Marine radioecology after the Fukushima Dai-ichi nuclear accident : are we better positioned to understand the impact of radionuclides in marine ecosystems?

© The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Science of The Total Environment 618 (2017): 80-92, doi:10.1016/j.scitotenv.2017.11.005.This paper focuses on how a community of researchers under the COMET (CO-ordination and iMplementation of a pan European projecT for radioecology) project has improved the capacity of marine radioecology to understand at the process level the behaviour of radionuclides in the marine environment, uptake by organisms and the resulting doses after the Fukushima Dai-ichi nuclear accident occurred in 2011. We present new radioecological understanding of the processes involved, such as the interaction of waterborne radionuclides with suspended particles and sediments or the biological uptake and turnover of radionuclides, which have been better quantified and mathematically described. We demonstrate that biokinetic models can better represent radionuclide transfer to biota in non-equilibrium situations, bringing more realism to predictions, especially when combining physical, chemical and biological interactions that occur in such an open and dynamic environment as the ocean. As a result, we are readier now than we were before the FDNPP accident in terms of having models that can be applied to dynamic situations. The paper concludes with our vision for marine radioecology as a fundamental research discipline and we present a strategy for our discipline at the European and international levels. The lessons learned are presented along with their possible applicability to assess/reduce the environmental consequences of future accidents to the marine environment and guidance for future research, as well as to assure sustainability of marine radioecology in Europe and globally. This guidance necessarily reflects on why and where further research funding is needed, signalling the way for future investigations.The research leading to this paper has received funding from the European Union's seventh Framework programme (FP7/2007-2013) under grant agreement No. is 604974 (Projects within COMET: Marine Initial Research Activity and The impact of recent releases from the Fukushima nucleaR Accident on the Marine Environment - FRAME). Sampling off Japan has been supported by the Gordon and Betty Moore Foundation, the Deerbrook Charitable Trust and contributions to the WHOI Centre for Marine and Environmental Radioactivity. We acknowledge the JSPS KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas Grant No. 24110005 for supporting in part the activities during the research cruises to the FDNPP area

A review on cesium desorption at the freshwater-seawater interface

International audienceUnderstanding the processes governing the behavior of radiocesium in the sea is still essential to make accurate assessments of its potential impacts on marine ecosystems. One of the most important of this process is the desorption that may occur at the river-sea interface due to changes in physico-chemical conditions, including ionic strength and solution composition. It has been the object of many studies using various kinds of field measurements or laboratory experiments, but there was no global interpretation of these works and their results. The present review summarizes relevant laboratory experiments studying desorption of Cs (stable or radioactive) from particles in sea or brackish waters.To date, 32 experimental studies have been carried out on 68 Cs-bearing samples since 1964. A wide range of desorbed fraction (0-86%) is observed, partly depending on the experimental design. For particles containing radiocesium issued from a contamination in the environment, the desorption ranges from 0 to 64% of the particulate activity, with a median at only 3%. Particles contaminated in laboratory show a range between 6 and 86% with a multimodal distribution. The desorption initiates at low salinity (3-4) and rapidly reaches a threshold around 10-15. Laboratory experiments show that two first-order reactions govern the kinetics of the process, with half-life reaction times of one hour and a few days. These two reactions are probably linked to the adsorption of Cs onto different particles sites. Also, the dynamic of Cs desorption depends on its initial distribution on these different sites, in relation with the history of its contamination and an aging effect

A fuzzy classification of the hydrodynamic forcings of the Rhone River plume: an application in case of accidental release of radionuclides

