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  • 51. Vonk, Jorien E.
    et al.
    Tesi, Tommaso
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. ISMAR Institute of Marine Sciences, Italy.
    Bröder, Lisa
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Holmstrand, Henry
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Dudarev, Oleg
    Semiletov, Igor
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Distinguishing between old and modern permafrost sources in the northeast Siberian land-shelf system with compound-specific delta H-2 analysis2017In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 11, no 4, p. 1879-1895Article in journal (Refereed)
    Abstract [en]

    Pleistocene ice complex permafrost deposits contain roughly a quarter of the organic carbon (OC) stored in permafrost (PF) terrain. When permafrost thaws, its OC is remobilized into the (aquatic) environment where it is available for degradation, transport or burial. Aquatic or coastal environments contain sedimentary reservoirs that can serve as archives of past climatic change. As permafrost thaw is increasing throughout the Arctic, these reservoirs are important locations to assess the fate of remobilized permafrost OC. We here present compound-specific deuterium (delta H-2) analysis on leaf waxes as a tool to distinguish between OC released from thawing Pleistocene permafrost (ice complex deposits; ICD) and from thawing Holocene permafrost (from near-surface soils). Bulk geochemistry (%OC; delta C-13; % total nitrogen, TN) was analyzed as well as the concentrations and delta H-2 signatures of long-chain n-alkanes (C-21 to C-33) and midto long-chain n-alkanoic acids (C-16 to C-30) extracted from both ICD-PF samples (n = 9) and modern vegetation and Ohorizon (topsoil-PF) samples (n = 9) from across the northeast Siberian Arctic. Results show that these topsoil-PF samples have higher %OC, higher OC/TN values and more depleted delta(COC)-C-13 values than ICD-PF samples, suggesting that these former samples trace a fresher soil and/or vegetation source. Whereas the two investigated sources differ on the bulk geochemical level, they are, however, virtually indistinguishable when using leaf wax concentrations and ratios. However, on the molecular isotope level, leaf wax biomarker delta H-2 values are statistically different between topsoil PF and ICD PF. For example, the mean delta H-2 value of C-29 n-alkane was -246 +/- 13% (mean +/- SD) for topsoil PF and -280 +/- 12 parts per thousand for ICD PF. With a dynamic isotopic range (difference between two sources) of 34 to 50 parts per thousand; the isotopic fingerprints of individual, abundant, biomarker molecules from leaf waxes can thus serve as endmembers to distinguish between these two sources. We tested this molecular delta H-2 tracer along with another source-distinguishing approach, dual-carbon (delta C-13-Delta C-14) isotope composition of bulk OC, for a surface sediment transect in the Laptev Sea. Results show that general offshore patterns along the shelfslope transect are similar, but the source apportionment between the approaches vary, which may highlight the advan-tages of either. This study indicates that the application of delta H-2 leaf wax values has potential to serve as a complementary quantitative measure of the source and differential fate of OC thawed out from different permafrost compartments.

  • 52.
    Wild, Birgit
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bröder, Lisa
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. Vrije Universiteit, Amsterdam, The Netherlands.
    Vonk, Jorien
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    McClelland, James W.
    Song, Wenjun
    Raymond, Peter A.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost2019In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 21, p. 10280-10285Article in journal (Refereed)
    Abstract [en]

    Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO2 and CH4 to directly amplify global warming, another part will enter the fluvial network, potentially providing a window to observe large-scale PP-C remobilization patterns. Here, we employ a decade-long, high-temporal resolution record of C-14 in dissolved and particulate organic carbon (DOC and POC, respectively) to deconvolute PP-C release in the large drainage basins of rivers across Siberia: Ob, Yenisey, Lena, and Kolyma. The C-14-constrained estimate of export specifically from PP-C corresponds to only 17 +/- 8% of total fluvial organic carbon and serves as a benchmark for monitoring changes to fluvial PP-C remobilization in a warming Arctic. Whereas DOC was dominated by recent organic carbon and poorly traced PP-C (12 +/- 8%), POC carried a much stronger signature of PP-C (63 +/- 10%) and represents the best window to detect spatial and temporal dynamics of PP-C release. Distinct seasonal patterns suggest that while DOC primarily stems from gradual leaching of surface soils, POC reflects abrupt collapse of deeper deposits. Higher dissolved PP-C export by Ob and Yenisey aligns with discontinuous permafrost that facilitates leaching, whereas higher particulate PP-C export by Lena and Kolyma likely echoes the thermokarst-induced collapse of Pleistocene deposits. Quantitative C-14-based fingerprinting of fluvial organic carbon thus provides an opportunity to elucidate large-scale dynamics of PP-C remobilization in response to Arctic warming.

