Historique de l'origine des matières en suspension dans le Rhône (France) en utilisant la signature géochimique non-réactive des particules

International audienceSuspended particulate matter (SPM) conveyed by rivers contribute to the transport of numerous contaminants that can affect water quality through their desorption from particles or during diagenesis processes. In order to assess to SPM deliveries and associated contaminants to the Rhône River then to the Mediterranean Sea, it is essential to identify SPM sources at the scale of the whole Rhône watershed. We present a first study on the determination the historical SPM inputs from the tributaries in the Upper Rhône River. We apply an original geochemical mixing model onto two sediment cores collected in a same deposit area. To prevent chemical transformations which can occur during particles transport and after settlement of SPM, we use concentrations of key trace elements in the conservative fraction of SPM. Data acquired were integrated into a mixing model coupled to Monte Carlo simulation to assess uncertainties. In addition, the spatial heterogeneity was scrutinized using data from both sediment cores. To improve accuracy and precision of historical sediment source contributions, we compared mixing model data output using geochemical signatures of SPM from the various samples and from well characterizes flood events. Finally, historical sediment source contributions were compared to hydrological time series and SPM deliveries to the Rhone River

Historique de l'origine des matières en suspension dans le Rhône (France) en utilisant la signature géochimique non-réactive des particules

International audienceSuspended particulate matter (SPM) conveyed by rivers contribute to the transport of numerous contaminants that can affect water quality through their desorption from particles or during diagenesis processes. In order to assess to SPM deliveries and associated contaminants to the Rhône River then to the Mediterranean Sea, it is essential to identify SPM sources at the scale of the whole Rhône watershed. We present a first study on the determination the historical SPM inputs from the tributaries in the Upper Rhône River. We apply an original geochemical mixing model onto two sediment cores collected in a same deposit area. To prevent chemical transformations which can occur during particles transport and after settlement of SPM, we use concentrations of key trace elements in the conservative fraction of SPM. Data acquired were integrated into a mixing model coupled to Monte Carlo simulation to assess uncertainties. In addition, the spatial heterogeneity was scrutinized using data from both sediment cores. To improve accuracy and precision of historical sediment source contributions, we compared mixing model data output using geochemical signatures of SPM from the various samples and from well characterizes flood events. Finally, historical sediment source contributions were compared to hydrological time series and SPM deliveries to the Rhone River

Historique de l'origine des matières en suspension dans le Rhône (France) en utilisant la signature géochimique non-réactive des particules

International audienceSuspended particulate matter (SPM) conveyed by rivers contribute to the transport of numerous contaminants that can affect water quality through their desorption from particles or during diagenesis processes. In order to assess to SPM deliveries and associated contaminants to the Rhône River then to the Mediterranean Sea, it is essential to identify SPM sources at the scale of the whole Rhône watershed. We present a first study on the determination the historical SPM inputs from the tributaries in the Upper Rhône River. We apply an original geochemical mixing model onto two sediment cores collected in a same deposit area. To prevent chemical transformations which can occur during particles transport and after settlement of SPM, we use concentrations of key trace elements in the conservative fraction of SPM. Data acquired were integrated into a mixing model coupled to Monte Carlo simulation to assess uncertainties. In addition, the spatial heterogeneity was scrutinized using data from both sediment cores. To improve accuracy and precision of historical sediment source contributions, we compared mixing model data output using geochemical signatures of SPM from the various samples and from well characterizes flood events. Finally, historical sediment source contributions were compared to hydrological time series and SPM deliveries to the Rhone River

An updated review on tritium in the environment

International audienceVarious studies indicated more or less recently that organically bound tritium (OBT) formed from gaseous or liquid tritium releases into the environment potentially accumulates in organisms contradicting hypotheses associated to methods used to assess the biological impact of tritium on humans (ASN, 2010). Increasing research works were then performed during the last decade in order to gain knowledge on this radionuclide expected to be increasingly released by nuclear installations in the near future within the environment. This review focusses on publications of the last decade. New unpublished observations revealing the presence of technogenic tritium in a sedimentary archive collected in the upper reaches of the Rhône river and findings from the Northwestern Mediterranean revealing in all likelihood the impact of terrigenous tritium inputs on OBT levels recorded in living organisms are also presented. Identifying and understanding the physicochemical forms of tritium and the processes leading to its persistence in environmental compartments would explain most observations regarding OBT concentrations in organisms and definitively excludes that tritium would “bio accumulate” within living organisms. © 2017 Elsevier Lt

Distribution and geochemical behaviour of antimony in the Gironde Estuary A first qualitative approach to regional nuclear accident scenarios

