Dellinger Mathieu

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Dellinger
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Mathieu
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  • Preprint
    Erosion of organic carbon in the Arctic as a geological carbon dioxide sink
    ( 2015-05-12) Hilton, Robert G. ; Galy, Valier ; Gaillardet, Jerome ; Dellinger, Mathieu ; Bryant, Charlotte ; O'Regan, Matt ; Grocke, Darren R. ; Coxall, Helen ; Bouchez, Julien ; Calmels, Damien
    Soils of the northern high latitudes store carbon over millennial timescales (103 yrs) and contain approximately double the carbon stock of the atmosphere1-3. Warming and associated permafrost thaw can expose soil organic carbon and result in mineralisation and carbon dioxide (CO2) release4-6. However, some of this soil organic carbon may be eroded and transferred to rivers7-9. If it escapes degradation during river transport and is buried in marine sediments, then it can contribute to a longer-term (>104 yrs), geological CO2 sink8-10. Despite this recognition, the erosional flux and fate of particulate organic carbon (POC) in large rivers at high latitudes remains poorly constrained. Here, we quantify POC source in the Mackenzie River, the main sediment supplier to the Arctic Ocean11,12 and assess its flux and fate. We combine measurements of radiocarbon, stable carbon isotopes and element ratios 26 to correct for rock-derived POC10,13,14. Our samples reveal that the eroded biospheric POC has resided in the basin for millennia, with a mean radiocarbon age of 5800±800 yr, much older than large tropical rivers13,14. Based on the measured biospheric POC content and variability in annual sediment yield15, we calculate a biospheric POC flux of 𝟐. 𝟐𝟐−𝟎𝟎.𝟗𝟗 +𝟏𝟏.𝟑𝟑 TgC yr-1 from the Mackenzie River, three times the CO2 drawdown by silicate weathering16. Offshore we find evidence for efficient terrestrial organic carbon burial over the Holocene, suggesting that erosion of organic carbon-rich, high latitude soils may result in a significant geological CO2 sink.
  • Article
    High rates of rock organic carbon oxidation sustained as Andean sediment transits the Amazon foreland-floodplain
    (National Academy of Sciences, 2023-09-19) Dellinger, Mathieu ; Hilton, Robert G. ; Baronas, J. Jotautas ; Torres, Mark A. ; Burt, Emily I. ; Clark, Kasey E. ; Galy, Valier ; Quispe, Adan J.C. ; West, A. Joshua
    The oxidation of organic carbon contained within sedimentary rocks (“petrogenic” carbon, or hereafter OCpetro) emits nearly as much CO2 as is released by volcanism, thereby playing a key role in the long-term global C budget. High erosion rates in mountains have been shown to increase OCpetro oxidation. However, these settings also export unweathered material that may continue to react in downstream floodplains. The relative importance of OCpetro oxidation in mountains versus floodplains remains difficult to assess as disparate methods have been used in the different environments. Here, we investigate the sources and fluxes of rhenium (Re) in the Rio Madre de Dios to quantify OCpetro oxidation from the Andes to the Amazon floodplain using a common approach. Dissolved rhenium concentrations (n = 131) range from 0.01 to 63 pmol L−1 and vary depending on lithology and geomorphic setting. We find that >75% of the dissolved Re derives from OCpetro oxidation and that this proportion increases downstream. We estimate that in the Andes, OCpetro oxidation releases 11.2+4.5/−2.8 tC km−2 y−1 of CO2, which corresponds to ~41% of the total OCpetro denudation (sum of oxidized and solid OCpetro). A Re mass balance across the Rio Madre de Dios shows that 46% of OCpetro oxidation takes place in the Andes, 14% in the foreland-lowlands, and 40% in the Andean-fed floodplains. This doubling of OCpetro oxidation flux downstream of the Andes demonstrates that, when present, floodplains can greatly increase OCpetro oxidation and CO2 release.