  • 53.
    Winiger, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Eckhardt, Sabine
    Stohl, Andreas
    Semiletov, Igor P.
    Dudarev, Oleg V.
    Charkin, Alexander
    Shakhova, Natalia
    Klimont, Zbigniew
    Heyes, Chris
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Siberian Arctic black carbon sources constrained by model and observation2017In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 114, no 7, p. E1054-E1061Article in journal (Refereed)
    Abstract [en]

    Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ng u m-3 to 302 ng.m(-3)) and dual-isotopeconstrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions fromgas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastestwarming regions on Earth.

  • 54.
    Winiger, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Yttri, Karl E.
    Tunved, Peter
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Isotope-Based Source Apportionment of EC Aerosol Particles during Winter High-Pollution Events at the Zeppelin Observatory, Svalbard2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 19, p. 11959-11966Article in journal (Refereed)
    Abstract [en]

    Black carbon (BC) aerosol particles contribute to climate warming of the Arctic, yet both the sources and the source-related effects are currently poorly constrained. Bottom-up emission inventory (El) approaches are challenged for BC in general and the Arctic in particular. For example, estimates from three different El models on the fractional contribution to BC from biomass burning (north of 60 degrees N) vary between 11% and 68%, each acknowledging large uncertainties. Here we present the first dual-carbon isotope-based (Delta C-14 and delta C-13) source apportionment of elemental carbon (EC), the mass-based correspondent to optically defined BC, in the Arctic atmosphere. It targeted 14 high-loading and high-pollution events during January through March of 2009 at the Zeppelin Observatory (79 degrees N; Svalbard, Norway), with these representing one-third of the total sampling period that was yet responsible for three-quarters of the total EC loading. The top-down source-diagnostic C-14 fingerprint constrained that 52 +/- 15% (n = 12) of the EC stemmed from biomass burning. Including also two samples with 95% and 98% biomass contribution yield 57 +/- 21% of EC from biomass burning. Significant variability in the stable carbon isotope signature indicated temporally shifting emissions between different fossil sources, likely including liquid fossil and gas flaring. Improved source constraints of Arctic BC both aids better understanding of effects and guides policy actions to mitigate emissions.

  • 55.
    Winiger, Patrik
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Barrett, T. E.
    Sheesley, R. J.
    Huang, L.
    Sharma, S.
    Barrie, Leonard A.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Yttri, K. E.
    Evangeliou, N.
    Eckhardt, S.
    Stohl, A.
    Klimont, Z.
    Heyes, C.
    Semiletov, I. P.
    Dudarev, O.
    Charkin, A.
    Shakhova, N.
    Holmstrand, Henry
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling2019In: Science Advances, E-ISSN 2375-2548, Vol. 5, no 2, article id eaau8052Article in journal (Refereed)
    Abstract [en]

    Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 +/- 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.

  • 56.
    Wohlfarth, Barbara
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Muschitiello, Francesco
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Steinthorsdottir, Margret
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Watson, Jenny
    Whitehouse, Nicola J.
    Hasseldala-a key site for Last Termination climate events in northern Europe2017In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 46, no 2, p. 143-161Article in journal (Refereed)
    Abstract [en]

    The Last Termination (19 000-11 000 a BP) with its rapid and distinct climate shifts provides a perfect laboratory to study the nature and regional impact of climate variability. The sedimentary succession from the ancient lake at Hasseldala Port in southern Sweden with its distinct Lateglacial/early Holocene stratigraphy (> 14.1-9.5 cal. ka BP) is one of the few chronologically well-constrained, multi- proxy sites in Europe that capture a variety of local and regional climatic and environmental signals. Here we present Hasseldala's multi-proxy records (lithology, geochemistry, pollen, diatoms, chironomids, biomarkers, hydrogen isotopes) in a refined age model and place the observed changes in lake status, catchment vegetation, summer temperatures and hydroclimate in a wider regional context. Reconstructed mean July temperatures increased between c. 14.1 and c. 13.1 cal. ka BP and subsequently declined. This latter cooling coincided with drier hydroclimatic conditions that were probably associated with a freshening of the Nordic Seas and started a few hundred years before the onset of Greenland Stadial 1 (c. 12.9 cal. ka BP). Our proxies suggest a further shift towards colder and drier conditions as late as c. 12.7 cal. ka BP, which was followed by the establishment of a stadial climate regime (c. 12.5-11.8 cal. ka BP). The onset of warmer and wetter conditions preceded the Holocene warming over Greenland by c. 200 years. Hasseldala's proxies thus highlight the complexity of environmental and hydrological responses across abrupt climate transitions in northern Europe.

