Letter | Published:

Reburial of fossil organic carbon in marine sediments

Abstract

Marine sediments act as the ultimate sink for organic carbon, sequestering otherwise rapidly cycling carbon for geologic timescales1,2. Sedimentary organic carbon burial appears to be controlled by oxygen exposure time in situ3,4, and much research has focused on understanding the mechanisms of preservation of organic carbon5. In this context, combustion-derived black carbon has received attention as a form of refractory organic carbon that may be preferentially preserved in soils6,7 and sediments8,9. However, little is understood about the environmental roles, transport and distribution of black carbon. Here we apply isotopic analyses to graphitic black carbon samples isolated from pre-industrial marine and terrestrial sediments. We find that this material is terrestrially derived and almost entirely depleted of radiocarbon, suggesting that it is graphite weathered from rocks, rather than a combustion product. The widespread presence of fossil graphitic black carbon in sediments has therefore probably led to significant overestimates of burial of combustion-derived black carbon in marine sediments. It could be responsible for biasing radiocarbon dating of sedimentary organic carbon, and also reveals a closed loop in the carbon cycle. Depending on its susceptibility to oxidation, this recycled carbon may be locked away from the biologically mediated carbon cycle for many geologic cycles.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1

    Hedges, J. I. & Keil, R. G. Sedimentary organic matter preservation: an assessment and speculative synthesis. Mar. Chem. 49, 81–115 (1995)

  2. 2

    Berner, R. A. Biogeochemical cycles of carbon and sulfur and their effect on atmospheric oxygen over Phanerozoic time. Palaeogeogr. Palaeoclimatol. Palaeoecol. 75, 97–122 (1989)

  3. 3

    Hartnett, H. E., Keil, R. G., Hedges, J. I. & Devol, A. H. Influence of oxygen exposure time on organic carbon preservation in continental margin sediments. Nature 391, 572–574 (1998)

  4. 4

    Hedges, J. I. et al. Sedimentary organic matter preservation: a test for selective degradation under oxic conditions. Am. J. Sci. 299, 529–555 (1999)

  5. 5

    Hedges, J. I. et al. The molecularly-uncharacterized component of nonliving organic matter in natural environments. Org. Geochem. 31, 945–958 (2000)

  6. 6

    Skjemstad, J. O., Taylor, J. A. & Smernik, R. J. Estimation of charcoal (char) in soils. Commun. Soil Sci. Plant Anal. 30, 2283–2298 (1999)

  7. 7

    Schmidt, M. W. I., Skjemstad, J. O., Gehrt, E. & Kögel-Knabner, I. Charred organic carbon in German chernozemic soils. Eur. J. Soil Sci. 50, 351–365 (1999)

  8. 8

    Gélinas, Y., Prentice, K. M., Baldock, J. A. & Hedges, J. I. An improved thermal oxidation method for the quantification of soot/graphitic black carbon in sediments and soils. Environ. Sci. Technol. 35, 3519–3525 (2001)

  9. 9

    Middleburg, J. J., Nieuwenhuize, J. & van Breugel, P. Black carbon in marine sediments. Mar. Chem. 65, 245–252 (1999)

  10. 10

    Goldberg, E. D. Black Carbon in the Environment: Properties and Distribution (Wiley & Sons, New York, 1985)

  11. 11

    Schmidt, M. W. I. & Noack, A. G. Black carbon in soils and sediments: analysis, distribution, implications, and current challenges. Glob. Biogeochem. Cycles 14, 777–793 (2000)

  12. 12

    Masiello, C. A. & Druffel, E. R. M. Black carbon in deep-sea sediments. Science 280, 1911–1913 (1998)

  13. 13

    Carpenter, R., Beasley, T. M., Zahnle, D. & Somayajulu, B. L. K. Cycling of fallout (Pu, 241Am, 137Cs) and natural (U, Th, 210Pb) radionuclides in Washington continental slope sediments. Geochim. Cosmochim. Acta 51, 1897–1921 (1987)

  14. 14

    Prahl, F. G. & Carpenter, R. Hydrocarbons in Washington coastal sediments. Estuar. Coast. Shelf Sci. 18, 703–720 (1984)

