Seine River Basin Research Articles

The first catchment water balance: New insights into Pierre Perrault, his perceptual model and his peculiar catchment

ABSTRACT Pierre Perrault and his 1674 book De l’Origine des Fontaines are widely acknowledged in hydrology as the first formal articulation of the catchment water balance based on field data. Many summaries of his work have now been written, but few of these summaries have examined Perrault’s perceptual model in detail and none that we are aware of have gone back to his study catchment to collect new data in which to frame these historic findings in a modern context. Here we report new insights (with re-calculations of some of his analyses) into Perrault’s work, his perceptual model of streamflow generation and his rather peculiar 119 km2 headwater catchment of the Seine River basin. We show the uncertainty of his flow and catchment area estimates, some errors in perception about hydrological flowpaths and new age estimates for the spring-fed site where he worked. Despite these modern criticisms and updates, Perrault’s place in hydrological history is secure: he was the first to bring quantitative analysis to fundamental questions of the terrestrial water cycle.

Bayesian inversion of bacterial physiology and dissolved organic carbon biodegradability on water incubation data

In aquatic ecosystems, dissolved organic carbon (DOC) plays a significant role in the global carbon cycle. Microorganisms mineralize biodegradable DOC, releasing greenhouse gases (carbon dioxide, methane) into the atmosphere. Extensive research has focused on the concentrations and biodegradability of DOC in aquatic systems worldwide. However, little attention has been given to uncertainties regarding the physiological characteristics of heterotrophic bacteria, which are crucial for biogeochemical modeling. In this study, the physiological properties of heterotrophic bacteria and the properties of DOC biodegradability in water are inferred through a Bayesian inversion approach. To achieve this, treated and natural water samples collected from the Seine River basin, were inoculated and incubated in laboratory. During incubation, the concentrations of DOC and heterotrophic bacteria biomass were measured. Then, a multiple Monte Carlo Markov Chains method and the HSB model (High-weight polymers, Substrate, heterotrophic Bacteria) are applied on the water incubation data. The results indicate a higher biodegradable fraction of DOC in natural water compared to treated water and significant variability in the fraction of fast biodegradable DOC within 5 days in both water samples. The significant variability highlights the uncertainties/challenges in the HSB model parameterization. The seven water samples used in the paper serve as a proof of concept. They are from various origins and display the potential of the method to identify parameter values in a large range of values. Because mortality rate of heterotrophic bacteria at 20 ∘C (kd20) showed a remarkable stability at 0.013 h−1, we considered that this parameter can be fixed at this value. The maximum growth rates at 20 ∘C (μmax20) was 0.061 h−1 while optimal growth yield (Y) estimated at 0.34 for treated water and at 0.25 for natural water. All these parameter values are well in accordance with previous determinations.

Environmental controls on the distribution of brGDGTs and brGMGTs across the Seine River basin (NW France): implications for bacterial tetraethers as a proxy for riverine runoff

