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David Claval - One of the best experts on this subject based on the ideXlab platform.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of environmental radioactivity, 2020
    Co-Authors: Hugo Lepage, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhone River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhone River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Genissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations in SPM were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. These anomalous peaks could be explained by the heterogeneous spatial distribution of technogenic tritium leading to large variations of tritium concentrations within the samples even though collected in areas close to each other. The results highlight the need to investigate the amount of such technogenic tritium currently stored in the upstream Rhone River as it might be significant.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of Environmental Radioactivity, 2020
    Co-Authors: Lepage Hugo, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhône River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhône River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Génissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. Since similarly high OBT concentrations had already been observed in suspended and deposited sediments during normal flow condition, these anomalous peaks could be explained by the heterogeneous spatial distribution of OBT in sediment sources that were resuspended during the Flushing Operations. The results highlight the need to investigate the amount of OBT currently stored in the upstream Rhone River as it might be significant.

Hugo Lepage - One of the best experts on this subject based on the ideXlab platform.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of environmental radioactivity, 2020
    Co-Authors: Hugo Lepage, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhone River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhone River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Genissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations in SPM were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. These anomalous peaks could be explained by the heterogeneous spatial distribution of technogenic tritium leading to large variations of tritium concentrations within the samples even though collected in areas close to each other. The results highlight the need to investigate the amount of such technogenic tritium currently stored in the upstream Rhone River as it might be significant.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    'Elsevier BV', 2020
    Co-Authors: Hugo Lepage, Eyrolle Frédérique, Ducros Loic, Claval David
    Abstract:

    International audienceTritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhône River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhône River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Génissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. Since similarly high OBT concentrations had already been observed in suspended and deposited sediments during normal flow condition, these anomalous peaks could be explained by the heterogeneous spatial distribution of OBT in sediment sources that were resuspended during the Flushing Operations. The results highlight the need to investigate the amount of OBT currently stored in the upstream Rhone River as it might be significant

  • Impact of dam Flushing Operations on sediment dynamics and quality in the upper Rhône River, France.
    Journal of environmental management, 2019
    Co-Authors: Hugo Lepage, M. Launay, Hélène Angot, Jérôme Le Coz, Olivier Radakovitch, Cécile Miège, Stéphanie Gairoard, Marina Coquery
    Abstract:

    Abstract The Rhone River (France) has been used for energy production for decades and 21 dams have been built. To avoid problems due to sediment storage, dam Flushing Operations are periodically organized. The impacts of such Operations on suspended particulate matter (SPM) dynamics (resuspension and fluxes) and quality (physico-chemical characteristics and contamination), were investigated during a Flushing Operation performed in June 2012 on 3 major dams from the Upper Rhone River. The concentrations of major hydrophobic organic contaminants (polychlorinated biphenyls, polycyclic aromatic hydrocarbons - PAHs, bis(2-ethylhexyl)phthalate [DEHP] and 4-n-nonylphenol), trace metal elements, particulate organic carbon (POC) and particle size distribution were measured on SPM samples collected during this event as well as on those obtained from 2011 to 2016 at a permanent monitoring station (150 km downstream). This allows to compare the SPM and contaminant concentrations and fluxes during the 2012 dam Flushing Operations with those during flood events and baseflow regime. At equal water discharge, mean SPM concentrations during Flushing were on average 6–8 times higher than during flood events recorded from 2011 to 2016. While of short duration (19 days), the Flushing Operations led to the resuspension of SPM and contributed to a third of the mean annual SPM flux. The SPM contamination was generally lower during Flushing than during baseflow or flood, probably due to the fact that Flushing transports SPM only issued from resuspended sediment, with no autochtonous particles nor eroded soil. The only exception are PAHs and DEHP with higher concentrations during Flushing, which must be issued from the resuspension of legacy-contaminated sediments stored behind the dams before the implementation of emission regulations. During Flushing, the variations of POC and contaminant concentrations are also mostly driven by particle size. Finally, we propose a list of recommendations for the design of an adequate monitoring network to evaluate the impact of dam Flushing Operations on large river systems.