  • 57. Yan, Caiqing
    et al.
    Zheng, Mei
    Bosch, Carme
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Desyaterik, Yury
    Sullivan, Amy P.
    Collett, Jeffrey L.
    Zhao, Bin
    Wang, Shuxiao
    He, Kebin
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Important fossil source contribution to brown carbon in Beijing during winter2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 43182Article in journal (Refereed)
    Abstract [en]

    Organic aerosol (OA) constitutes a substantial fraction of fine particles and affects both human health and climate. It is becoming clear that OA absorbs light substantially (hence termed Brown Carbon, BrC), adding uncertainties to global aerosol radiative forcing estimations. The few current radiative-transfer and chemical-transport models that include BrC primarily consider sources from biogenic and biomass combustion. However, radiocarbon fingerprinting here clearly indicates that light-absorbing organic carbon in winter Beijing, the capital of China, is mainly due to fossil sources, which contribute the largest part to organic carbon (OC, 67 +/- 3%) and its sub-constituents (water-soluble OC, WSOC: 54 +/- 4%, and water-insoluble OC, WIOC: 73 +/- 3%). The dual-isotope (Delta C-14/delta C-13) signatures, organic molecular tracers and Beijing-tailored emission inventory identify that this fossil source is primarily from coal combustion activities in winter, especially from the residential sector. Source testing on Chinese residential coal combustion provides direct evidence that intensive coal combustion could contribute to increased light-absorptivity of ambient BrC in Beijing winter. Coal combustion is an important source to BrC in regions such as northern China, especially during the winter season. Future modeling of OA radiative forcing should consider the importance of both biomass and fossil sources.

  • 58. Yan, Caiqing
    et al.
    Zheng, Mei
    Sullivan, Amy P.
    Bosch, Carme
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Desyaterik, Yury
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Li, Xiaoying
    Guo, Xiaoshuang
    Zhou, Tian
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Collett, Jeffrey L.
    Chemical characteristics and light-absorbing property of water-soluble organic carbon in Beijing: Biomass burning contributions2015In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 121, p. 4-12Article in journal (Refereed)
    Abstract [en]

    Emissions from biomass burning contribute significantly to water-soluble organic carbon (WSOC) and light-absorbing organic carbon (brown carbon). Ambient atmospheric samples were collected at an urban site in Beijing during winter and summer, along with source samples from residential crop straw burning. Carbonaceous aerosol species, including organic carbon (OC), elemental carbon (EC), WSOC and multiple saccharides as well as water-soluble potassium (K+) in PM2.5 (fine particulate matter with size less than 2.5 mu m) were measured. Chemical signatures of atmospheric aerosols in Beijing during winter and summer days with significant biomass burning influence were identified. Meanwhile, light absorption by WSOC was measured and quantitatively compared to EC at ground level. The results from this study indicated that levoglucosan exhibited consistently high concentrations (209 +/- 145 ng m(-3)) in winter. Ratios of levoglucosan/mannosan (L/M) and levoglucosan/galacosan (L/G) indicated that residential biofuel use is an important source of biomass burning aerosol in winter in Beijing. Light absorption coefficient per unit ambient WSOC mass calculated at 365 nm is approximately 1.54 +/- 0.16 m(2) g(-1) in winter and 0.73 +/- 0.15 m(2) g(-1) in summer. Biomass burning derived WSOC accounted for 23 +/- 7% and 16 +/- 7% of total WSOC mass, and contributed to 17 +/- 4% and 19 +/- 5% of total WSOC light absorption in winter and summer, respectively. It is noteworthy that, up to 30% of total WSOC light absorption was attributed to biomass burning in significant biomass-burning-impacted summer day. Near-surface light absorption (over the range 300-400 nm) by WSOC was about similar to 40% of that by EC in winter and similar to 25% in summer.

  • 59. Yu, Kuangyou
    et al.
    Xing, Zhenyu
    Huang, Xiaofeng
    Deng, Junjun
    Andersson, August
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Fang, Wenzheng
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Gustafsson, Örjan
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Zhou, Jiabin
    Du, Ke
    Characterizing and sourcing ambient PM2.5 over key emission regions in China III: Carbon isotope based source apportionment of black carbon2018In: Atmospheric Environment, ISSN 1352-2310, E-ISSN 1873-2844, Vol. 177, p. 12-17Article in journal (Refereed)
    Abstract [en]

    Regional haze over China has severe implications for air quality and regional climate. To effectively combat these effects the high uncertainties regarding the emissions from different sources needs to be reduced. In this paper, which is the third in a series on the sources of PM2.5 in pollution hotspot regions of China, we focus on the sources of black carbon aerosols (BC), using carbon isotope signatures. Four-season samples were collected at two key locations: Beijing-Tianjin-Hebei (BTH, part of Northern China plain), and the Pearl River Delta (PAD). We find that that fossil fuel combustion was the predominant source of BC in both BTH and PRD regions, accounting for 75 +/- 5%. However, the contributions of what fossil fuel components were dominating differed significantly between BTH and PRD, and varied dramatically with seasons. Coal combustion is overall the all-important BC source in BTH, accounting for 46 +/- 12% of the BC in BTH, with the maximum value (62%) found in winter. In contrast for the PAD region, liquid fossil fuel combustion (e.g., oil, diesel, and gasoline) is the dominant source of BC, with an annual mean value of 41 +/- 15% and the maximum value of 55% found in winter. Region- and season-specific source apportionments are recommended to both accurately assess the climate impact of carbonaceous aerosol emissions and to effectively mitigate deteriorating air quality caused by carbonaceous aerosols.

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