American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 532368 bytes)    Cited by

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.