International audienceAssessing and modelling the coastal plume dispersion of nuclearized rivers is strategic in case of accidental releases for the protection of vulnerable areas, but taking into account all the possible hydrodynamical conditions is challenging. River plumes are mostly affected by wind and river discharge, but the variability of these two forcings suggest that data mining methods may be particularly effective to define their major trends and influences on the plume behavior.This study uses fuzzy c-mean clustering on Rhone River (France) discharge and wind speed at its estuary for two objectives: explaining the variability of the riverplume by defining scenarios of hydrodynamic forcings, and relating these scenarios with the spatial extension of the plume . The application to the Rhone River, the most nuclearized European river, highlighted the ability of this method to classify a 10 years serie of wind and discharge into 6 scenarios with remarkable characteristics. These scenarios correspond to different surface currents and plume behaviors, and they were used to simulate the extension and dilution of a radioactive release. These simulations can be used as a quick decision tool, and a decisional tree is also proposed to identify in real time which climatological scenario occurs at the river mouth and the potential plume pattern

A fuzzy classification of the hydrodynamic forcings of the Rhone River plume: an application in case of accidental release of radionuclides

Assessing and modelling the coastal plume dispersion of nuclearized rivers is strategic in case of accidental releases, but taking into account the variation of main hydrodynamic forcings is challenging. This study uses fuzzy c-mean clustering of a 10 years series of discharge and wind speed at the Rhone River estuary (France) in order to explain the variability of its plume. The method allows to classify the data into 6 scenarios of hydrodynamic forcings that were related to different spatial extensions of the plume, as well as to surface currents measured in-situ. These scenarios were used to simulate the extension and dilution of a radioactive release issued from the river. Based on threshold values of the forcings, a decisional tree is proposed to provide a quick decision tool identifying, in real time, which climatological scenario occurs at the river mouth and the potential plume pattern

Transfert particulaire-dissous des radioisotopes à l’embouchure

Ce livrable présente les travaux réalisés sur le mécanisme de désorption des radionucléides à l’embouchure du Rhône et les campagnes de terrain estivales destinées à évaluer l’étendue du coin salé. Certains éléments traces métalliques fixés sur des particules fluviales peuvent passer en phase dissoute lorsqu’ils arrivent en mer sous l’effet d’une désorption. Leur devenir en Méditerranée devient alors différent, et ceci peut avoir des conséquences en termes d’évaluation du risque et pour le cas de rejets accidentels dans le fleuve. L’étude s’est focalisée sur le comportement du Césium-137 dans cette zone, un élément radioactif associé aux installations nucléaires. Les objectifs étaient d’évaluer si cet élément est effectivement désorbé à son arrivée en milieu salé, l’interface eau douce-eau salé pouvant se produire en mer ou à l’intérieur des terres. Ce dernier cas étant un des plus impactant, la structuration du coin salé lorsqu’il pénètre dans le Rhône a été étudiée pour définir ses caractéristiques. Le 137Cs peut se désorber à partir d’une salinité de 3 à 4 g/l. Les activités actuelles dans le Rhône sont très faibles et ne permettent pas de mettre en évidence ce phénomène in-situ, mais les développements méthodologiques réalisés permettront désormais de faire ces mesures à tout moment en cas de besoin (rejets accidentels). La stratification du coin salé dans le fleuve se met en place dès que les débits tombent en dessous de 1500-1200 m3/s. Les techniques de mesure (ADCP, CTD) permettent d’avoir une très bonne représentation de ces structures dans l’espace, qui montrent une stratification extrêmement marquée. La remontée dans les terres est fortement corrélée au débit moyen sur les 5 jours précédents. Ces données sont et seront utilisées pour réaliser la modélisation hydrologique de cette interface dans l’OSR 6

