Hydro-Geophysical Investigation of Contaminant Distribution at a Closed

This paper presents a hydro-geophysical investigation into the landfill leachate distribution and subsurface geology at a closed site in southwestern Ontario, Canada, using geophysical mapping and hydrological modeling approaches. Conductivity mapping was first conducted over the study site using a frequency-domain EM terrain conductivity meter, revealing an anomalous high-con-ductivity zone of about 200 m (S-N) × 80 m (W-E) at the western half of the site. The DC resistivity survey was then carried out at this anomalous zone with eight S-N profiles and three W-E profiles measuring 200m in length using a Wenner-α configuration. Our resistivity survey results indicate that the landfill leachate travels mainly south-east wards over the upper aquifer, with a minor vertical component into the upper weathered portion of the silt/sand aquitard at some locations. No contamination seems to exist in the lower sand aquifer. The geophysical results were later used to develop two conceptualized models for hydrological modeling. Our numerical results pre-dict the leachate distribution at the study site in the future, confirming that the contaminant will occupy the entire upper aquifer and the most of the aquitard in a time of 1000 years, and that the barrier of the aquitard will protect the lower sand aquifer from the leachate pollution. Thes