand the fate of released carbon in the extensive Siberian Shelf Seas. Application of a variety of elemental, molecular and isotopic (delta C-13 and Delta C-14) analyses of both surface water suspended particulate matter and underlying surface sediments along a 500 km transect from Kolyma River mouth to the mid-shelf of the East Siberian Sea yielded information on the sources, degradation status and transport processes of thaw-mobilized soil OC. A three end-member dual-carbon-isotopic mixing model was applied to deduce the relative contributions from riverine, coastal erosion and marine sources. The mixing model was solved numerically using Monte Carlo simulations to obtain a fair representation of the uncertainties of both end-member composition and the end results. Riverine OC contributions to sediment OC decrease with increasing distance offshore (35 +/- 15 to 13 +/- 9%), whereas coastal erosion OC exhibits a constantly high contribution (51 +/- 11 to 60 +/- 12%) and marine OC increases offshore (9 +/- 7 to 36 +/- 10%). We attribute the remarkably strong imprint of OC from coastal erosion, extending up to similar to 500 km from the coast, to efficient offshoreward transport in these shallow waters presumably through both the benthic boundary layer and ice-rafting. There are also indications of simultaneous selective preservation of erosion OC compared to riverine OC. Molecular degradation proxies and radiocarbon contents indicated a degraded but young (Delta C-14 ca. -60% or ca. 500 C-14 years) terrestrial OC pool in surface water particulate matter, underlain by a less degraded but old (Delta C-14 ca. -500% or ca. 5500 C-14 years) terrestrial OC pool in bottom sediments. We suggest that the terrestrial OC fraction in surface water particulate matter is mainly derived from surface soil and recent vegetation fluvially released as buoyant organic-rich aggregates (e. g., humics), which are subjected to extensive processing during coastal transport. In contrast, terrestrial OC in the underlying sediments is postulated to originate predominantly from erosion of mineral-rich Pleistocene coasts (i.e., yedoma) and inland mineral soils. Sorptive association of this organic matter with mineral particles protects the OC from remineralization and also promotes rapid settling (ballasting) of the OC. Our findings corroborate recent studies by indicating that different Arctic surface soil OC pools exhibit distinguishing susceptibilities to degradation in coastal waters. Consequently, the general postulation of a positive feedback to global warming from degradation of permafrost carbon may be both attenuated (by reburial of one portion) and geographically displaced (degradation of released terrestrial permafrost OC far out over the Arctic shelf seas).

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