Transfert particulaire-dissous des radioisotopes à l’embouchure

Ce livrable présente les travaux réalisés sur le mécanisme de désorption des radionucléides à l’embouchure du Rhône et les campagnes de terrain estivales destinées à évaluer l’étendue du coin salé. Certains éléments traces métalliques fixés sur des particules fluviales peuvent passer en phase dissoute lorsqu’ils arrivent en mer sous l’effet d’une désorption. Leur devenir en Méditerranée devient alors différent, et ceci peut avoir des conséquences en termes d’évaluation du risque et pour le cas de rejets accidentels dans le fleuve. L’étude s’est focalisée sur le comportement du Césium-137 dans cette zone, un élément radioactif associé aux installations nucléaires. Les objectifs étaient d’évaluer si cet élément est effectivement désorbé à son arrivée en milieu salé, l’interface eau douce-eau salé pouvant se produire en mer ou à l’intérieur des terres. Ce dernier cas étant un des plus impactant, la structuration du coin salé lorsqu’il pénètre dans le Rhône a été étudiée pour définir ses caractéristiques. Le 137Cs peut se désorber à partir d’une salinité de 3 à 4 g/l. Les activités actuelles dans le Rhône sont très faibles et ne permettent pas de mettre en évidence ce phénomène in-situ, mais les développements méthodologiques réalisés permettront désormais de faire ces mesures à tout moment en cas de besoin (rejets accidentels). La stratification du coin salé dans le fleuve se met en place dès que les débits tombent en dessous de 1500-1200 m3/s. Les techniques de mesure (ADCP, CTD) permettent d’avoir une très bonne représentation de ces structures dans l’espace, qui montrent une stratification extrêmement marquée. La remontée dans les terres est fortement corrélée au débit moyen sur les 5 jours précédents. Ces données sont et seront utilisées pour réaliser la modélisation hydrologique de cette interface dans l’OSR 6

Modelling the transfer of 137Cs along a river-sea continuum and application to accidental release scenarios

International audienceNumerical models allowing to simulate the transfer of radionuclides over long distance in the environment must take into account the relevant interfaces where bio-physico-chemical processes may modify the fluxes exchanged between compartments. Estuaries are one of such hot spot area, since they may trap contaminated particles or release radionuclides from these particles through desorption. A box-model has been developed and applied to the Rhone River estuary (France) with field data in order to couple a river (Casteaur) and a sea dispersion model (Sterne) for simulating the transfer of 137Cs along this continuum. This model, also suitable for other estuaries, allows to estimate the hydrodynamic conditions acting at the mouth (saltwedge into the estuary vs external plume on sea) and the freshwater/seawater mixing. It focuses on dissolved 137Cs and take into account the possible desorption from particles, which is described in the estuary box-model with kinetic rates calibrated from adsorption/desorption experiment in laboratory. This experiment was designed to specifically study the influence of salinity and of the ageing effect. They particularly showed that desorption occurred above a salinity of 3 to 4, and that its importance increased inversely with the duration of the adsorption phase (ageing effect). Such river-sea continuum modelling can be used to anticipate the dispersion of a 137Cs release in case of accident from one of the nuclear installations along the river. For this a statistical approach through fuzzy c-mean clustering of a 10 years series of river discharge and wind speed collected at the estuary was set up to explain the variability of the surface plume. The method allows to define 6 scenarios corresponding to the most usual occurrence of these two hydrodynamic forcing, which were used to simulate the extension and dilution of a release fixed at 1Tbq over a temporal window of 48 h.Finally, databases reporting biophysical and socio-economic environments for this area were collected and used to define sensitivity indicators. They were associated to 5 classes of vulnerability relatively to the impact of a radioactive contamination, and aggregated to constitute a final sensitivity basemap. This map was confronted to the simulations of 137Cs release under the 6 hydroclimatic scenarios, for which the seawater activities were converted into fish activities and separated into 4 classes partly based on regulatory limits for food contamination. This work is in relation with the challenge 1 of the ALLIANCE SRA: predict human and wildlife exposure in a robust way by quantifying key processes that influence radionuclide transfers and exposure

Modelling the transfer of 137Cs along a river-sea continuum and application to accidental release scenarios

