Schmidt Michael W. I.

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Schmidt
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Michael W. I.
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  • Preprint
    Global-scale evidence for the refractory nature of riverine black carbon
    ( 2018-05) Coppola, Alysha I. ; Wiedemeier, Daniel B. ; Galy, Valier ; Haghipour, Negar ; Hanke, Ulrich ; Nascimento, Gabriela S. ; Usman, Muhammed ; Blattmann, Thomas M. ; Reisser, Moritz ; Freymond, Chantal V. ; Zhao, Meixun ; Voss, Britta M. ; Wacker, Lukas ; Schefuß, Enno ; Peucker-Ehrenbrink, Bernhard ; Abiven, Samuel ; Schmidt, Michael W. I. ; Eglinton, Timothy I.
    Wildfires and incomplete combustion of fossil fuel produce large amounts of black carbon. Black carbon production and transport are essential components of the carbon cycle. Constraining estimates of black carbon exported from land to ocean is critical, given ongoing changes in land use and climate, which affect fire occurrence and black carbon dynamics. Here, we present an inventory of the concentration and radiocarbon content (∆14C) of particulate black carbon for 18 rivers around the globe. We find that particulate black carbon accounts for about 15.8 ± 0.9% of river particulate organic carbon, and that fluxes of particulate black carbon co-vary with river-suspended sediment, indicating that particulate black carbon export is primarily controlled by erosion. River particulate black carbon is not exclusively from modern sources but is also aged in intermediate terrestrial carbon pools in several high-latitude rivers, with ages of up to 17,000 14C years. The flux-weighted 14C average age of particulate black carbon exported to oceans is 3,700 ± 400 14C years. We estimate that the annual global flux of particulate black carbon to the ocean is 0.017 to 0.037 Pg, accounting for 4 to 32% of the annually produced black carbon. When buried in marine sediments, particulate black carbon is sequestered to form a long-term sink for CO2.
  • Article
    Decoupled sedimentary records of combustion : causes and implications
    (John Wiley & Sons, 2016-05-30) Hanke, Ulrich ; Eglinton, Timothy I. ; Braun, Ana L. L. ; Reddy, Christopher M. ; Wiedemeier, Daniel B. ; Schmidt, Michael W. I.
    Pyrogenic carbon (PyC) is a collective term for carbon-rich residues comprised of a continuum of products arising from biomass burning and fossil-fuel combustion. PyC is ubiquitous in the environment where it can be transported by wind and water before being deposited in aquatic sediments. We compare results from four different methods used to trace PyC that were applied to a high-temporal resolution sedimentary record in order to constrain changes in PyC concentrations and fluxes over the past ~250 years. We find markedly discordant records for different PyC tracers, particularly during the preindustrial age, implying different origins and modes of supply of sedimentary PyC. In addition to providing new insights into the composition of sedimentary combustion products, this study reveals that elucidation of past combustion processes and development of accurate budgets of PyC production and deposition on local to regional scales requires careful consideration of both source characteristics and transport processes.