Characterization of a leachate contaminated site integrating geophysical and hydrogeological information

In this study we report the characterization of a leachate contaminated site, by following a methodology that integrates geophysical and geohydrological data to better constrain a hydrogeological model. The characterization of the site (subsurface structure, soil characteristics) included six seismic refraction profiles, three electromagnetic lines using transient domain electromagnetic soundings (TDEM), two electric resistivity tomography (ERT) profiles, five vertical electrical sounding (VES) and geohydrological testings and analysis to support the delimitation of the contaminant plume. The study area corresponds to the leachate lagoon of Oaxaca City landfill, southern Mexico. Its inferred hydrogeological model constitutes an example of the uselfuness of the integration of several diverse methods applied with the same objective, thus reducing the ambiguity of applying a single characterization technique. The results indicate that low resistivity values from 1.5 to 2.5 Ohm-m are related to a leachate polluted soil underlying the leachate lagoon and also associated with an anomaly enclosed in the rockbed. A displacement of the polluted plume to the SW from the lagoon was also detected. Water quality is quite good but the human activity in the study area confers a risk to the Zaachila aquifer.