Abstract. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial lipids that have been widely used as environmental proxies in continental paleorecords. Another group of related lipids, branched glycerol monoalkyl glycerol tetraethers (brGMGTs), has recently been proposed as a potential paleotemperature proxy. Nevertheless, the sources and environmental dependencies of both brGDGTs and brGMGTs along the river–sea continuum are still poorly understood, complicating their application as paleoenvironmental proxies in some aquatic settings. In this study, the sources of brGDGTs and brGMGTs and the potential factors controlling their distributions are explored across the Seine River basin (NW France), which encompasses the freshwater-to-seawater continuum. BrGDGTs and brGMGTs were analyzed in soils, suspended particulate matter (SPM), and sediments (n=237) collected along the land–sea continuum of the Seine basin. Both types of compounds (i.e., brGDGTs and brGMGTs) are shown to be produced in situ, in freshwater and saltwater, based on their high concentrations and distinct distributions in aquatic settings (SPM and sediments) vs. soils. Redundancy analysis further shows that both salinity and nitrogen dominantly control the brGDGT distributions. Furthermore, the relative abundance of 6-methyl vs. that of 5-methyl brGDGTs (the IR6Me ratio), the total nitrogen (TN), the δ15N, and the chlorophyll a concentration co-vary in a specific geographical zone with low salinity, suggesting that 6-methyl brGDGTs are preferentially produced under low-salinity and high-productivity conditions. In contrast to brGDGTs, the brGMGT distribution appears to be primarily regulated by salinity, with a distinct influence on the individual homologues. Salinity is positively correlated with homologues H1020a and H1020b and negatively correlated with compounds H1020c and H1034b in SPM. This suggests that bacteria living in freshwater preferentially produce compounds H1020c and H1034b, whereas bacteria that primarily grow in saltwater appear to be predominantly responsible for the production of homologues H1020a and H1020b. Based on the abundance ratio of the freshwater-derived compounds (H1020c and H1034b) vs. their saltwater-derived homologues (H1020a and H1020b), a novel proxy, the Riverine IndeX (RIX), is proposed to trace riverine organic matter inputs, with high values (>0.5) indicating a higher riverine contribution. We successfully applied RIX to the Godavari River basin (India) and a paleorecord across the upper Paleocene and lower Eocene from the Arctic Coring Expedition at Lomonosov Ridge, showing its potential applicability to both modern samples and paleorecords.

The water-agro-food system: upscaling from the Seine river basin to the global scale

The water-agro-food system: upscaling from the Seine river basin to the global scale

The Seine River Basin

La serie de libros dedicada a la química ambiental publicados por Springer con acceso gratuito, con el objetivo el difundir estudios ambientales acerca de los cambios, impactos y riesgos que generan las actividades realizadas, por las poblaciones que habitan un territorio delimitado por un parámetro geográfico como el de una cuenca.El libro sirve de referencia para la caracterización cartográfica y ambiental de otras cuencas hidrográficas, debido al importante número de urbes que fueron construidas, pobladas, desforestadas e impactadas por las actividades humanas desarrolladas cerca a sus afluentes.

Probability-Based Rule Curves for Multi-Purpose Reservoir System in the Seine River Basin, France

Multiple reservoir operation is of paramount importance due to tradeoffs in water supply and their cost functions. Understanding this complexity is important for optimizing water supply and increasing synergies gained from the joint operation. Therefore, this study aimed to develop a conceptual framework for addressing the effects of climate change on water security under the operating rules of the multiple reservoir system in northern France. A dynamic programming approach (DP) was employed to find the cost–benefit analysis that best fit with the objectives of reservoir operation, while the space rule was applied to balance the available space in each reservoir of a parallel system. A finite-horizon optimal regulation was then adopted for determining daily reservoir storage based on probability-based rule curves. The results indicated that the predicted inflow during the drawdown–refill cycle period to the Marne and Pannecière reservoirs would be the largest and lowest, respectively. The proposed upper rule curves during high-flow conditions suggested that the release from Aube reservoir should be postponed from July to August until September. At 50- and 100-year return periods, quite a high release rate from Seine and Marne reservoirs was observed during the dry season. A decrease in future water supply from Pannecière reservoir was found during summer, while the withdrawal in November could cause excessive water in the Seine tributary and Paris City. Under low-flow conditions in all return periods, the proposed lower rule curves recommended that the reservoir storage should go below the current operating rule, with a clear difference in July (the largest in Marne and the smallest in Pannecière) and almost no difference in November. Moreover, the web-based support system IRMaRA was developed for revising operating rules of four main reservoirs located in the Seine River Basin. The novelty of this modeling framework would contribute to the practice of deriving optimal operating rules for a multi-reservoir system by the probability-based rule curve method. Based on the evaluation of the effects of applying the estimated reservoir storage capacity under different return periods, both less overflow and water shortage represented by different levels of quantity and severity can be expected compared to the existing target storage at specified control points. Finally, the obtained finding revealed that the application of dynamic programming for reservoir optimization would help in developing a robust operating policy for tackling the effects of climate change.

