Understanding leachate transport in a variably saturated zone using ERT and process based modeling

Understanding spatio-temporal variation of solute distribution in subsurface is a challenging assignment, in particular, when there is only limited number of observation wells in the area of interest. In this study, in order to overcome the spatial limitation of monitoring observation wells, electrical resistivity tomography (ERT) of subsurface is measured over a period of time and solute distribution is inferred from those ERT results. ERT has been performed several times between March 2011 and February 2012 to observe leachate transport from a livestock mortalities burial in a rural area of Korea. Groundwater had been sampled in an observation well near the burial. A process based model describing flow and transport in a variably saturated zone has been built to represent the burial site of this study. The ERT results show abnormal resistivity zones which are supposed as leachate leakage from the burial. The results of sampling, modeling and ERT are used in combination to obtain quantitative analysis of leachate distribution. Electrical conductivity was converted to concentration using a function relating the solute content in the groundwater sample with the corresponding electrical conductivity. Under a limited knowledge of subsurface characteristics and unfavorable sampling conditions, the method provided improved insight in leachate distribution of the study site.