  • Consequences of a dam Flushing Operation on concentration and fluxes of suspended sediment and associated contaminants in the Rhône River
    European geosciences union general assembly, 2018
    Co-Authors: Hugo Lepage, Frédérique Eyrolle, M. Launay, Hélène Angot, Jérôme Le Coz, Marina Coquery, Olivier Radakovitch
    Abstract:

    The increasing need on energy and fluvial transport due to industrialization during the last century resulted in the construction of infrastructures along rivers, as dams or sluices. Thus, nineteen hydro-electrical dams were built along the Rhone River (France) since 1950. To improve the production of electricity and avoid problems due to sediment storage within these infrastructures, dam Flushing Operations are organized periodically. It has been demonstrated by numerous studies that several contaminants are strongly fixed to suspended particulate matters (SPM), especially the finest, and may be dispersed during Flushing Operations. Investigations were conducted in the upper Rhone River to evaluate the impact of dam Flushing Operations on suspended sediment and associated contaminants (metals, organic contaminants and radionuclides) concentrations and fluxes. The releases took about three weeks in June 2012, and almost fifty suspended sediment samples were collected at six stations along the upper Rhone River. Results demonstrated that suspended sediment concentration and flux were very high in the vicinity of the dam, but most of the sediments were stored in the upper part of the river. Thus, fluxes registered at other stations (approx. 100km downstream) were similar to those observed during flood events. For most of the contaminants (Polychlorobiphenyls-101 (PCB101), Cu, Hg . . . ), concentrations were lower during dam Flushing periods than during flood events or normal flow condition. This difference could be explained by particulate organic carbon (POC) concentrations that were also lower. Only Benzo[a]Pyrene had concentrations significantly higher (+ 50%). Spatial trend demonstrate an increase for all contaminants at the exception of PCB101 that remained constant with distance from upstream dams. Those variations may be related to POC, particle sizes, or additional source of contaminants such as industries or other tributaries. Finally, dam Flushing fluxes of contaminants were similar to flood-related fluxes and represent a non-negligible part of the annual fluxes. In 2012, 36% of the annual flux of sediments were transported during this Flushing event.

Gashin Shahsavari - One of the best experts on this subject based on the ideXlab platform.

  • A model for non-uniform sediment transport induced by Flushing in sewer channels.
    Water research, 2019
    Co-Authors: Alberto Campisano, Carlo Modica, Enrico Creaco, Gashin Shahsavari
    Abstract:

    A novel unsteady flow numerical model for the simulation of the transport of non-uniform non-cohesive sediment mixtures (SM) during Flushing Operation in sewers is presented in this paper. The model was applied to the case of a flush experimental test that was recently carried out in a combined sewer channel of the sewer system of Paris city that exhibits depositional problems due to relatively coarse sediments. The model output was compared to the results of the field experiments as well as to those obtained with a model for the transport of uniform sediments (US). The model for SM provided a reliable interpretation of the selective transport of the sediments deposited in the channel bed as induced by the flush. The comparison showed the model for SM to provide an enhanced description of the erosional effects of the flush on the deposits, including improved evaluation of the volume of sediments flushed out of the experimental channel in the field.

  • Experimental and numerical investigation of Flushing in combined sewer networks : case study of a Parisian trunk sewer
    2018
    Co-Authors: Gashin Shahsavari
    Abstract:

    Sediment accumulation on the invert of sewer channels has been recognized as one of the important sources of problems for the management of sewer networks.In the two most recent decades, Flushing has been put forward as one of the most common methods of sewer cleaning, to limit sediment accumulation especially in large trunk sewers.Sewer sediment transport processes are not fully understood yet, due to numerous unknown variables and difficult measuring conditions. The current research aimed firstly to setup a field experimental campaign to obtain high-quality data. This data allowed understanding of the processes associated with Flushing Operation in sewers. In addition, this study aimed to model the Flushing processes properly in order to set-up an adequate and practical numerical tool able to predict sediment removal of Flushing in the sewer network of Paris. To this purpose, two models were used: (i) a simple model for uniform sediment transport, which is the most common used approach; and (ii) a more complex model for non-uniform sediment transport of mixtures. A comparative analysis was carried out to highlight advantages and drawbacks of either. Overall, the results pointed out that the numerical modelling is able to reproduce faithfully hydrodynamics and sediment transport during Flushing Operations. In fact, both models enabled evaluation of flush behaviour and associated sediment transport. However, despite its higher complexity and computational burden, the latter model provides better insight into the prediction of the removal effectiveness of flushes