Hydraulic modeling of a large-scale sanitary system in river flood conditions. Application to the Seine river basin

Cet article présente une étude de cas pour évaluer les interactions entre un grand système d’assainissement et une crue entraînant des débordements, sur la base d’une modélisation hydraulique. L’étude de cas présentée ici est réalisée sur le réseau d’assainissement de la zone centrale de l’Île-de-France, confrontée à une inondation majeure le long du bassin de la Seine et de la Marne. Ce réseau joue un rôle majeur de protection contre les inondations en évacuant les flux excédentaires des précipitations, de l’aquifère et des débordements directs des rivières. Il peut néanmoins également induire une aggravation des inondations en cas de saturation des postes de pompage ou de défaillance d’équipements. Le présent document décrit les étapes de construction et de calage du modèle sur la base des données disponibles pour les crues de janvier 2018 et de juin 2016. Ce modèle repose sur l’utilisation de la plateforme logicielle Hydra/Qgis. L’accent est mis sur l’ajustement des apports supplémentaires du fleuve et de l’aquifère dans le système d’assainissement, ainsi que sur la précision et les performances de calcul du modèle. L’objectif final de ce projet est d’évaluer la résilience des réseaux d’assainissement sur la zone de collecte étudiée et de produire un outil d’aide à la décision pour améliorer la gestion du système d’assainissement en période de crue, en considérant les dommages potentiels en fonction du niveau d’inondation.

Regional coupled surface–subsurface hydrological model fitting based on a spatially distributed minimalist reduction of frequency domain discharge data

Abstract. Although integrated water resource models are indispensable tools for water management at various scales, it is of primary importance to ensure their proper fitting on hydrological variables, avoiding flaws related to equifinality. An innovative stepwise fitting methodology is therefore proposed, which can be applied for any river basin model, from catchment to continental scale as far as hydrological models or land surface models are concerned. The methodology focuses on hydrosystems considering both surface water and groundwater, as well as internal water fluxes such as river baseflow. It is based on the thorough analysis of hydrological signal transformation by various components of a coupled surface–subsurface hydrosystem in a nested approach that considers the conditionality of parameter fields on their input forcing fluxes. The methodology is based on the decomposition of hydrological signal in the frequency domain with the HYMIT (HYdrological MInimalist Transfer function) method (Schuite et al., 2019). Parameters derived from HYMIT are used to fit the coupled surface–subsurface hydrological model CaWaQS3.02 using a stepwise methodology, which relies on successive Markov chain Monte Carlo optimizations related to various objective functions representing the dependency of the hydrological parameter fields on forcing input fluxes. This new methodology enables significant progress to be made in terms of the spatial distribution of the model parameters and the water balance components at the regional scale. The use of many control stations such as discharge gauging stations with HYMIT leads to a coarse parameter distribution that is then refined by the fitting of CaWaQS parameters on its own mesh. The stepwise methodology is exemplified with the Seine River basin (∼76 000 km2). In particular, it made it possible to spatially identify fundamental hydrological values, such as rainfall partitioning into actual evapotranspiration, as well as runoff and aquifer recharge through its impluvium, in both the time and frequency domains. Such a fitted model facilitates the analysis of both the overall and detailed territorial functioning of the river basin, explicitly including the aquifer system. A reference piezometric map of the upmost free aquifer units and a water budget of the Seine basin are established, detailing all external and internal fluxes up to the exchanges between the eight simulated aquifer layers. The results showed that the overall contribution of the aquifer system to the river discharge of the river network in the Seine basin varies spatially within a wide range (5 %–96 %), with an overall contribution at the outlet of the basin of 67 %. The geological substratum greatly influences the contribution of groundwater to the river discharge.

