| Autor: |
Dellinger M; Department of Geography, Durham University, Durham DH1 3LE, United Kingdom.; Environnement, Dynamique et Territoires de Montagne, CNRS-University Savoie Mont Blanc, Le Bourget du Lac 73373, France., Hilton RG; Department of Geography, Durham University, Durham DH1 3LE, United Kingdom.; Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom., Baronas JJ; Department of Earth Sciences, Durham University, Durham DH1 3LE, United Kingdom., Torres MA; Department of Earth, Environmental, and Planetary Sciences, Rice University, Houston, TX 77005., Burt EI; Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089., Clark KE; Department of Geography & Planning, University of Liverpool, Liverpool L69 7ZT, United Kingdom., Galy V; Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543., Ccahuana Quispe AJ; Escuela Profesional de Biologia, Facultad de Ciencas, Universidad Nacional de San Antonio Abad del Cusco, Cusco 08000, Peru., West AJ; Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089. |
| Abstrakt: |
The oxidation of organic carbon contained within sedimentary rocks ("petrogenic" carbon, or hereafter OC petro ) emits nearly as much CO 2 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 OC petro oxidation. However, these settings also export unweathered material that may continue to react in downstream floodplains. The relative importance of OC petro 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 OC petro 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 OC petro oxidation and that this proportion increases downstream. We estimate that in the Andes, OC petro oxidation releases 11.2 +4.5 / -2.8 tC km -2 y -1 of CO 2 , which corresponds to ~41% of the total OC petro denudation (sum of oxidized and solid OC petro ). A Re mass balance across the Rio Madre de Dios shows that 46% of OC petro oxidation takes place in the Andes, 14% in the foreland-lowlands, and 40% in the Andean-fed floodplains. This doubling of OC petro oxidation flux downstream of the Andes demonstrates that, when present, floodplains can greatly increase OC petro oxidation and CO 2 release. |
