The fate of river organic carbon in coastal areas: A study in the Rhone River delta using multiple isotopic (delta C-13, Delta C-14) and organic tracers

Type Article
Date 2013-10
Language English
Author(s) Cathalot Cecile1, Rabouille Christophe1, Tisnerat-Laborde N.1, Toussaint Flora1, Kerherve P.2, 3, Buscail R.2, 3, Loftis K.4, Sun M. -Y.4, Tronczynski Jacek5, Azoury S., Lansard Bruno1, Treignier Claire1, Pastor L.6, Tesi T.7, 8
Affiliation(s) 1 : UVSQ, CNRS, CEA, Lab Sci Climat & Environm, Gif Sur Yvette, France.
2 : CNRS, Ctr Format & Rech Environm Mediterraneens, UMR 5110, F-66860 Perpignan, France.
3 : Univ Perpignan, Ctr Format & Rech Environm Mediterraneens, UMR 5110, F-66860 Perpignan, France.
4 : Univ Georgia, Dept Marine Sci, Athens, GA 30602 USA.
5 : IFREMER, Lab Biogeochim Contaminants Organ, Nantes, France.
6 : Univ Paris 07, Lab Geochim Eaux, Paris, France.
7 : ISMAR CNR UOS Bologna, Ist Sci Marine, I-40129 Bologna, Italy.
8 : Stockholm Univ, Inst Appl Environm Res ITM, S-10691 Stockholm, Sweden.
Source Geochimica Et Cosmochimica Acta (0016-7037) (Pergamon-elsevier Science Ltd), 2013-10 , Vol. 118 , P. 33-55
DOI 10.1016/j.gca.2013.05.001
WOS© Times Cited 45
Abstract A significant fraction of the global carbon flux to the ocean occurs in River-dominated Ocean Margins (RiOMar) although large uncertainties remain in the cycle of organic matter (OM) in these systems. In particular, the OM sources and residence time have not been well clarified. Surface (0-1 cm) and sub-surface (3-4 cm) sediments and water column particles (bottom and intermediate depth) from the Rhone River delta system were collected in June 2005 and in April 2007 for a multi-proxy study. Lignin phenols, black carbon (BC), proto-kerogen/BC mixture, polycyclic aromatic hydrocarbons (PAHs), carbon stable isotope (delta C-13(OC)), and radiocarbon measurements (delta C-14(OC)) were carried out to characterize the source of sedimentary organic material and to address degradation and transport processes. The bulk OM in the prodelta sediment appears to have a predominantly modern terrigenous origin with a significant contribution of modern vascular C-3 plant detritus (Delta C-14(OC) = 27.9 parts per thousand, delta C-13(OC) = -27.4 parts per thousand). In contrast, the adjacent continental shelf, below the river plume, seems to be dominated by aged OM (Delta C-14(OC) = -400 parts per thousand, delta C-13(OC) = -24.2 parts per thousand), and shows no evidence of dilution and/or replacement by freshly produced marine carbon. Our data suggest an important contribution of black carbon (50% of OC) in the continental shelf sediments. Selective degradation processes occur along the main dispersal sediment system, promoting the loss of a modern terrestrial OM but also proto-kerogen-like OM. In addition, we hypothesize that during the transport across the shelf, a long term resuspension/deposition loop induces efficient long term degradation processes able to rework such refractory-like material until the OC is protected by the mineral matrix of particles.
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Cathalot Cecile, Rabouille Christophe, Tisnerat-Laborde N., Toussaint Flora, Kerherve P., Buscail R., Loftis K., Sun M. -Y., Tronczynski Jacek, Azoury S., Lansard Bruno, Treignier Claire, Pastor L., Tesi T. (2013). The fate of river organic carbon in coastal areas: A study in the Rhone River delta using multiple isotopic (delta C-13, Delta C-14) and organic tracers. Geochimica Et Cosmochimica Acta, 118, 33-55. Publisher's official version : https://doi.org/10.1016/j.gca.2013.05.001 , Open Access version : https://archimer.ifremer.fr/doc/00157/26784/