Abstract
The study tries to utilize vertical electrical sounding (VES) and 2D resistivity tomography to evaluate the region of influence of the leachate plume on the groundwater around a dumpsite at Onitsha expressway, southeastern Nigeria. The borehole log data were acquired and their respective geoposition logged with Garmin GPS device. In addition, four 1D (VES) soundings and 2D electrical profile data were acquired in the field utilizing the Schlumberger and Wenner profiles respectively. Petrozenith PZ-03 Resistivity meter was used to acquire the electrical data, while RES2DINV and WinResist software were used to interpret the 2D and 1D data respectively. The resulting geoelectic layers were correlated with the borehole logs and were interpreted according to their resistivity distribution. Results of the 2D inversion at profiles 1 and 3 showed low resistivity zones indicating influence from the leachate plume. Profiles 2 and 4 gave low resistivity zone within 14.6 and 44.3 Ωm from surface to between 0.375 and 3.60 m depths indicating influence from leachate plume. Likewise, profiles 1 and 3, which penetrated groundwater, also showed very low resistivity with resistivity ranging from 3.12 to 8.7 Ωm, from surface to few meters depths. This indicates that it has been polluted by the leachate. In contrast, Profiles 2 and 4, from the 2D inversion, has no leachate influence on the groundwater. The VES result showed that the depth to the water table at location 1, 2, 3 and 4 are 21.7 m, 17.9 m, 15.9 m and 12.2 m respectively, with the leachate plume flowing in the southeast direction in line with the groundwater flow direction.
Highlights
The study tries to utilize vertical electrical sounding (VES) and 2D resistivity tomography to evaluate the region of influence of the leachate plume on the groundwater around a dumpsite at Onitsha expressway, southeastern Nigeria
The electrical resistivity (ER) method has been chosen for this study over other geophysical methods because the target anomaly would more respond to electrical conductivity since the migrating leachate/contaminants are more conductive that the surrounding a rea[5]
Omolayo and T ope[9] examined the generation, migration and impact of the leachate plume on groundwater and the soil at Ibadan, southwestern Nigeria using 2D electrical imaging and element analysis, They concluded that the values of both the total dissolved solids and the nitrate were above the World Health Organization (WHO) standard, pose health risk to the inhabitants
Summary
The study tries to utilize vertical electrical sounding (VES) and 2D resistivity tomography to evaluate the region of influence of the leachate plume on the groundwater around a dumpsite at Onitsha expressway, southeastern Nigeria. He found that the groundwater in areas closest to the dumpsite, and up to 72 m away, are characterized by low resistivity values indicating influence of the contaminant He reported that a time lapse monitoring of the leachate plume shows that it spreads by 652 m2 per year. They stated that the result is in line with the chemical analysis of the samples taken from the area, where the contaminated areas had higher concentration of the chemical elements In their separate investigation, Omolayo and T ope[9] examined the generation, migration and impact of the leachate plume on groundwater and the soil at Ibadan, southwestern Nigeria using 2D electrical imaging and element analysis, They concluded that the values of both the total dissolved solids and the nitrate were above the WHO standard, pose health risk to the inhabitants. They reported that the flow path of the leachate is confined along the low resistivity zone close to the surface with no separate plume at the downstream
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