Carbon-14 cycling in a nuclearized river: A first study in the downstream part of the Rhône River (France).

Carbon-14 (C) has a natural origin but is also anthropogenically released from civil nuclear facilities. Due to its long decay period (half-life: 5700 ± 30 years), it is a persistent radionuclide in the environment. In rivers, the complex speciation of carbon makes the fate of industrial C difficult to track.

Temporal trajectories of artificial radiocaesium Cs in French rivers over the nuclear era reconstructed from sediment cores.

Cs is a long-lived man-made radionuclide introduced in the environment worldwide at the early beginning of the nuclear Era during atmospheric nuclear testing's followed by the civil use of nuclear energy. Atmospheric fallout deposition of this major artificial radionuclide was reconstructed at the scale of French large river basins since 1945, and trajectories in French nuclearized rivers were established using sediment coring. Our results show that Cs contents in sediments of the studied rivers display a large spatial and temporal variability in response to the various anthropogenic pressures exerted on their catchment.

Temporal trends of plastic additive contents in sediment cores of three French rivers (Loire, Meuse and Moselle) over the last decades.

Sediment cores from three major French watersheds (Loire, Meuse and Moselle) have been dated by Cs and Pb from 1910 (Loire), 1947 (Meuse) and 1930 (Moselle) until the present in order to reconstruct trajectories of plastic additive contaminants including nine phthalate esters (PAEs) and seven organophosphate esters (OPEs), measured by gas chromatography-mass spectrometer (GC-MS-MS). Historical levels of ∑PAEs were higher than those of ∑OPEs in the Loire and the Moselle sediments, while ∑PAEs and ∑OPEs contents were of the same order of magnitude in the Meuse sediments. Although increases in concentrations do not evolve linearly, our results clearly indicate an increase in OPEs and PAEs concentrations from the 1950-1970 period onwards, compared with the first half of the 20th century.

Temporal evolution of plastic additive contents over the last decades in two major European rivers (Rhone and Rhine) from sediment cores analyses.

Although global plastic distribution is at the heart of 21st century environmental concerns, little information is available concerning how organic plastic additives contaminate freshwater sediments, which are often subject to strong anthropogenic pressure. Here, sediment core samples were collected in the Rhone and the Rhine watersheds (France), dated using Cs and Pb methods and analysed for nine phthalates (PAEs) and seven organophosphate esters (OPEs). The distribution of these organic contaminants was used to establish a chronological archive of plastic additive pollution from 1860 (Rhine) and 1930 (Rhone) until today.

Effects of climate variability changes on runoff and erosion in the Western European Loess Belt region (NW, France).

Runoff and soil erosion are very pronounced in the Western European Loess Belt. In this study, the distributed physically-based model CLiDE is calibrated, validated, and applied to a catchment of this area (Dun, NW, France) to assess the hydro-sedimentary impacts of climate change scenarios. Despite considerable progress over the last decade in the study of runoff and soil erosion in the context of climate change, the effects of changes in the temporal variability of precipitation remain poorly understood, especially at the scale of a river basin.

Shifts in sediment bacterial communities reflect changes in depositional environments in a fluviatile context.

Sediments are complex heterogeneous matrices allowing to some extent the recording of past environmental conditions by integrating sediment characteristics, contamination and the microbial community assembly. In aquatic environments, abiotic environmental filtering is considered the primary deterministic mechanism shaping microbial communities in sediments. However, the number and relative contributions of geochemical and physical factors associated with biotic parameters (reservoir of microorganisms) complicate our understanding of community assembly dynamics.

Hydrological classification by clustering approach of time-integrated samples at the outlet of the Rhône River: Application to ΔC-POC.

Within the framework of the Rhône Sediment Observatory, monthly time-integrated samples have been collected by Particle Traps in the last decade to monitor particulate contaminants in the Rhône River and its main tributaries. In this watershed with a contrasted hydrology, a clustering approach is used to classify the samples according to the main hydrological events. This approach has been applied to riverine particulate organic radiocarbon signatures (ΔC-POC) that are strongly affected by the origin of the material and the occurrence of nuclear power plant releases.

The unravelling of radiocarbon composition of organic carbon in river sediments to document past anthropogenic impacts on river systems.

As carriers of dissolved and particulate loads that connect continental surfaces to oceans, river systems play a major role in the global carbon cycle. Indeed, riverine particulate organic carbon (POC) is a melange of various origins characterized by their own C labeling. In addition, civil nuclear activities have brought new C source that remains poorly documented.

Historical and post-ban releases of organochlorine pesticides recorded in sediment deposits in an agricultural watershed, France.

Agricultural use of organochlorine pesticides (OCPs) increased during the twentieth century but many of them have been progressively banned several decades after their introduction. Nevertheless, these lipophilic chemical compounds may persist in soils and sediments. From sediment deposits, it is possible to reconstruct the chronology of OCP releases in relation to former applications through time.

Flux estimation, temporal trends and source determination of trace metal contamination in a major tributary of the Seine estuary, France.

Anthropogenic impacts on rivers have increased significantly over the past ~150 years, particularly at the beginning of the industrial revolution. Among other signs, this impact is manifested through the addition of trace metals and metalloid elements to rivers. The Eure River watershed in France covers an area of 6017 km and is a major tributary of the Seine estuary.

Evidence for tritium persistence as organically bound forms in river sediments since the past nuclear weapon tests.

Tritium of artificial origin was initially introduced to the environment from the global atmospheric fallout after nuclear weapons tests. Its level was increased in rainwaters by a factor 1000 during peak emissions in 1963 within the whole northern hemisphere. Here we demonstrate that tritium from global atmospheric fallout stored in sedimentary reservoir for decades as organically bound forms in recalcitrant organic matter while tritium released by nuclear industries in rivers escape from such storages.

A brief history of origins and contents of Organically Bound Tritium (OBT) and C in the sediments of the Rhône watershed.

Tritium (H) and Carbon-14 (C) are radionuclides of natural (cosmogenic) origin that have also been introduced into the environment by humans since the middle of the last century. They are therefore not compounds that have only recently been released into the environment and they do not pose a recognized health threat due to their low radiotoxicity. However, they hold an important place among current concerns because they are being discharged into the environment by the nuclear industry in large quantities compared to other radionuclides.

Occurrence of 1,1'-dimethyl-4,4'-bipyridinium (Paraquat) in irrigated soil of the Lake Chad Basin, Niger.

Increased use of agrochemical products to improve yields for irrigated crops in sub-Saharan Africa has been accompanied by a significant increase in the risk of environmental contamination. Detailed examples of the fate of pesticides after initial spreading on crop fields are scarce in tropical regions, where safe practices and related health risks are poorly understood by smallholder farmers. In the semi-arid environment of the Lake Chad Basin, SE Niger, both intrinsic properties of pesticides and extrinsic factors such as soil and climate helped to characterize processes leading to an accumulation of pesticides in soils.

Nutrient dynamics at the sediment-water interface in a Mediterranean lagoon (Thau, France): influence of biodeposition by shellfish farming activities.

The Thau Lagoon, a French Mediterranean shallow lagoon, is a site where extensive shellfish farming occurs. The aim of the present work is to evaluate the role of this activity on nutrient exchange at the sediment-water interface in relation to organic matter (OM) sedimentation and degradation. Two stations inside (C5) and outside (C4) of the shellfish farming areas were sampled at three seasons.