Faculty: Physical Sciences
Department: Applied Geophysics


Udoh, A. Christopher
Anakwuba E. K.
Onwuemesi A.G.


Resistivity and hydrogeochemical data were collected at three municipal solid waste-disposal sites in Uyo, Ikot Ekpene and Oron, Southeastern Nigeria, with the aim of investigating the impact of solid waste on the groundwater quality as a result of leachate accumulations. Fifty-two (52) vertical electrical soundings (VES) data were obtained using Schlumberger array with a maximum current electrode separation of 150m across the study area. The VES data were analysed with the aid of resistivity iteration and inversion software IPI2WIN. The results of qualitative interpretation reveal that the VES curves generated at Uyo and Oron dumpsites are typically H and K-curves, whereas at Ikot Ekpene, there are hybrid KH and AK-curves. The VES results in conjunction with the borehole logs showed mainly three to four lithologic layers namely; top lateritic sand, leachate contaminated sand, dry, fine to medium-grained sand, and medium to coarse-grained sand layers. It also revealed that the leachate contaminated layer has thickness range of 0.64 – 22.20m across the area and the resistivity values range from 4.06 – 20.00Ωm. The results show a wide range of resistivity variations ranging from 4.06Ωm to 45756.00Ωm reflecting the variation in origin of the materials in the dumpsites. The correlation of geo-electric cross sections shows a true variation of the different layers delineated throughout the study area. The computed layer parameters for the overburden and leachate of the interpreted VES data show that the values of various parameters range from low to high across Uyo and Oron areas: longitudinal conductance (0.20 – 2.00 mhom and 0.30 – 13.80 mhom); transverse resistance (5.00 to 185.00 m-ohm and 200.00 - 520.00 m-ohm); fractured contrast (0.0573 to 0.4157); and leachate thickness (2 to 56m). The area is characterized by a thick leachate zone, which is not favourable for good groundwater quality. The hydraulic conductivity of the area was deduced to vary between 6.19 and 24.70 m/day; while the transmissivity values range from 96.63 and 1351.18 m2/day. The hydrogeochemical analyses revealed that few water samples from boreholes surrounding the dumpsites exhibit elevated Total Dissolved Solids (TDS) and Cadmium, high electrical conductivity and reduced pH. The leachate migration paths within the study areas trend predominantly in NW-SE and NE-SW directions at Uyo and Oron respectively. The superimposition of leachate level with topography showed that the leachate level follows the topography. The vertical movement of leachate down to the groundwater level in Uyo dumpsite is relatively slow compared to that of Oron dumpsite. The result reveals intersecting pattern such that the static water level crisscrosses the leachate level surface at 35m in Oron area. This implies that the sink of the leachate level is beyond the groundwater level and this makes the groundwater unfit for the users. Based on all the results obtained, Oron dumpsite is the most contaminated.