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GLOBAL BIOGEOCHEMICAL CYCLES,
VOL. 18,
GB1036,
doi:10.1029/2003GB002087,
2004
Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export
Laodong Guo
International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA
Igor Semiletov
International Arctic Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA Pacific Oceanological Institute, Russian Academy of Science, Vladivostok, Russia
Örjan Gustafsson
Institute of Applied Environmental Research (ITM), Stockholm University, Stockholm, Sweden
Johan Ingri
Division of Applied Geology, Lulea University of Technology, Lulea, Sweden
Per Andersson
Laboratory for Isotope Geology, Swedish Museum of Natural History, Stockholm, Sweden
Oleg Dudarev
Pacific Oceanological Institute, Russian Academy of Science, Vladivostok, Russia
Daniel White
Water and Environmental Research Center, University of Alaska Fairbanks, Fairbanks, Alaska, USA
Abstract
Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the
Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were characterized for elemental composition (total organic
carbon, TOC, black carbon, BC, and total N, as well as major and trace elements), isotopic signature (δ13C, δ15N, Δ14C, ɛNd, 87Sr/86Sr), and organic molecular composition to better understand river export variations over the large spatial scale of the Siberian
Arctic. On average, 79 ± 9% of the total C in sediments was organic while 21 ± 9% was inorganic. BC made up 9 ± 4% of the
TOC pool, with a general increasing trend from west to east along the Siberian coast. The combined Nd- and Sr-isotopes (ɛNd and 87Sr/86Sr) were used to define two distinct sediment sources between east and west Siberian regions with the Khatanga River as a
boundary. Data from pyrolysis-GC/MS of the sedimentary organic carbon (SOC) indicated an increase in the freshness of the
organic matter from west to east on the Siberian Arctic coast, with increasing relative abundance of furfurals (polysaccharides)
with respect to nitriles. Values for the δ13C of SOC ranged from −27.1‰ (mostly terrigenous) to −23.8‰, while δ15N increased from east to west (3.1 to 5.2‰) with a significant correlation with C/N ratio. Values for the Δ14C of SOC ranged from −805 to −279‰, with a consistent trend increasing from the east (Indigirka River) to the west (Ob River).
These Δ14C values corresponded to a 14C age of 2570 ± 30 yBP in the Ob estuary and 13,050 ± 50 yBP in the Indigirka estuary. Most importantly, Δ14C values were significantly correlated with the ratio of BC/TOC (R2 = 0.91, n = 6), consistent with the distribution pattern of increasing permafrost zone from the west to the east along the
Siberian coast. Together, our results suggest that older OC was derived from the release of recalcitrant BC during permafrost
thawing and riverbank and coastal erosion, likely enhanced by ongoing environmental changes in the northern ecosystem.
Received 29
April
2003;
accepted 7
January
2004;
published 10
March
2004.
Index Terms: 1040 Geochemistry: Isotopic composition/chemistry; 1055 Geochemistry: Organic geochemistry; 1615 Global Change: Biogeochemical processes (4805); 4806 Oceanography: Biological and Chemical: Carbon cycling.
Read Full Article (file size: 532368 bytes) Cited by
Citation: Guo, L., I. Semiletov, Ö. Gustafsson, J. Ingri, P. Andersson, O. Dudarev, and D. White
(2004),
Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export,
Global Biogeochem. Cycles,
18,
GB1036,
doi:10.1029/2003GB002087.
Copyright 2004 by the American Geophysical Union.
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