Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis-gas chromatography-mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial phenols, aromatics and cyclopentenones to marine pyridines. There is good agreement between proportion phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r2 Combining double low line 0.67, p < 0.01, n Combining double low line 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (14COC) which, when coupled with previous measurements, allows us to produce the most comprehensive 14COC map of the ESAS to date. Combining the 14COC and py-GCMS data suggests that the aromatics group of compounds is likely sourced from old, aged terrOC, in contrast to the phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of phenols and pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and it shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastal-erosion-dominated to marine-dominated signatures.
School of Earth and Environmental Sciences, Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester, United Kingdom; School of Science and the Environment, Manchester Metropolitan University, Manchester, United Kingdom; Ballkesir University, Geological Engineering Department, Ballkesir, Turkey; Department of Environmental Science and Analytical Chemistry (ACES), Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden; Pacific Oceanological Institute, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, Russian Federation; International Arctic Research Center, University of Alaska, Fairbanks, United States; National Tomsk Research Polytechnic University, Tomsk, Russian Federation; Geological Institute, ETH Zurich, Zurich, Switzerland; Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland; School of Civil Engineering and Geosciences, Newcastle University, Newcastle, United Kingdom
Recommended Citation:
Sparkes R,B,, Selver A,et al. Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf[J]. Cryosphere,2016-01-01,10(5)