Badlands as a hot spot of petrogenic contribution to riverine particulate organic carbon to the Gulf of Lion (NW Mediterranean Sea)

Abstract

Determining the riverine carbon fluxes to oceans is critical for an improved understanding of C budgets and biogeochemical cycles (C, O) over a broad range of spatial and time scales. Among the particulate organic carbon (POC) involved in these fluxes, those yielded by sedimentary rocks (petrogenic POC: pPOC) remain somewhat uncertain as to their source on continental surfaces. Based on time series from long‐term observatories, we refine the POC and sediments flux of the Rhône River, one of the major tributaries to the Mediterranean Sea. Radiocarbon measurements on a set of riverine samples and forward modelling were used to (i) determine a modelled pPOC content and pPOC/POC ratio for each sample set, (ii) assess pPOC flux delivered to the NW Mediterranean Sea, and (iii) estimate the badlands contribution from the Durance catchment to both the pPOC and to sediment discharges. The weighted pPOC flux contributes up to 26% of the POC flux (145 Gg yr‐1) discharged into the Mediterranean Sea, whereas the weighted pPOC content reaches 0.31 wt%. Despite their low contributive surface area (0.2%), badlands provide, respectively, 12, 3.5 and 14% of the pPOC, POC and sediment fluxes to the Rhône River. Consequently, such rocks can be considered as a major source of pPOC and sediments for the NW Mediterranean Sea and potentially for oceans. We suggest that river‐dominated ocean margins, such as the Rhône River, with badlands in their catchment could export a significant amount of pPOC to the oceans. Copyright © 2018 John Wiley & Sons, Ltd.

Spatio-temporal assessment of the polychlorinated biphenyl (PCB) sediment contamination in four major French river corridors (1945–2018)

“…For the calculation of specific PCBi flux, we estimated sediment flux according to water discharge (m 3 s −1 ; available at http://www.hydro.eaufrance.fr, last access: 14 January 2020) and reconstructed SPM concentrations using rating curves (relationships between water discharge and measured SPM concentrations). Specific rating curves were used for each river according to the existing literature and based on previously published data (Garonne - Coynel et al, 2004;Loire -Moatar and Dupont, 2016;Rhône -Poulier et al, 2019;Seine -GIP Seine Aval, 2008). This calculation was achieved at the gauging stations located just upstream of tidal influence zones (see locations in Fig.…”

“…The water engineering column refers to groups defined in the text. SPMsuspended particulate matterdischarges were based on existing literature (Copard et al, 2018;Coynel et al, 2004;GIP Seine Aval, 2008;Moatar and Dupont, 2016;Poulier et al, 2019). of Biscay) in western Europe.…”

Spatio-temporal assessment of the PCB sediment contamination in the four main French River Basins (1945–2018)

“…The water-engineering column refers to groups defined in the text. SPM -Suspended Particulate Matters -discharges were based on existing literature (Moatar et al, 2006;Copard et al, 2018;Descy et al, 2009;Olivier et al, 2009). https://doi.org/10.5194/essd-2019-167 MacDonald et al, 2000).…”

Trajectories of technogenic tritium in the Rhône River (France)

“…It drains a catchment area of 97 800 km2 and it is the most important river in France in terms of water discharge with an annual average flow of 1700 m3 s-1 at 60 km from the mouth. Its annual solid discharge ranges from 1.2 to 22.7 million tons per year between 1971 and 2016 (Copard et al, 2018;Pont et al, 2002;Poulier et al, 2019;Sempere et al, 2000), and up to 80% of the total amount of discharge delivered to Mediterranean Sea occurs during floods episodes (Antonelli et al, 2004). The Rhône River is highly industrialized and characterized among other various industries by the presence of 21 hydropower plants, four nuclear power plants, and a spent fuel reprocessing center (Marcoule) in dismantlement since 1997.…”