  • Experimental and Numerical investigation of Flushing in Combined sewer Networks – Case study of a Parisian Trunk Sewer
    2018
    Co-Authors: Gashin Shahsavari
    Abstract:

    Sediment accumulation on the invert of sewer channels has been recognized as one of the important sources of problems for the management of sewer networks. In the two most recent decades, Flushing has been put forward as one of the most common methods of sewer cleaning, to limit sediment accumulation especially in large trunk sewers. Sewer sediment transport processes are not fully understood yet, due to numerous unknown variables and difficult measuring conditions. The current research aimed firstly to setup a field experimental campaign to obtain high-quality data. This data allowed understanding of the processes associated with Flushing Operation in sewers. In addition, this study aimed to model the Flushing processes properly in order to set-up an adequate and practical numerical tool able to predict sediment removal of Flushing in the sewer network of Paris. To this purpose, two models were used: (i) a simple model for uniform sediment transport, which is the most common used approach; and (ii) a more complex model for non-uniform sediment transport of mixtures. A comparative analysis was carried out to highlight advantages and drawbacks of either. Overall, the results pointed out that the numerical modelling is able to reproduce faithfully hydrodynamics and sediment transport during Flushing Operations. In fact, both models enabled evaluation of flush behaviour and associated sediment transport. However, despite its higher complexity and computational burden, the latter model provides better insight into the prediction of the removal effectiveness of flushes.

  • Validation of an unsteady flow numerical model for sediment transport induced by Flushing Operation in combined sewers
    2018
    Co-Authors: Gashin Shahsavari, Carlo Modica, Alberto Campisano, Gilles Arnaud-fassetta
    Abstract:

    An unsteady flow numerical model based on the solution of the 1-D De Saint Venant-Exner equations was developed and validated against the results of a field Flushing experiment that was carried out in the year 2014 within a combined sewer trunk of the Paris sewer system. The comparison of numerical and experimental results showed that the model may reproduce in a proper way the erosional effects of the flush on the mobile bed of the sewer at the end of the experiment. Model results confirmed the potential erosive effect of the flush up to several hundreds meters downstream of the Flushing device, with a significant reduction of the deposited sediments in the channel.

  • Preliminary analysis of turbidity measurements during a Flushing Operation in combined sewer channel
    2016
    Co-Authors: Gashin Shahsavari, Gilles Arnaud-fassetta, Roberto Bertilotti, Hossein Bonakdari, Isa Ebtehaj, Hamid Moeeni, Carlo Modica, Alberto Campisano
    Abstract:

    Flow turbidity at different elevations was continuously monitored in five cross-sections of a real combined-sewer channel stretch during a flush experiment. The preliminary analysis of the collected turbidity data in terms of quality and spatial variability of the time series is presented in this paper. Also, an Autoregressive Moving Average (ARMA) model was setup to evaluate potential prediction of turbidity values showing a good estimation performance with relatively small errors.

Frédérique Eyrolle - One of the best experts on this subject based on the ideXlab platform.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of environmental radioactivity, 2020
    Co-Authors: Hugo Lepage, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhone River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhone River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Genissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations in SPM were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. These anomalous peaks could be explained by the heterogeneous spatial distribution of technogenic tritium leading to large variations of tritium concentrations within the samples even though collected in areas close to each other. The results highlight the need to investigate the amount of such technogenic tritium currently stored in the upstream Rhone River as it might be significant.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of Environmental Radioactivity, 2020
    Co-Authors: Lepage Hugo, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhône River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhône River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Génissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. Since similarly high OBT concentrations had already been observed in suspended and deposited sediments during normal flow condition, these anomalous peaks could be explained by the heterogeneous spatial distribution of OBT in sediment sources that were resuspended during the Flushing Operations. The results highlight the need to investigate the amount of OBT currently stored in the upstream Rhone River as it might be significant.