International audienceAntimony (Sb) is a highly toxic trace element for which environmental biogeochemical cycles are still relatively poorly known, especially in coastal aquatic systems. In addition, Sb is a fission product in nuclear power plants (NPPs), presenting non-negligible decay and consecutive exposition rates over short to mean terms (i.e., 125Sb isotope half-life of 2.76 years). Understanding the environmental behaviour and fate of natural stable isotopes and combining this with intrinsic properties of the respective radionuclides (e.g. half-life) is essential to predict the environmental fate and potential dispersion of radioisotopes before accidental NPP events. In the present work, the distribution and geochemical behaviour of stable Sb are determined for the first time in the highly turbid Gironde Estuary. Both dissolved and particulate concentrations along the estuarine salinity and turbidity gradients were quantified during low, intermediate and high freshwater discharges. Results clearly suggest that long residence times within the salinity and turbidity gradients favour the observed non-conservative, additive behaviour of Sb. Distribution coefficients (log10 Kd ≈ 3.5–4.4 l kg− 1) indicate that in the Maximum Turbidity Zone (MTZ; SPM ~ 1000 mg l− 1) ~ 90% of total Sb occurs in the particulate phase, compared to only ~ 10% in the less turbid portions of the estuary (SPM ≤ 100 mg l− 1). We propose a first/broad qualitative approximation (scenarios) to possible behaviour and dispersion of Sb radionuclides in case of accidental release from the Blayais NPP located on the Gironde Estuary. Our results suggest that the hydrological situation and the position of the MTZ during a potential accident can be primordial to residence time and distribution pathways in the estuary. We estimate that (i) high river discharge and a downstream position of the MTZ may favour Sb radionuclide adsorption onto particles, implying long (months to years) residence times in the estuary and a high risk of seasonal upstream transport into the city of Bordeaux, whereas (ii) under low discharge conditions, dissolved Sb species will predominate implying rapid transport and higher dispersion along the coast. © 2016 Elsevier B.V

Origine et historique des apports de matières en suspension (MES) des affluents du Rhône : utilisation de la signature géochimique non-réactive des particules

International audienceSuspended particulate matter (SPM) flows in rivers are mainly due to soil erosion and anthropogenic activities. They contribute to the transport of a large amount of contaminants and can induce impacts on water quality and river ecosystem. To better manage these inputs in river systems, it is essential to identify the origin of sediments. In that way, SPM fluxes monitoring or fingerprinting approaches in rivers are increasingly addressed. In the frame of the Rhône sediment observatory (OSR) program, the Rhône River, which is the main sediment input to the Mediterranean Sea, is studied through several stations of measurement. Since 7 years, SPM were collected on the Rhône River and its tributaries for contrasting hydrological conditions allowing developing fingerprinting approaches. The aims of this study were to use major and trace element concentrations in the conservative fraction of SPM from the Rhône and its tributaries in order (i) to determine the actual relative contribution of SPM fluxes, with uncertainty, from tributaries to the Rhône River and (ii) to determine the historical SPM inputs of the tributaries by applying this approach on a sediment core. To determine the origin of sediment at given time and space, the use of conservative parameters is essential to avoid any tracer's transformations during particles transport. To assess element concentrations in the conservative fraction of SPM, samples were extracted by a total mineralization (HNO3, HCl, HF) and a soft extraction (HCl 1M). The discrimination of SPM and sediment sources were realized by using a Kruskal-Wallis test and a Discriminatory Factory Analysis to select element concentrations that could discriminate the main tributaries of the Rhône (Ain, Arve, Bourbre, Fier, Guiers, Saône, Isère, Durance). 17 discriminant elements were then integrated into a mixing model with uncertainty analysis using the Monte Carlo method. Our method allowed to correctly determining SPM origin in the Upper Rhône and downstream the confluence of the Rhône and Saône rivers, for contrasting hydrological conditions. These results were successfully confronted to SPM dynamics estimated by a hydro-sedimentary 1-D model or by using SPM and discharges data obtained via the OSR stations network. Determination of the SPM origin at the outlet of the Rhône is in progress in order to, first, integrate tributaries signatures from the downstream part of the Rhône and, second, to apply this method on a sediment core sampled at the outlet of the Rhône River. The results of the core analyses will allow defining a historical profile of sediment inputs at the outlet of the Rhône catchment

Origine et historique des apports de matières en suspension (MES) des affluents du Rhône : utilisation de la signature géochimique non-réactive des particules