  15. 15

    Vogel, J. S., Nelson, D. E. & Southon, J. R. C-14 background levels in an Accelerator Mass Spectrometry system. Radiocarbon 29, 323–333 (1987)

  16. 16

    Stuiver, M. & Polach, H. A. Reporting of 14C data. Radiocarbon 19, 355–363 (1977)

  17. 17

    Wakeham, S. G. et al. Hydrocarbons in Lake Washington sediments: a 25-year retrospective in an urban lake. Environ. Sci. Technol. (in the press)

  18. 18

    Wakeham, S. G., Lee, C., Hedges, J. I., Hernes, P. J. & Peterson, M. L. Molecular indicators of diagenetic status in marine organic matter. Geochim. Cosmochim. Acta 61, 5363–5369 (1997)

  19. 19

    Eglinton, T. I. et al. Composition, age and provenance of organic matter in NW African dust over the Atlantic Ocean. Geochem. Geophys. Geosyst. 3, 1–27 (2002)

  20. 20

    Weis, P. L. The origin of epigenetic graphite: evidence from isotopes. Geochim. Cosmochim. Acta 45, 2325–2332 (1981)

  21. 21

    Schidlowski, M. Carbon isotopes as biogeochemical recorders of life over 3.8 Ga of Earth history: evolution of a concept. Precambr. Res. 106, 117–134 (2001)

  22. 22

    Petsch, S. T., Smernik, R. J., Eglinton, T. I. & Oades, J. M. A solid-state 13C-NMR study of kerogen degradation during black shale weathering. Geochim. Cosmochim. Acta 65, 1867–1882 (2001)

  23. 23

    Herring, J. R. in The Carbon Cycle and Atmospheric CO2: Natural Variations, Archean to Present (eds Sundquist, E. T. & Broecker, W. S.) 419–442 (AGU, Washington, 1985)

  24. 24

    Suman, D. O., Kuhlbusch, T. A. J. & Lim, B. in Sediment Records of Biomass Burning and Global Change (ed. Clark, J. S.) 271–293 (Springer, Berlin, 1997)

  25. 25

    Sackett, W. M., Poag, C. W. & Eadie, B. J. Kerogen recycling in the Ross Sea, Antarctica. Science 185, 1045–1047 (1974)

  26. 26

    Blair, N. E. et al. The persistence of memory: the fate of ancient sedimentary organic carbon in a modern sedimentary system. Geochim. Cosmochim. Acta 67, 63–73 (2003)

  27. 27

    Eglinton, T. I. et al. Variability in radiocarbon ages of individual organic compounds from marine sediments. Science 277, 796–799 (1997)

  28. 28

    Petsch, S. T., Berner, R. A. & Eglinton, T. I. A field study of the chemical weathering of ancient sedimentary organic matter. Org. Geochem. 31, 475–487 (2000)

  29. 29

    Jahnke, R. A. The global ocean flux of particulate organic carbon: Areal distribution and magnitude. Glob. Biogeochem. Cycles 10, 71–88 (1996)

  30. 30

    Druffel, E. R. M., Williams, P. M., Livingston, H. D. & Koide, M. Variability of natural and bomb-produced radionuclide distributions in abyssal red clay sediments. Earth Planet. Sci. Lett. 71, 205–214 (1984)

Download references

Acknowledgements

We thank the scientific staff at the Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry for assistance with radiocarbon analyses, C. Preston and C. Swanston for radiocarbon analysis of the Stillaguamish River sample, S. Petsch and R. Smernik for providing kerogen samples for analysis, and P. Quay and E. Druffel for editing and comments. This work was supported by a mini-grant from LLNL CAMS and by grants from the NSF; A.F.D. thanks the NSF for a graduate research fellowship; Y.G. thanks the Canadian NSERC and Quebec NATEQ for support for this work.

Author information

Correspondence to Angela F. Dickens.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Supplementary information

Table 1: Kerogen sample information and graphitic black carbon (GBC) yield. (DOC 20 kb)

Rights and permissions

Reprints and Permissions

About this article

Further reading

Figure 1: Concentrations and fluxes of GBC off the Washington coast.
Figure 2: Plot of Δ versus δ13C for all TOC (open symbols) and GBC (closed symbols) samples.

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.