Bioaccumulation of per- and polyfluoroalkyl substance in fish from an urban river: Occurrence, patterns and investigation of potential ecological drivers

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in aquatic environments and a recent shift toward emerging PFAS is calling for new data on their occurrence and fate. In particular, understanding the determinants of their bioaccumulation is fundamental for risk assessment purposes. However, very few studies have addressed the combined influence of potential ecological drivers of PFAS bioaccumulation in fish such as age, sex or trophic ecology. Thus, this work aimed to fill these knowledge gaps by performing a field study in the Seine River basin (France). Composite sediment and fish (European chub, Squalius Cephalus) samples were collected from four sites along a longitudinal transect to investigate the occurrence of 36 PFAS. Sediment molecular patterns were dominated by fluorotelomer sulfonamidoalkyl betaines (i.e. 6:2 and 8:2 FTAB, 46% of ∑PFAS on average), highlighting the non-negligible contribution of PFAS of emerging concern. C9–C14 perfluoroalkyl carboxylic acids, perfluorooctane sulfonic acid (PFOS), perfluorooctane sulfonamide (FOSA) and 10:2 fluorotelomer sulfonate (10:2 FTSA) were detected in all fish samples. Conversely, 8:2 FTAB was detected in a few fish from the furthest downstream station only, suggesting the low bioaccessibility or the biotransformation of FTABs. ∑PFAS in fish was in the range 0.22–3.8 ng g−1 wet weight (ww) and 11–140 ng g−1 ww for muscle and liver, respectively. Fish collected upstream of Paris were significantly less contaminated than those collected downstream, pointing to urban and industrial inputs. The influence of trophic ecology and biometry on the interindividual variability of PFAS burden in fish was examined through analyses of covariance (ANCOVAs), with sampling site considered as a categorical variable. While the latter was highly significant, diet was also influential; carbon sources and trophic level (i.e. estimated using C and N stable isotope ratios, respectively) equally explained the variability of PFAS levels in fish.

Experimental study on river sediment incorporation in concrete as a full aggregate replacement: Technical feasibility and economic viability

The reuse of river sediments as aggregates is a sustainable management technique that reduces waste from dredging operations and offers the potential to realize economic benefits. This research aims to evaluate the technical feasibility and economic viability of producing C30 class concrete made from sediments. Sediment from the Seine River Basin is characterized from a physical, environmental and mineralogical perspective before its incorporation into concrete as full substitute for conventional aggregates. The physical, mechanical and durability properties as well as the leaching of these concretes are then investigated. Sediment characterization shows that the physical properties (i.e. density, water absorption, and particle size) are close to those of conventional aggregates. The environmental and mineralogical characterization has proven that the studied sediments are inert and are mainly silico-calcareous materials. Experimental results reveal that a slight increase in cement dosage (less than 5%) yields a sediment concrete possessing properties similar to those of the control specimen with any effects remaining only marginal. Leaching tests indicate that the rate of pollutants released by the sediment-based concrete is of the same order of magnitude as that released by the control specimen. The economic viability study has found that the production of a C30 concrete based on sediment is 41 % less expensive. In-situ use of sediments in concrete prevents the carbon footprint of aggregate transport, which offsets that of additional cement for sediments-based concrete.

Historical Changes in the Ecological Connectivity of the Seine River for Fish: A Focus on Physical and Chemical Barriers Since the Mid-19th Century

