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Développement d'une stratégie de localisation d'une source de contaminants en nappe : mesures innovantes et modélisation inverse

Abstract : Contaminated sites management and remediation can be complex and require a significant investment to locate the contaminant source, which delivers the higher pollutant mass fluxes. The study proposes a strategy for contaminant source localisation using in situ measurement and inverse modelling. First, an innovative tool was developed to measure groundwater velocity in a well. The developed tool called DVT (Direct Velocity Tool) made it possible to measure a low Darcy flux. Laboratory and field tests were performed with the DVT and compared to other velocity measurement tools. By combining the DVT with a local concentration measurement, it is possible to calculate the mass fluxes passing through wells. Then the thesis present the inverse modeling used for source localisation and parameters estimation. The study was done on two synthetics cases using the non-linear optimisation method. To adapt the method to a real management of polluted sites, an iterative strategy is developed by imposing a limited addition of new observations to each modeling phase. This strategy is base on the Data Worth approach. Source localisation results on the two synthetic cases made it possible to judge the method applicability to a real site problem. The source localisation strategy is then applied to a real site with (i) mass flux measurement with velocities (DVT) and concentrations and (ii) inverse modeling. The modeling phases made it possible to locate the new wells and helped the source localisation. Nevertheless, by analysing the results more precisely, the hydraulic conductivity field estimated by the optimisation did not correspond to reality. In addition, contaminant mass fluxes highlightes two distinct zones of flux. By analysing the pollutant ratio of the site, it appears that two plumes are potentially present. Thus, another inverse modeling phase has been tested (i) to locate the two potential sources and (ii) to estimate the chemistry of the site. Results of the strategy were compared to the geoprobe campaign which confirmed the second source location.
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Submitted on : Monday, May 13, 2019 - 10:42:14 AM
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  • HAL Id : tel-02127045, version 1

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Elyess Essouayed. Développement d'une stratégie de localisation d'une source de contaminants en nappe : mesures innovantes et modélisation inverse. Sciences de la Terre. Université Michel de Montaigne - Bordeaux III, 2019. Français. ⟨NNT : 2019BOR30006⟩. ⟨tel-02127045⟩

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