Marked isotopic variability within and between the Amazon River and marine dissolved black carbon pools

• Published in: Nature communications Vol. 10; no. 1; pp. 4018 - 8
• Main Authors: Coppola, Alysha I., Seidel, Michael, Ward, Nicholas D., Viviroli, Daniel, Nascimento, Gabriela S., Haghipour, Negar, Revels, Brandi N., Abiven, Samuel, Jones, Matthew W., Richey, Jeffrey E., Eglinton, Timothy I., Dittmar, Thorsten, Schmidt, Michael W. I.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.09.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 140/58; 704/47; 704/47/4113; Amazon; aquatic; atmospheric; biogeochemistry; Black carbon; burning; Byproducts; Carbon; carbon compound; Carbon cycle; carbon cycling; Carbon dioxide; Charcoal; chromophoric; climate change; coastal; continuum; Cycles; decomposition; Dissolved organic carbon; Dissolved organic matter; disturbance; ecosystem; emission; ENVIRONMENTAL SCIENCES; estuarine; export; fire; global change; gradients; Humanities and Social Sciences; hydrology; interface; marine; metabolism; multidisciplinary; organic carbon; organic matter; pyrogenic; pyrogenic carbon; river; Rivers; Science; Science (multidisciplinary); terrestial aquatic interface; terrestrial; tidal; tidal river; transition; Tributaries; tropical; tropics; Variability; Amazon River
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-11543-9

Riverine dissolved organic carbon (DOC) contains charcoal byproducts, termed black carbon (BC). To determine the significance of BC as a sink of atmospheric CO 2 and reconcile budgets, the sources and fate of this large, slow-cycling and elusive carbon pool must be constrained. The Amazon River is a significant part of global BC cycling because it exports an order of magnitude more DOC, and thus dissolved BC (DBC), than any other river. We report spatially resolved DBC quantity and radiocarbon (Δ 14 C) measurements, paired with molecular-level characterization of dissolved organic matter from the Amazon River and tributaries during low discharge. The proportion of BC-like polycyclic aromatic structures decreases downstream, but marked spatial variability in abundance and Δ 14 C values of DBC molecular markers imply dynamic sources and cycling in a manner that is incongruent with bulk DOC. We estimate a flux from the Amazon River of 1.9–2.7 Tg DBC yr −1 that is composed of predominately young DBC, suggesting that loss processes of modern DBC are important. Black carbon produced by the burning of biomass and fuels is the most stable carbon compound in nature, yet its path from land to the deep ocean where it persists for thousands of years remains mysterious. Here Coppola and colleagues characterize the black carbon exported by the Amazon River, the largest river in the world.