To understand the long-term fate of fish assemblages in the context of global change and to design efficient restoration measures in river management, it is essential to consider the historical component of these ecosystems. The human-impacted Seine River Basin is a relevant case that has experienced the extinction of diadromous fishes over the last two centuries and has recently witnessed the recolonization of some species. One key issue is to understand the historical evolution of habitat accessibility for these migratory species. Thanks to the unique availability of historical, mainly hand-written sources of multiple types (river engineering projects, navigation maps, paper-based databases on oxygen, etc.), we documented and integrated, in a geographic information system-based database, the changes to physical and chemical barriers in the Seine River from the sea to Paris for three time periods (1900s, 1970s, and 2010s). The potential impact of these changes on the runs of three migratory species that have different migratory behaviors—Atlantic salmon, allis shad, and sea lamprey—was evaluated by ecological connectivity modeling, using a least-cost approach that integrates distance, costs, and risks related to barriers. We found that accessibility was contrasted between species, emphasizing the crucial role of the migration type, period, and level of tolerance to low dissolved oxygen values. The highest disruption of ecological connectivity was visible in the 1970s, when the effects of large hypoxic areas were compounded by those of impassable navigation weirs (i.e., without fish passes). As the approach was able to reveal the relative contribution of physical and chemical barriers on overall functional connectivity, it may constitute a model work in assessing the functioning of large river ecosystems.

Innovative combination of tracing methods to differentiate between legacy and contemporary PAH sources in the atmosphere-soil-river continuum in an urban catchment (Orge River, France)

Polycyclic aromatic hydrocarbons (PAH) have been released by human activities during more than a century, contaminating the entire atmosphere – soil – river continuum. Due to their ubiquity in the environment and their potential severe biological impacts, PAH became priority pollutants and were targeted by environmental public agencies. To better manage PAH pollution, it is necessary to identify unambiguously the sources and pathways of those compounds at the catchment scale, and to evaluate the persistence of historical PAH pollution in the environment especially in those urban contexts concentrating multiple PAH sources. Accordingly, the current research monitored the contamination in atmospheric fallout, soils and rivers of a 950-km2 catchment (Orge River) characterized by an increasing urban gradient in downstream direction, and located in the Seine River basin characterized by a high level of PAH legacy contamination. A combination of various approaches was used, including the widely used PAH diagnostic ratios, together with innovative methods such as PAH correlations and sediment fingerprinting using fallout radionuclides to clearly identify both the origin of PAH and their main PAH pathways to the river. The results demonstrated the persistence of legacy PAH contamination in the catchment, responsible for the signature of the suspended particulate matter currently transiting in the Orge River. They underlined the conservation of PAH through the soil – river continuum. Finally, urban runoff was demonstrated to provide the main PAH source to the river in the densely urbanized area by both PAH correlations and sediment fingerprinting. These results were used to model PAH concentrations in those particles supplied from urban areas to the river.

An integrated framework to model nitrate contaminants with interactions of agriculture, groundwater, and surface water at regional scales: The STICS–EauDyssée coupled models applied over the Seine River Basin

Nutrient enrichment from natural and anthropogenic activities is one of the major environmental pollution stressors. This study presents an integrated framework that couples a mesoscale atmospheric analysis system (SAFRAN), an agronomic model (STICS) and a distributed hydro(geo)logic model (EauDyssée) to estimate nitrogen flux at the regional scale. The EauDyssée modeling framework was developed to include nitrate transport from soils to rivers via surface runoff and stream-aquifer interactions. Further, an in-stream nitrate model was developed based on the large-scale river routing of the framework. The utility of the integrated framework was demonstrated on the Seine River Basin (SRB), which has an area of 88,000 square kilometers. The SRB is one of the most productive agricultural areas in France and encompasses the megalopolis of Paris. This basin is a complex hydrosystem with multiple aquifers. The STICS-EauDyssée integrated framework was implemented for a long-term simulation covering 39 years (1971–2010) at a daily time step. Comparison of groundwater nitrate concentrations with observations showed an overall absolute bias of less than 10 mg/L. Model results showed that simulated nitrate flux to rivers highly depend on the inflow produced by surface and subsurface waters. Results also demonstrated that approximately 10% of leaching nitrate flux is delivered to the river network from stream-aquifer interactions. The statistical analysis indicates the modeling system performs better in the eastern region of the SRB in comparison to the western part of the basin, due to the hydrological complexity of the western part of the basin. Comparison of maximum nitrate concentration between dry and wet years (1990 and 2001) showed an increase of 60%, largely driven by more annual water yield in the wet year compared to the dry year.

