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Hemingway, Jordon D; Schefuß, Enno; Dinga, Bienvenu Jean; Pryer, Helena; Galy, Valier V (2016): Concentrations and d13C compositions of n-alkanes, n-alcohols, n-alkanoic acids in a 34-month time series of suspended sediments from the outflow of the Congo River. PANGAEA, https://doi.org/10.1594/PANGAEA.864152, Supplement to: Hemingway, JD et al. (2016): Multiple plant-wax compounds record differential sources and ecosystem structure in large river catchments. Geochimica et Cosmochimica Acta, 184, 20-40, https://doi.org/10.1016/j.gca.2016.04.003

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Abstract:
The concentrations, distributions, and stable carbon isotopes (d13C) of plant waxes carried by fluvial suspended sediments contain valuable information about terrestrial ecosystem characteristics. To properly interpret past changes recorded in sedimentary archives it is crucial to understand the sources and variability of exported plant waxes in modern systems on seasonal to inter-annual timescales. To determine such variability, we present concentrations and d13C compositions of three compound classes (n-alkanes, n-alcohols, n-alkanoic acids) in a 34-month time series of suspended sediments from the outflow of the Congo River.
We show that exported plant-dominated n-alkanes (C25-C35) represent a mixture of C3 and C4 end members, each with distinct molecular distributions, as evidenced by an 8.1 ± 0.7 per mil (±1Sigma standard deviation) spread in d13C values across chain-lengths, and weak correlations between individual homologue concentrations (r = 0.52-0.94). In contrast, plant-dominated n-alcohols (C26-C36) and n-alkanoic acids (C26-C36) exhibit stronger positive correlations (r = 0.70-0.99) between homologue concentrations and depleted d13C values (individual homologues average <= -31.3 per mil and -30.8 per mil, respectively), with lower d13C variability across chain-lengths (2.6 ± 0.6 per mil and 2.0 ± 1.1 per mil, respectively). All individual plant-wax lipids show little temporal d13C variability throughout the time-series (1 Sigma <= 0.9 per mil), indicating that their stable carbon isotopes are not a sensitive tracer for temporal changes in plant-wax source in the Congo basin on seasonal to inter-annual timescales.
Carbon-normalized concentrations and relative abundances of n-alcohols (19-58% of total plant-wax lipids) and n-alkanoic acids (26-76%) respond rapidly to seasonal changes in runoff, indicating that they are mostly derived from a recently entrained local source. In contrast, a lack of correlation with discharge and low, stable relative abundances (5-16%) indicate that n-alkanes better represent a catchment-integrated signal with minimal response to discharge seasonality. Comparison to published data on other large watersheds indicates that this phenomenon is not limited to the Congo River, and that analysis of multiple plant-wax lipid classes and chain lengths can be used to better resolve local vs. distal ecosystem structure in river catchments.
Coverage:
Latitude: -4.310000 * Longitude: 15.230000
Date/Time Start: 2010-11-01T00:00:00 * Date/Time End: 2013-08-01T00:00:00
Size:
8 datasets

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Datasets listed in this publication series

  1. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA1) Environmental parameters of the Congo River recorded near Brazzaville/Kinshasa during the sampling period from November 2010 to August 2013. https://doi.org/10.1594/PANGAEA.864091
  2. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA2) Concentrations of n-alkanes, average chain lengths, and carbon preference indices in a 34-month time series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864099
  3. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA3) Concentrations of n-alcohols, average chain lengths, and carbon preference indices in a 34-month time series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864107
  4. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA4) Concentrations of n-alkanoic acids, average chain lengths, and carbon preference indices in a 34-month time series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864135
  5. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA5) d13C measurements of n-alkane in a 34-month time series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864137
  6. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA6) d13C measurements of n-alcohol in a 34-month time series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864147
  7. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA7) d13C measurements of n-alkanoic acid in a 34-month time series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864150
  8. Hemingway, JD; Schefuß, E; Dinga, BJ et al. (2016): (Table EA8) Relative compound class contributions to total n-alkyl lipids in a 34-month time-series of suspended sediments from the outflow of the Congo River. https://doi.org/10.1594/PANGAEA.864151