Stable carbon isotopic composition of oceanic dissolved black carbon reveals non-riverine source
Abstract
While the significance of charcoal cycling on land has long been recognized, the role of dissolved black carbon (DBC) as a major component of aquatic carbon cycles is still rapidly developing. We seek new approaches for identifying and tracking sources of DBC in aquatic systems. This is a challenging task, given that several environmental processes can significantly alter more commonly used source-specific DBC molecular signatures. Stable carbon isotopic signatures (δ13C) can vary with different organic matter sources and are consistent over time, assuming fractionation processes during DBC diagenesis do not occur. Here, we use compound-specific stable carbon isotopes of DBC-derived molecular markers (benzenepolycarboxylic acids) to constrain the source of DBC in the ocean. Based upon mass balance estimates, rivers are considered to be the main source of oceanic DBC. However, we reveal oceanic DBC to be consistently and significantly enriched in 13C compared to DBC in global rivers. These data indicate oceanic DBC is not predominantly derived from rivers. Instead, DBC in the ocean appears to derive from a non-riverine and isotopically distinct pool of condensed aromatics, raising fundamental questions regarding sources and processing of DBC across the land-ocean continuum. Potential non-riverine sources of oceanic DBC and drivers of this isotopic discrepancy will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B41A..04W
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0486 Soils/pedology;
- BIOGEOSCIENCES;
- 0496 Water quality;
- BIOGEOSCIENCES;
- 1807 Climate impacts;
- HYDROLOGY