Retrieving river baseflow from SWOT spaceborne mission

The quantification of aquifer contribution to river discharge is of primary importance to evaluate the impact of climatic and anthropogenic stresses on the availability of water resources. Several baseflow estimation methods require river discharge measurements, which can be difficult to obtain at high spatio-temporal resolution for large basins. The future Surface Water and Ocean Topography (SWOT) satellite mission will provide discharge estimations for large rivers (>50–100 m wide) even in ungauged basins. The frequency of these estimations depends mainly on latitude and ranges from zero to more than ten values in the 21-day satellite cycle. This work aims at answering the following question: can baseflow be estimated from SWOT observations during the mission lifetime? An algorithm based on hydrograph separation by Chapman's filter was developed to automatically estimate the baseflow in a river network at regional scale (>10 000 km2). The algorithm was applied to the Seine river basin (75 000 km2, France) using the discharge time series simulated at daily time step by a coupled hydrological-hydrogeological model to obtain the reference baseflow estimations. The same algorithm is then forced with discharge time series sampled at SWOT observation frequency. The average baseflow is estimated with good accuracy for all the reaches which are observed at least once per cycle (relative bias less than 8%). The time evolution of baseflow is also rather well retrieved, with a Nash-Sutcliffe coefficient above 0.7 for 96% of the network length. An analysis of the effect of SWOT discharge uncertainties on baseflow estimation shows that bias is the component of discharge error that most contributes to the error on baseflow. Anyway, when the combined effect of SWOT discharge sampling and SWOT discharge uncertainties is considered, the error on baseflow estimates is slightly smaller than that on discharge. This work provides new potential for the SWOT mission in terms of global hydrological analysis and water cycle closure.

Landward Perspective of Coastal Eutrophication Potential Under Future Climate Change: The Seine River Case (France)

Studies quantifying the impact of climate change have so far mostly examined atmospheric variables, and few are evaluating the cascade of aquatic impacts that will occur along the land–ocean continuum until the ultimate impacts on coastal eutrophication potential. In this study, a new hydro-biogeochemical modeling chain has been developed, based on the coupling of the generic pyNuts-Riverstrahler biogeochemical model and the GR4J-CEMANEIGE hydrological model, and applied to the Seine River basin (France). Averaged responses of biogeochemical variables to climate-induced hydrological changes were assessed using climate forcing based on twelve projections of precipitation and temperature (BC-CORDEX) for the stabilization (RCP 4.5) and the increasing (RCP 8.5) CO2 emission scenarios. Beyond the amount of nutrients delivered to the sea, we calculated the indicator of coastal eutrophication potential (ICEP). The models run with the RCP4.5 stabilization scenario show low variations in hydrological regimes and water quality, while five of the six models run with the increasing CO2 emissions scenario (RCP8.5) leads to more intense extreme streamflow (i.e., higher maximum flows, lower and longer minimum flows), resulting in the degradation of water quality. For the driest RCP 8.5 projection, median biogeochemical impacts induced by decreasing discharge (until -270 m3 s-1 in average) are mostly located downstream of major wastewater treatment plants. During spring bloom, e.g., in May, the associated higher residence time leads to an increase of phytoplankton biomass (+31% in average), with a simultaneous -23% decrease of silicic acid, followed downstream by a -9% decrease of oxygen. Later during low flow, major increases in nitrate and phosphate concentrations (until +19% and +32% in average) are expected. For all considered scenarios, high ICEP values (above zero) lasted, indicating that coastal eutrophication is not expected to decrease with changing hydrological conditions in the future. Maximum values are even expected to be higher some years. This study deliberately evaluates the impact of modified hydrology on biogeochemistry without considering the simultaneous alteration of water temperatures, in order to disentangle the causes of climate change-induced impact. It will serve as a first comparative step toward a more complete modeling experiment of climate change impacts on aquatic systems.

