Geophysical Contribution for the Mapping the Contaminant Plume of Leachate from Rubbish Dumpsite of Hevie, Benin

In majority of the countries in the process of development like the Benin, the presence of dumpsite of rubbish can cause pollution of the groundwater. Indeed, the leachate resulting from the seepage of rain water into rubbish can infiltrate and pollute the water table. The evaluation of the infiltration of the leachate was carried out by the geophysical methods of frequential electromagnetism in EM34 and Electrical Resistivity Tomography (ERT). The electromagnetic map circumscribed the lateral limits of the leachate diffusion and the electromagnetic surveys showed that it infiltrated with a depth of 20m. The two cross sections of electrical resistivity tomography of NS and SW-NE direction made it possible to map the plume of leachate. These results show that the contact water table - leachate is rather discontinuous, the depths of the feather of leachate varying from few meters to 22m for an average static level of 18m. The leachate infiltration occurs with variable depths and is not everywhere in contact with the water table. This discontinuous pollution has been observed in the water quality of the wells. Indeed, the analyses of water samples of the wells showed a great variation of heavy metal pollution in rather close wells