Concentrations and fluxes of suspended particulate matters and associated contaminants in the Rhône River from Lake Geneva to the Mediterranean Sea

The Rhône River is amongst the main rivers of Western Europe and the biggest by freshwater discharge and sediment delivery to the Mediterranean Sea. Its catchment is characterized by distinct hydrological regimes that may produce annual sediment deliveries ranging from 1.4 to 18.0 Mt y−1. Furthermore, the course of the Rhône River meets numerous dams, hydro- and nuclear power plants, and agricultural, urban or industrial areas. Thus, suspended particulate matters (SPM) have been involved in the fate of hydrophobic contaminants such as polychlorobiphenyls (PCB), mercury (Hg) and other trace metal elements (TME), and radionuclides for decades. To investigate the concentrations and the fluxes of SPM and associated contaminants, as well as their sources, a monitoring network of 15 stations (three on the Rhône River and 12 on tributaries, from Lake Geneva to the Mediterranean Sea) has been set up in the past decade within the Rhône Sediment Observatory (OSR). A main purpose of this observatory is to assess the long term trend of the main contaminant concentrations and fluxes, and to understand their behavior during extreme events such as floods or dam flushing operations. The dataset presented in this paper contains the concentrations and fluxes of SPM as well as the concentrations and fluxes of several particle bound contaminants of concern (PCB, TME, radionuclides), the particle size distribution and the particulate organic carbon of SPM. Sediment traps or continuous flow centrifuges were used to collect sufficient amount of SPM in order to conduct the measurements. This observatory is on-going since 2011 and the database is regularly updated. All the data are made publicly available in French and English through the BDOH/OSR database at https://doi.org/10.15454/RJCQZ7 (Lepage et al., 2021).

Historical cartographic and topo-bathymetric database on the French Rhône River (17th–20th century)

Space and time analyses of channel changes, especially within large rivers subject to high levels of human impact, are critical to address multiple questions about rivers in the Anthropocene era. The reconstruction of long-term (> 150 year) evolutionary trajectories permits an understanding of how natural and anthropogenic factors impact hydromorphological and ecological processes in rivers, helps with the design of sustainable management and restoration options, and may also help in the assessment of future changes. However, the reconstruction of channel changes can be challenging: historical data are often scattered across many archives, and the quantity and accuracy of information generally decreases as one goes back in time. This data article provides a historical database of 350 cartographic and topo-bathymetric resources on the French Rhône River (530 km in length) compiled from the 17th to mid-20th century, with a temporal focus prior to extensive river training (1860s). The data were collected in 14 national, regional, and departmental archive services. A table describes the properties of each archived data item and its associated iconographic files. Some of the historical maps are available in a georeferenced format. A GIS layer enables one-click identification of all archive data available for a given reach of the French Rhône River. This database provides substantial new material for deeper analyses of channel changes over a longer time period and at a finer time step compared with previously available data. The database has several potential applications in geomorphology, retrospective hydraulic modelling, historical ecology, and river restoration, as well as permitting comparisons with other multi-impacted rivers worldwide. The dataset is available at https://doi.org/10.1594/PANGAEA.922437 (Arnaud et al., 2020a). Iconographic extracts of the 350 archived items are available at http://photo.driihm.fr/index.php/category/52 (last access: 2 May 2021).

Evaluating river driftwood potential for energy storage applications

<p>Around the world rivers transport large volumes of driftwood into lakes, seas and oceans. Recruited commonly during flooding events and transported by rivers, driftwood poses a hazard for the point of view of the safety of infrastructures and river dwellers. For that reason, it is many times extracted locally and stored; driftwood removal prevents sinking and protects the dam infrastructure. Collected driftwood is a neglected river resource that is generally combusted or landfilled. Génissiat dam on the Rhone River in France presents a case study where annually approximately 1300 tons of driftwood is intersected.</p><p> </p><p>Among the different processes that are capable of converting driftwood, HydroThermal Carbonization (HTC) is of high interest due its ability to process biomass with high moisture content, such as driftwood. HTC of biomass leads to the production of a solid product referred to as hydrochar, which is a high added-value material that can be used in different applications, such as fuel cooking, soil amendment, water treatment and energy storage. The goal of the study was to characterize the driftwood collected upstream of the Génissiat dam and to investigate its potential for hydrochar production as precursor of anode in sodium-ion batteries. Sodium-ion batteries have received more interest lately as an alternative for the resource intensive and expensive lithium-ion batteries.  The study follows a novel approach in study driftwood by categorizing based on their genera. HTC of the different identified genera was conducted in a 2L batch reactor following a temperature of 200 °C for a residence time of 11.5 h. Results show that the impact of driftwood genera is not significant for processing of driftwood through HTC. Produced hydrochar had a high carbon content (from 55.4 to 57.0 %) and lower ash content (from 0.2 to 1.4 \% of dry biomass). Electrochemical results show that driftwood-based hydrochar is a promising precursor of hard carbon anodes in sodium-ion batteries due to its excellent electrochemical performance.</p><p><strong> </strong></p><p><strong>Key words</strong>: Driftwood, Hydrothermal carbonization, Hydrochar, Rhone river, Sodium-ion batteries</p>

Spatial Distributions of Surface Sedimentary Organics and Sediment Profile Image Characteristics in a High-Energy Temperate Marine RiOMar: The West Gironde Mud Patch

The spatial distributions of (1) surface sediment characteristics (D0.5, Sediment Surface Area (SSA), Particulate Organic Carbon (POC), Chlorophyll-a (Chl-a), Phaeophytin-a (Phaeo-a), Total and Enzymatically Hydrolyzable Amino Acids (THAA, EHAA), δ13C) and (2) sediment profile image (apparent Redox Potential Discontinuity (aRPD), numbers and depths of biological traces) characteristics were quantified based on the sampling of 32 stations located within the West Gironde Mud Patch (Bay of Biscay, NE Atlantic) in view of (1) assessing the spatial structuration of a temperate river-dominated ocean margin located in a high-energy area, (2) disentangling the impacts of hydrodynamics and bottom trawling on this structuration, and (3) comparing the West Gironde Mud Patch with the Rhône River Prodelta (located in a low-energy area). Results support the subdivision of the West Gironde Mud Patch in a proximal and a distal part and show (1) the existence of depth gradients in surface sedimentary organics characteristics and bioturbation within the distal part; (2) no evidence for a significant effect of bottom trawling, as opposed to Bottom Shear Stress, on the West Gironde Mud Patch spatial structuration; and (3) major discrepancies between spatial structuration in the West Gironde Mud Patch and the Rhône River Prodelta, which were attributed to differences in tidal regimes, sedimentation processes, and local hydrodynamics, which is in agreement with current river-dominated ocean margin typologies.