Integrated Approach to Investigate the Effect of Leachate on Groundwater around the Ikot Ekpene Dumpsite in Akwa Ibom State, Southeastern Nigeria

Abstract

Geophysical, geochemical, and hydrogeological measurements have been integrated to assess the effect of leachate on groundwater quality within the dumpsite in Ikot Epene Local Government Area of Akwa Ibom State, Southern Nigeria, and its environs. The resistivity values and depth of burial of the geomaterials, constrained by geology, were used in producing resistivity cross sections which show the geoelectric distribution of the subsurface near and away from the dumpsite. The observed high conductivity in subsurface layers closed to the dumpsite is symptomatic of the leachate-loaded conductive fluid leached and drained into the subsurface. The hydrochemical results of some species conform to WHO standards, while some were found to be relatively higher due to dissolution, leaching, and draining of leachate related contaminants in the soil. The correlation indices of the ion pairs show no significant effect on the paired ions, indicating that the significant value of some of the individual ions is not geologic but due to precipitation from the leachate residue. In general, the effect of leachate is more dominant in the immediate groundwater pathway near the dumpsite than aquifer repositories away from it. The crossplots of the water resistivity and bulk resistivity show exponential increase for the different layers.

Geophysical Assessment of Vulnerability of Surficial Aquifer in the Oil Producing Localities and Riverine Areas in the Coastal Region of Akwa Ibom State, Southern Nigeria

“…The contamination of groundwater in these regions is also viewed to be due to salt water intrusion in marine water bodies that surround Eket and Onna local government areas. Although the geochemical data indicate elevation beyond the WHO standard for drinking water, indicating the possibility of saltwater-freshwater incursion within the layers below the protective cover in the region, the topographically low coastal zone is characterized by vadose zones that are drainable and susceptible to anthropogeically polluted matter based on longitudinal conductance that is less than 1 Siemens 16,19 . The IEC in Figure 6 shows that the gravity of protection in the oil cities is low on an average, with inhomogeneous protective layers that have windows for surface waste infiltration into the phreatic zones.…”

“…The results obtained from integration of the Schlumberger sounding, constrained by the nearby borehole and hydrochemical parameters of shallow lithology, provide a graphic detail of lithology of aquifer overburden materials that control the percolation of contaminant flow within the study area. The saltwater-freshwater incursion takes place within the phreatic zones, below the considered drainable vadose zone 19 . The resistivity distribution in the area gives an indication of inhomogeneous covering layer which overlies the phreatic zones.…”

“…The drainage in mapped area is made possible by the Kwa River, cross rivers and Etim Ekpo tributaries 17 . Studies conducted in the study area indicate that fine to gravelly sand within the depth range of 65-100 m serves as economic water repository [16][17][18][19] . The saltwater-freshwater incursion in the area takes place below the aquifer cover layer considered in this study 16 .…”

“…Vegetation in the study area is tropical rainforest type 18 . The noticeable wet and dry seasons are characterized by unstable amount of precipitation (230 to 390 mm monthly) and variation of temperature 19 . Table 1 gives the lithologic and stratigraphic correlation of hydrogeologic units of the study area.…”

Assessment of Economically Accessible Groundwater Reserve and Its Protective Capacity in Eastern Obolo Local Government Area of Akwa Ibom State, Nigeria, Using Electrical Resistivity Method

“…It comprises poorly sorted continental (fine, medium, and coarse) sands and gravels that alternate with lignite streaks, thin clay horizons, and lenses at some locations. The thin clay/shale horizons truncate the vertical and lateral extents of the sandy aquifers thereby building up multiaquifer systems in the area [17]. Thus both confined and partially confined aquifers can be found in the area.…”