Landfill leachate assessment by hydrological and geophysical data: case study NamSon, Hanoi, Vietnam

The main objective of this study was to assess the impact of the NamSon landfill on subsurface geological structure and hydrological environment by geophysical techniques and hydrochemical analysis of surface and groundwater. The electrical resistivity tomography (ERT), self-potential (SP) and very low frequency (VLF) methods were used for the investigation of geological structure near the landfill. Three profiles (900 m long in total) of the two-dimensional ERT, VLF density sections and 180 SP data points scattered throughout the study area near the disposal site constituted the basis of the data used in analysis. Additionally, surface water and groundwater samples were collected from six sites in the area for the chemical analysis. Interpretations of geophysical data show a low resistivity zone (< 15 Ωm), which appears to be a fully saturated zone with leachate from landfill. The results of the geophysical investigations are not always fully confirmed by the results of hydrochemical analysis. The quality of water in the vicinity of the landfill dramatically decreased over the year (2015–2016) and actions should be taken to inverse this negative trend.