25th International Meeting on Organic Geochemistry IMOG 2011

P-035
Contrasting macromolecular organic matter composition in
surface sediments off the Eurasian Arctic Rivers
Ayca Dogrul Selver 1,2 , Christopher Varden 1,2 , Igor Semiletov 3,4 , Örjan Gustafsson 5,6 ,
Steve Boult 1,2 , Bart E. van Dongen 1,2
1 School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M13
9PL, United Kingdom, 2 Williamson Research Centre for Molecular Environmental Science, University of
Manchester, Manchester,M13 9PL, United Kingdom, 3 <strong>International</strong> Arctic Research Center, University of
Alaska, P.O. Box 757340, Fairbanks, AK, 99775, United States of America, 4 Pacific Oceanological Institute,
Far-East Branch of Russian Academy of Science, Vladivostok 690041, Russian Federation, 5 Department of
Applied Environmental Science (ITM), Stockholm University,SE-10691, Stockholm, Sweden, 6 Bert Bolin
Center for Climate Research,SE-10691, Stockholm, Sweden (corresponding
author:ayca.dogrulselver@postgrad.manchester.ac.uk)
Recent climate observations indicate that the largest
effect of global warming is to be expected in the
Arctic, containing half of the global soil carbon [3], yet
this is currently one of the most understudied regions
of the globe. Warming could cause an increase in
active layer depth, enlarging of taliks, and general
reduction of the total volume of permafrost. Recent
studies, suggest that this might also change the input
fluxes, the radiocarbon age and the composition of
the terrestrial organic carbon (terrOC) remobilized to
the Eurasian Arctic Shelf [1]. However, little is known
about changes in the macromolecular terrOC
component.
To improve our understanding of climate warming on
the remobilization of the macromolecular terrOC
sediment samples from five Great Russian Arctic
River estuaries (GRARs) [1] were analysed by py-GC-
MS. In addition, obtaining information on the fate of
the remobilized terrOC is also of major importance.
Therefore sediments from a transect off the Kalix
River (northern Sweden) were also analyzed. This
transect is used because of the geochemical similarity
between the Kalix river and the western GRARs Ob
and Yenisey [2].
Analyses indicate that all pyrolysates were dominated
by four main classes of compounds; furfurals, alkylbenzenes,
nitriles and phenols (Fig. 1). The results
indicate substantial differences of the relative
contributions to the macromolecular terrOC between
the west (Ob, Yenisey & Kalix) and the east (Lena,
Indigirka, and Kolyma) (Fig. 1B). Furfurals
(Polysaccharide moieties) are relatively more
abundant in the western region pyrolysates (19% to
33%) than in the eastern region (4 to18%). In contrast
an opposite trend for the phenols (probably primarily
protein derived) can be observed (30 to 34% in the
west and 37 to 44% in the east). Considering
discontinuous or island permafrost coverage in the
western region and a continuous permafrost coverage
in the drainage basins of the eastern rivers, these
results could indicate a difference in the type of
material released due to the presence/absence of
permafrost.
Analyses of the Kalix River transect indicate a relative
increase in furfurals (from 23% to 36%) but a relative
decrease in phenols (from 41 to 30%) off the river
(Fig. 1A). These results support the idea that the
phenols predominantly originate from relatively labile
terrOC sources (e.g. proteins) and are preferentially
degraded along the transect.
Taken together, this study suggests resolvable
differences between the macromolecular terrOC
composition across the west-east set of five GRARs
as well as in the Kalix River transect. These
differences may assist in predicting how the
composition and the biogeochemical fate of the
macromolecular terrOC may change if the climate in
the eastern Russian-Arctic region becomes more like
that in the western part.
Fig. 1. Percent total index of terrOC composition in A)
Kalix River Transect Sediments and B) GRAR estuary
sediments.
References
[1] van Dongen, B.E. et al. Global Biogeochem.
Cycles 22, GB1011 (2008).
[2] Vonk, J.E. et al. Mar. Chem. 112, 1-10 (2008).[3]
Tarnocai, C. et al Global Biogeochem. Cycles 23,
GB2223 (2009).
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