International audienceNumerical models allowing to simulate the transfer of radionuclides over long distance in the environment must take into account the relevant interfaces where bio-physico-chemical processes may modify the fluxes exchanged between compartments. Estuaries are one of such hot spot area, since they may trap contaminated particles or release radionuclides from these particles through desorption. A box-model has been developed and applied to the Rhone River estuary (France) with field data in order to couple a river (Casteaur) and a sea dispersion model (Sterne) for simulating the transfer of 137Cs along this continuum. This model, also suitable for other estuaries, allows to estimate the hydrodynamic conditions acting at the mouth (saltwedge into the estuary vs external plume on sea) and the freshwater/seawater mixing. It focuses on dissolved 137Cs and take into account the possible desorption from particles, which is described in the estuary box-model with kinetic rates calibrated from adsorption/desorption experiment in laboratory. This experiment was designed to specifically study the influence of salinity and of the ageing effect. They particularly showed that desorption occurred above a salinity of 3 to 4, and that its importance increased inversely with the duration of the adsorption phase (ageing effect). Such river-sea continuum modelling can be used to anticipate the dispersion of a 137Cs release in case of accident from one of the nuclear installations along the river. For this a statistical approach through fuzzy c-mean clustering of a 10 years series of river discharge and wind speed collected at the estuary was set up to explain the variability of the surface plume. The method allows to define 6 scenarios corresponding to the most usual occurrence of these two hydrodynamic forcing, which were used to simulate the extension and dilution of a release fixed at 1Tbq over a temporal window of 48 h.Finally, databases reporting biophysical and socio-economic environments for this area were collected and used to define sensitivity indicators. They were associated to 5 classes of vulnerability relatively to the impact of a radioactive contamination, and aggregated to constitute a final sensitivity basemap. This map was confronted to the simulations of 137Cs release under the 6 hydroclimatic scenarios, for which the seawater activities were converted into fish activities and separated into 4 classes partly based on regulatory limits for food contamination. This work is in relation with the challenge 1 of the ALLIANCE SRA: predict human and wildlife exposure in a robust way by quantifying key processes that influence radionuclide transfers and exposure

Modelling the transfer of 137Cs along a river-sea continuum and application to accidental release scenarios

International audienceNumerical models allowing to simulate the transfer of radionuclides over long distance in the environment must take into account the relevant interfaces where bio-physico-chemical processes may modify the fluxes exchanged between compartments. Estuaries are one of such hot spot area, since they may trap contaminated particles or release radionuclides from these particles through desorption. A box-model has been developed and applied to the Rhone River estuary (France) with field data in order to couple a river (Casteaur) and a sea dispersion model (Sterne) for simulating the transfer of 137Cs along this continuum. This model, also suitable for other estuaries, allows to estimate the hydrodynamic conditions acting at the mouth (saltwedge into the estuary vs external plume on sea) and the freshwater/seawater mixing. It focuses on dissolved 137Cs and take into account the possible desorption from particles, which is described in the estuary box-model with kinetic rates calibrated from adsorption/desorption experiment in laboratory. This experiment was designed to specifically study the influence of salinity and of the ageing effect. They particularly showed that desorption occurred above a salinity of 3 to 4, and that its importance increased inversely with the duration of the adsorption phase (ageing effect). Such river-sea continuum modelling can be used to anticipate the dispersion of a 137Cs release in case of accident from one of the nuclear installations along the river. For this a statistical approach through fuzzy c-mean clustering of a 10 years series of river discharge and wind speed collected at the estuary was set up to explain the variability of the surface plume. The method allows to define 6 scenarios corresponding to the most usual occurrence of these two hydrodynamic forcing, which were used to simulate the extension and dilution of a release fixed at 1Tbq over a temporal window of 48 h.Finally, databases reporting biophysical and socio-economic environments for this area were collected and used to define sensitivity indicators. They were associated to 5 classes of vulnerability relatively to the impact of a radioactive contamination, and aggregated to constitute a final sensitivity basemap. This map was confronted to the simulations of 137Cs release under the 6 hydroclimatic scenarios, for which the seawater activities were converted into fish activities and separated into 4 classes partly based on regulatory limits for food contamination. This work is in relation with the challenge 1 of the ALLIANCE SRA: predict human and wildlife exposure in a robust way by quantifying key processes that influence radionuclide transfers and exposure