Investigating the metal contamination of sediment transported by the 2016 Seine River flood (Paris, France)

Fine sediment transport in rivers is exacerbated during flood events. These particles may convey various contaminants (i.e. metals, pathogens, industrial chemicals, etc.), and significantly impact water quality. The exceptional June 2016 flood of the Seine River (catchment area: 65 000 km2, France), potentially mobilized and deposited contaminated materials throughout the Paris region. Flood sediment deposits (n = 29) were collected along the Seine River and its main tributaries upstream (Yonne, Loing and Marne Rivers) and downstream of Paris (Oise and Eure Rivers). Fallout radionuclides (137Cs, 7Be) were measured to characterize the sources of the material transiting the river, while trace elements (e.g. Cr, Ni, Zn, Cu, As, Cd, Sb, Pb, Tl, Ag) and stable lead isotopes (206Pb/207Pb) were analyzed to quantify the contamination of sediment transported during the flood. In upper sections of the Seine River, sediment mainly originated from the remobilization of particles with a well-balanced contribution of surface and subsurface sources. In the upstream tributaries, sediment almost exclusively originated from the remobilization of subsurface particles. In Paris and downstream of Paris, recently eroded particles and surface sources dominated, suggesting particles were mainly supplied by urban runoff and the erosion of agricultural soils. The highest metal concentrations and Enrichment Factors (EF) were found in the sediment collected in the Loing, Orge and Yvette upstream tributaries. Although these inputs were diluted in the Seine River, an increase in elemental concentrations was observed, progressing downstream through Paris. However, EFs in sediment collected along the Seine River were lower or in the same range of values sampled over the last several decades, reflecting the progressive decontamination of the urbanized Seine River basin.

Are boron isotopes a reliable tracer of anthropogenic inputs to rivers over time?

This study aims at determining how the boron signal of the Seine River evolved in terms of concentration and isotopic signatures over eighteen years (1994–95 and 2006–12) and if boron isotopes can reliably trace anthropogenic inputs over time. In the anthropised Seine River watershed, boron is widely released by human activities, and even if boron concentrations ([B]) are below the potability limit, our study confirms the potential of boron isotopes (δ11B) to trace urban anthropogenic contaminations. Between 1994 and 2012, [B] have decreased across the anthropised part of the Seine River basin (and by a factor of two in Paris) while δ11B has increased. This means either that urban inputs have been reduced or that the boron signature of urban inputs has changed over time. Both hypotheses are in agreement with the decrease of perborate consumption in Europe over 15years and are not mutually exclusive.Results of a thorough analysis of urban effluents from the sewage network of Paris conurbation that are in fine released to the Seine River suggest a shift of the urban δ11B from −10‰ in 1994 to 1.5±2.0‰ in 2012, in agreement with our second hypothesis. We attribute this change to the removal of perborates from detergents rather than to the modernisation of wastewater treatment network, because it does not significantly impact the wastewater boron signatures. Eighteen years after the first assessment and despite the decreased use of perborates, geochemical and isotopic mass budgets confirm, that boron in the Seine River basin is mainly released from urban activities (60–100%), especially in Paris and the downstream part of the basin. Contrastingly, in headwaters and/or tributaries with low urbanisation, the relative boron input to river from agricultural practices and rains increased, up to 10% and by 10 to 30%, respectively.

