FN Archimer Export Format
PT J
TI Transient early diagenetic processes in Rhône prodelta sediments revealed in contrasting flood events
BT 
AF PASTOR, Lucie
   RABOUILLE, C.
   METZGER, E.
   DE CHANVALON, A. Thibault
   VIOLLIER, E.
   DEFLANDRE, B.
AS 1:1;2:2;3:3;4:4;5:5;6:6;
FF 1:PDG-REM-EEP-LEP;2:;3:;4:;5:;6:;
C1 IFREMER Ctr Bretagne, REM EEP, Lab Environm Profond, F-29280 Plouzane, France.
   CEA, CNRS, Lab Mixte, Lab Sci Clinmat & Environm, Av Terrasse, F-91190 Gif Sur Yvette, France.
   Univ Angers, CNRS, UMR 6112, LPGN BIAF Lab Bioindicateurs Actuels & Fossiles, F-49045 Angers, France.
   Univ Delaware, Sch Marine Sci & Policy, Lewes, DE 19958 USA.
   Univ Paris Diderot, Sorbonne Paris Cite, Inst Phys Globe Paris, Geochim Eaux,UMR 7154, F-75005 Paris, France.
   Univ Bordeaux, EPOC, OASU, UMR 5805, Allee Geoffroy St Hilaire,CS50023, F-33615 Pessac, France.
C2 IFREMER, FRANCE
   CEA, FRANCE
   UNIV ANGERS, FRANCE
   UNIV DELAWARE, USA
   UNIV PARIS 07, FRANCE
   UNIV BORDEAUX, FRANCE
SI BREST
SE PDG-REM-EEP-LEP
IN WOS Ifremer jusqu'en 2018
   copubli-france
   copubli-univ-france
   copubli-int-hors-europe
IF 2.134
TC 10
UR https://archimer.ifremer.fr/doc/00449/56049/57568.pdf
   https://archimer.ifremer.fr/doc/00449/56049/57569.pdf
   https://archimer.ifremer.fr/doc/00449/56049/57651.pdf
LA English
DT Article
AB Floods carry sediments to river deltas and the coastal zone, but little is known about the geochemical evolution of this particulate material deposited over a short period of time. Here, we studied two recent contrasting flood deposits in the Rhône River prodelta area (northwestern Mediterranean Sea). We monitored the porewater and solid-phase chemistry over periods ranging from a few days to 6 months after deposition. Non-steady state diagenetic processes associated with episodic deposition promote a wide spectrum of transient redox conditions in the shallow prodelta region of the Rhône. Specific attributes of diagenetic responses depend on the sources of flood material and scale (thickness) of deposition. The first flood unit of 20–30 cm was composed of light gray mud, poor in organic carbon and rich in reactive manganese oxides. The short-term responses of early diagenetic processes contrasted with a rapid consumption of O2 and NO3- over a few hours just after the deposition event, accompanied by a slower build-up of Mn2+ concentration, and a lagged response in Fe2+ concentration over a few days or weeks. This difference was due to the redox capacity of the sediment, evolving from oxidized, during the flood layer deposition, to more reducing conditions, after a few days or weeks, allowing Fe2+ to build up and remain in solution. Sulfate reduction may have started within a few days within the flood deposit and was greatly enhanced just below the former redox front due to a fresh input of organic matter (OM). This large production of H2S probably led to the precipitation of sulfide minerals in close vicinity to the former redox front, limiting the accumulation of Fe2+ and H2S. The unit was sampled repeatedly three times during the six months following the flood event, and showed that manganese oxides were reduced at a rate of 1.8 mmol m−2 d−1, whereas the iron oxide concentration did not vary substantially. The second flood unit was composed of darker sediment, rich in organic carbon and reactive manganese oxides. The first step of OM degradation was enhanced within this dark deposit with a high release of dissolved organic carbon (DOC). A peak in Mn2+ concentration was also measured in association with the peak in reactive manganese oxides, also showing the rapid reduction of manganese after an input of fresh reactive oxides, and its potential increased release into the water column. Finally, a peak in nitrate concentration appeared in the sediment porewater within this anoxic organic/manganese-rich layer, likely resulting from the anaerobic oxidation of ammonium by manganese oxides. 
PY 2018
PD AUG
SO Continental Shelf Research
SN 0278-4343
PU Pergamon-elsevier Science Ltd
VL 166
UT 000443669300007
BP 65
EP 76
DI 10.1016/j.csr.2018.07.005
ID 56049
ER

EF