  • Consequences of a dam Flushing Operation on concentration and fluxes of suspended sediment and associated contaminants in the Rhône River
    European geosciences union general assembly, 2018
    Co-Authors: Hugo Lepage, Frédérique Eyrolle, M. Launay, Hélène Angot, Jérôme Le Coz, Marina Coquery, Olivier Radakovitch
    Abstract:

    The increasing need on energy and fluvial transport due to industrialization during the last century resulted in the construction of infrastructures along rivers, as dams or sluices. Thus, nineteen hydro-electrical dams were built along the Rhone River (France) since 1950. To improve the production of electricity and avoid problems due to sediment storage within these infrastructures, dam Flushing Operations are organized periodically. It has been demonstrated by numerous studies that several contaminants are strongly fixed to suspended particulate matters (SPM), especially the finest, and may be dispersed during Flushing Operations. Investigations were conducted in the upper Rhone River to evaluate the impact of dam Flushing Operations on suspended sediment and associated contaminants (metals, organic contaminants and radionuclides) concentrations and fluxes. The releases took about three weeks in June 2012, and almost fifty suspended sediment samples were collected at six stations along the upper Rhone River. Results demonstrated that suspended sediment concentration and flux were very high in the vicinity of the dam, but most of the sediments were stored in the upper part of the river. Thus, fluxes registered at other stations (approx. 100km downstream) were similar to those observed during flood events. For most of the contaminants (Polychlorobiphenyls-101 (PCB101), Cu, Hg . . . ), concentrations were lower during dam Flushing periods than during flood events or normal flow condition. This difference could be explained by particulate organic carbon (POC) concentrations that were also lower. Only Benzo[a]Pyrene had concentrations significantly higher (+ 50%). Spatial trend demonstrate an increase for all contaminants at the exception of PCB101 that remained constant with distance from upstream dams. Those variations may be related to POC, particle sizes, or additional source of contaminants such as industries or other tributaries. Finally, dam Flushing fluxes of contaminants were similar to flood-related fluxes and represent a non-negligible part of the annual fluxes. In 2012, 36% of the annual flux of sediments were transported during this Flushing event.

Loïc Ducros - One of the best experts on this subject based on the ideXlab platform.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of environmental radioactivity, 2020
    Co-Authors: Hugo Lepage, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhone River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhone River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Genissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations in SPM were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. These anomalous peaks could be explained by the heterogeneous spatial distribution of technogenic tritium leading to large variations of tritium concentrations within the samples even though collected in areas close to each other. The results highlight the need to investigate the amount of such technogenic tritium currently stored in the upstream Rhone River as it might be significant.

  • Spatial and temporal variation of tritium concentrations during a dam Flushing Operation
    Journal of Environmental Radioactivity, 2020
    Co-Authors: Lepage Hugo, Frédérique Eyrolle, Loïc Ducros, David Claval
    Abstract:

    Tritium is a radionuclide commonly observed worldwide in riverine systems. In the Rhône River downstream the Lake Geneva (Switzerland and France), its occurrence is also related to its use for its luminescent properties in watchmaking paints. In fact, tritium is regularly observed at anomalous levels in this river and extreme events such as Flushing Operations might conduct to its transport downstream. In the Rhône River, characterized by 21 dams downstream the Geneva Lake, such Operations are regularly organized to remove the sediments and limit problematic consequences such as siltation and increased flooding hazards. The consequences of dam Flushing Operations on tritium concentrations were thus investigated. Samples of Suspended Particulate Matter (SPM) and water were collected in the Rhone River downstream of Geneva in June 2012, during a planned Flushing Operation of three upstream reservoirs (Verbois, Chancy-Pougny and Génissiat). The concentrations of tritiated water (HTO) and organically bound Tritium (OBT) were measured and compared to reference concentrations. The Flushing Operations had no impact on the HTO concentration while the increases observed were related to the authorized releases of HTO from a nuclear power plant located downstream the dams. High increases of OBT concentrations were observed at two stations (Creys-Malville and Jons) without clear spatial or temporal trends. Since similarly high OBT concentrations had already been observed in suspended and deposited sediments during normal flow condition, these anomalous peaks could be explained by the heterogeneous spatial distribution of OBT in sediment sources that were resuspended during the Flushing Operations. The results highlight the need to investigate the amount of OBT currently stored in the upstream Rhone River as it might be significant.