Investigation of Leachate Plume and Groundwater Pollution using Geophysical and Physio-chemical Methods in an Open Dumpsite at Idugosa, Federal Capital Territory (FCT), Abuja, Nigeria
A geophysical study has been carried out using the electrical resistivity method, Very LowFrequency Electromagnetic (VLF-EM) and physiochemical analysis to investigate the effects
of groundwater contamination in the vicinity of an open dumpsite at Idugosa. A Vertical
Electrical sounding was carried out at 100 m away from the dumpsite and the results revealed
an H-type curve with 3- layers, with a low resistivity value of 90.0 Ωm, thickness of 9.8 m and
depth of 11.3 m at the weathered basement. The control VES revealed 5 –layers of HK-type
curve. The resistivity of the weathered and fractured basement ranged from 241.8 Ωm to 2908.4
Ωm with a thickness range of 3.5 m to 13.6 m and a depth range of 5.6 m to 19.1 m. Results
of the horizontal profiling using Wenner profiling revealed a low resistivity value of 1.6 Ωm to
3.8 Ωm at a depth of 15 m to 30 m, concentrated at stations 20 to 100. The bottom of the western
part showed that the leachate plume had infiltrated and contaminated the groundwater in the
zone. The VLF-EM with the three profiles revealed high current density values on the KarousHjelt filter plot at distances of 20 m to 38 m for profile 1, 25 m to 50 m and 75 m to 95 m for
profile 2, revealing the presence of contaminants which is mainly from decayed organic matter
from waste bodies and heavy metals from the dumpsite. Profile 3 which is further away from
profile 1 revealed that the contamination is reduced as we move further away from the dumpsite
at about 10 m to 20 m, 50 m to 60 m and 90 m respectively. The physio-chemical analysis
results showed a pH range of 6.73 – 7.17 which is within the World Health Organization
(WHO) standard (6.5 - 8.5). The Electrical Conductivity (EC) value of the Idugosa dumpsite
was found to be 804.9 μS/cm, which is above the WHO standard for EC values, which should
not exceed 400 μS/cm. This high value can be attributed to the infiltration of the leachate plume
from the dumpsite. The EC for Idugosa control which is 188.0 μS/cm is within the WHO limit
for groundwater, thus its safe for consumption.