Multiconfiguration electromagnetic induction survey for paleochannel internal structure imaging: a case study in the alluvial plain of the River Seine, France

Abstract. The La Bassée floodplain area is a large groundwater reservoir controlling most of the water exchanged between local aquifers and hydrographic networks within the Seine River basin (France). Preferential flows depend essentially on the heterogeneity of alluvial plain infilling, whose characteristics are strongly influenced by the presence of mud plugs (paleomeander clayey infilling). These mud plugs strongly contrast with the coarse sand material that composes most of the alluvial plain, and can create permeability barriers to groundwater flows. A detailed knowledge of the global and internal geometry of such paleomeanders can thus lead to a comprehensive understanding of the long-term hydrogeological processes of the alluvial plain. A geophysical survey based on the use of electromagnetic induction was performed on a wide paleomeander, situated close to the city of Nogent-sur-Seine in France. In the present study we assess the advantages of combining several spatial offsets, together with both vertical and horizontal dipole orientations (six apparent conductivities), thereby mapping not only the spatial distribution of the paleomeander derived from lidar data but also its vertical extent and internal variability.

Caractérisation de l’industrie lithique de la fin du Néolithique, dans le bassin de la Seine (de la deuxième moitié du IVe millénaire à la fin du IIIe millénaire av. J.-C.)

Cet article présente une synthèse sur l’industrie lithique du Néolithique récent et final dans le bassin de la Seine (entre 3500 et 2100 avant notre ère). Son objectif est de distinguer l’industrie lithique du Néolithique récent de celle du Néolithique final et, plus largement, de préciser la définition des groupes culturels, leur localisation et leur chronologie par l’étude du mobilier lithique en contexte domestique et sépulcral. La première étape de la caractérisation porte sur les modalités de l’approvisionnement, généralement réalisé à proximité des occupations durant le Néolithique récent et final. L'importation de matières premières suit une même tendance, sur deux aspects, le sens de circulation des pièces en silex secondaire et tertiaire mais aussi la forme sous laquelle ces produits circulent. Le Néolithique final se distingue par une diffusion d’artefacts en roche verte et en silex du Turonien supérieur de la région du Grand-Pressigny. Au Néolithique récent, la production laminaire présente certaines caractéristiques au niveau du type de percussion utilisé (indirecte et directe tendre) mais aussi de la répartition géographique de ces techniques et sur le statut des produits laminaires en contexte sépulcral. Plusieurs indices suggèrent que le ralentissement de la production laminaire domestique débute à partir du Néolithique final. Cette période se distingue aussi par une diversification de l'outillage et par l’existence d’une production d’éclats par débitage centripète sur la façade maritime. L’étude comparative de plusieurs zones du bassin de la Seine met en évidence les variabilités temporelles et spatiales et interroge la validité des faciès régionaux (Augereau et al., 2007). L''existence d'un « faciès Marne » , proposé à l’issue de synthèses sur les pratiques funéraires, le mobilier en matière dure animale et la parure, est à nouveau validée par l''industrie lithique.

Agri-food-energy system metabolism: a historical study for northern France, from nineteenth to twenty-first centuries

We reconstruct the metabolism of cereal grain production and processing systems in the Seine river basin at four time points between 1860 and 2010 in terms of nitrogen and energy flows, on the basis of statistical data and modeling components. We integrate agricultural, nutrient and energy issues into a joint agri-food-energy system approach. Grain production and processing grew apart from a state of high local integration on the basis of local renewable energy and nitrogen sources to a state of national-scale energy and grain market integration. The grain production volume increased 6-fold under the effect of agricultural industrialization, while the local grain processing capacity dropped along with the decrease in local flour demand. Nitrogen use efficiency (NUE) increased from about 50% in the nineteenth century to about 66% today, and the fossil energy inputs to the system increased from 0.05 to 0.15 GJ/GJ of flour output. Nitrogen loss is today lower than in the early-twentieth century, but its embodied fossil energy content is five times higher, highlighting potential energy benefits from further NUE increase. The energy transition to fossil fuels marked the disruption of an agro-industrial regime founded on renewable energy self-provision and biological nitrogen fixation and helped mastering the system working conditions by reducing its intermittency.