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Origin and processing of terrestrial organic carbon in the Amazon system: Lignin phenols in river, shelf, and fan sediments

Publication ,  Journal Article
Sun, S; Schefuß, E; Mulitza, S; Chiessi, CM; Sawakuchi, AO; Zabel, M; Baker, PA; Hefter, J; Mollenhauer, G
Published in: Biogeosciences
May 17, 2017

The Amazon River transports large amounts of terrestrial organic carbon (OCterr) from the Andean and Amazon neotropical forests to the Atlantic Ocean. In order to compare the biogeochemical characteristics of OCterr in the fluvial sediments from the Amazon drainage basin and in the adjacent marine sediments, we analysed riverbed sediments from the Amazon mainstream and its main tributaries as well as marine surface sediments from the Amazon shelf and fan for total organic carbon (TOC) content, organic carbon isotopic composition (δ13CTOC), and lignin phenol compositions. TOC and lignin content exhibit positive correlations with Al/Si ratios (indicative of the sediment grain size) implying that the grain size of sediment discharged by the Amazon River plays an important role in the preservation of TOC and leads to preferential preservation of lignin phenols in fine particles. Depleted δ13CTOC values (-26.1 to -29.9%) in the main tributaries consistently correspond with the dominance of C3 vegetation. Ratios of syringyl to vanillyl (S/V) and cinnamyl to vanillyl (C/V) lignin phenols suggest that non-woody angiosperm tissues are the dominant source of lignin in the Amazon basin. Although the Amazon basin hosts a rich diversity of vascular plant types, distinct regional lignin compositions are not observed. In the marine sediments, the distribution of δ13CTOC and Λ8 (sum of eight lignin phenols in organic carbon (OC), expressed as mg/100ĝ€mg OC) values implies that OCterr discharged by the Amazon River is transported north-westward by the North Brazil Current and mostly deposited on the inner shelf. The lignin compositions in offshore sediments under the influence of the Amazon plume are consistent with the riverbed samples suggesting that processing of OCterr during offshore transport does not change the encoded source information. Therefore, the lignin compositions preserved in these offshore sediments can reliably reflect the vegetation in the Amazon River catchment. In sediments from the Amazon fan, low lignin content, relatively depleted δ13CTOC values and high (Ad/Al)V ratios indicating highly degraded lignin imply that a significant fraction of the deposited OCterr is derived from petrogenic (sourced from ancient rocks) sources.

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Published In

Biogeosciences

DOI

EISSN

1726-4189

ISSN

1726-4170

Publication Date

May 17, 2017

Volume

14

Issue

9

Start / End Page

2495 / 2512

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 4104 Environmental management
  • 3709 Physical geography and environmental geoscience
  • 3103 Ecology
  • 06 Biological Sciences
  • 05 Environmental Sciences
  • 04 Earth Sciences
 

Citation

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Sun, S., Schefuß, E., Mulitza, S., Chiessi, C. M., Sawakuchi, A. O., Zabel, M., … Mollenhauer, G. (2017). Origin and processing of terrestrial organic carbon in the Amazon system: Lignin phenols in river, shelf, and fan sediments. Biogeosciences, 14(9), 2495–2512. https://doi.org/10.5194/bg-14-2495-2017
Sun, S., E. Schefuß, S. Mulitza, C. M. Chiessi, A. O. Sawakuchi, M. Zabel, P. A. Baker, J. Hefter, and G. Mollenhauer. “Origin and processing of terrestrial organic carbon in the Amazon system: Lignin phenols in river, shelf, and fan sediments.” Biogeosciences 14, no. 9 (May 17, 2017): 2495–2512. https://doi.org/10.5194/bg-14-2495-2017.
Sun S, Schefuß E, Mulitza S, Chiessi CM, Sawakuchi AO, Zabel M, et al. Origin and processing of terrestrial organic carbon in the Amazon system: Lignin phenols in river, shelf, and fan sediments. Biogeosciences. 2017 May 17;14(9):2495–512.
Sun, S., et al. “Origin and processing of terrestrial organic carbon in the Amazon system: Lignin phenols in river, shelf, and fan sediments.” Biogeosciences, vol. 14, no. 9, May 2017, pp. 2495–512. Scopus, doi:10.5194/bg-14-2495-2017.
Sun S, Schefuß E, Mulitza S, Chiessi CM, Sawakuchi AO, Zabel M, Baker PA, Hefter J, Mollenhauer G. Origin and processing of terrestrial organic carbon in the Amazon system: Lignin phenols in river, shelf, and fan sediments. Biogeosciences. 2017 May 17;14(9):2495–2512.

Published In

Biogeosciences

DOI

EISSN

1726-4189

ISSN

1726-4170

Publication Date

May 17, 2017

Volume

14

Issue

9

Start / End Page

2495 / 2512

Related Subject Headings

  • Meteorology & Atmospheric Sciences
  • 4104 Environmental management
  • 3709 Physical geography and environmental geoscience
  • 3103 Ecology
  • 06 Biological Sciences
  • 05 Environmental Sciences
  • 04 Earth Sciences