International audienceSuspended particulate matter (SPM) flows in rivers are mainly due to soil erosion and anthropogenic activities. They contribute to the transport of a large amount of contaminants and can induce impacts on water quality and river ecosystem. To better manage these inputs in river systems, it is essential to identify the origin of sediments. In that way, SPM fluxes monitoring or fingerprinting approaches in rivers are increasingly addressed. In the frame of the Rhône sediment observatory (OSR) program, the Rhône River, which is the main sediment input to the Mediterranean Sea, is studied through several stations of measurement. Since 7 years, SPM were collected on the Rhône River and its tributaries for contrasting hydrological conditions allowing developing fingerprinting approaches. The aims of this study were to use major and trace element concentrations in the conservative fraction of SPM from the Rhône and its tributaries in order (i) to determine the actual relative contribution of SPM fluxes, with uncertainty, from tributaries to the Rhône River and (ii) to determine the historical SPM inputs of the tributaries by applying this approach on a sediment core. To determine the origin of sediment at given time and space, the use of conservative parameters is essential to avoid any tracer's transformations during particles transport. To assess element concentrations in the conservative fraction of SPM, samples were extracted by a total mineralization (HNO3, HCl, HF) and a soft extraction (HCl 1M). The discrimination of SPM and sediment sources were realized by using a Kruskal-Wallis test and a Discriminatory Factory Analysis to select element concentrations that could discriminate the main tributaries of the Rhône (Ain, Arve, Bourbre, Fier, Guiers, Saône, Isère, Durance). 17 discriminant elements were then integrated into a mixing model with uncertainty analysis using the Monte Carlo method. Our method allowed to correctly determining SPM origin in the Upper Rhône and downstream the confluence of the Rhône and Saône rivers, for contrasting hydrological conditions. These results were successfully confronted to SPM dynamics estimated by a hydro-sedimentary 1-D model or by using SPM and discharges data obtained via the OSR stations network. Determination of the SPM origin at the outlet of the Rhône is in progress in order to, first, integrate tributaries signatures from the downstream part of the Rhône and, second, to apply this method on a sediment core sampled at the outlet of the Rhône River. The results of the core analyses will allow defining a historical profile of sediment inputs at the outlet of the Rhône catchment

Behaviour of radiocaesium in coastal rivers of the Fukushima Prefecture (Japan) during conditions of low flow and low turbidity - Insight on the possible role of small particles and detrital organic compounds

International audienceTo investigate riverine transfers from contaminated soils of the Fukushima Prefecture in Japan to the marine environment, suspended sediments, filtered water, sediments and detrital organic macro debris deposited onto river beds were collected in November 2013 within small coastal rivers during conditions of low flow rates and low turbidity. River waters were directly filtered on the field and high efficiency well-type Ge detectors were used to analyse radiocaesium concentrations in very small quantities of suspended particles and filtered water (a few mg to a few g). For such base-flow conditions, our results show that the watersheds studied present similar hydro-sedimentary behaviours at their outlets and that the exports of dissolved and particulate radiocaesium are comparable. Moreover, the contribution of these rivers to the instantaneous export of radiocaesium to the ocean is similar to that of the Abukuma River. Our preliminary results indicate that, in the estuaries, radiocaesium concentrations in suspended sediments would be reduced by more than 80%, while radiocaesium concentration in filtered waters would be maintained. Significant correlations between radiocaesium concentrations and radiocaesium inventories in the soils of the catchments indicate that there was at that time little intra and inter-watershed variability in the transfer processes of radiocaesium from lands to rivers at this regional scale. The apparent liquid-solid partition coefficient (KD) values acquired for the lowest loads/finest particles complement the values acquired by using sediment traps and highlight the strong capacity of the smallest particles to transfer radiocaesium. Finally, but not least, our observations suggest that there could be a significant transfer of highly contaminated detrital biomass from forest litter to the downstream rivers in a rather conservative way. © 2015 Elsevier Ltd

K.: Improving cell phone awareness by using calendar information

Abstract. The many benefits that cell phones provide are at times overshadowed by the problems they create, as when one person’s cell phone disrupts a group activity, such as a class, meeting or movie. Cell phone interruption is only highlighted by the ever increasing number of mobile devices we carry. Many tools and techniques have been proposed in order to minimize interruption caused by mobile devices. In the current study, we use calendar information to infer users ’ activity and to automatically configure cell phones accordingly. Our in-situ experiment uses PDAs that run a cell phone simulator to examine the feasibility and design factors of such a solution. Our results show that both structured activities and appropriate cell phone configuration can be predicted with high accuracy using the calendar information. The results also show consistent mapping of activities to configuration for each individual. However there was a poor consistency of mapping activity to configuration across different participants. We discuss the results in relation to inaccuracy, spontaneous activities, and user reactions.