Groundwater contamination in the basement-complex area of Ile-Ife, southwestern Nigeria: A case study using the electrical-resistivity geophysical method |
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| Authors: | A Adepelumi B Ako T Ajayi |
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| Institution: | Geophysics Department, Observatorio Nacional-CNPq, Rua Gal. Jose Cristino 77, CEP 20921-400, S?o Cristov?o, Rio de Janeiro, Brazil,
Geology Department, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria,
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| Abstract: | Hydrogeoenvironmental studies were carried out at the sewage-disposal site of Obafemi Awolowo University campus, Ile-Ife,
Nigeria. The objective of the survey was to determine the reliability of the electrical-resistivity method in mapping pollution
plumes in a bedrock environment. Fifty stations were occupied with the ABEM SAS 300C Terrameter using the Wenner array. The
electrical-resistivity data were interpreted by a computer-iteration technique. Water samples were collected at a depth of
5.0 m in 20 test pits and analyzed for quality. The concentrations of Cr, Cd, Pb, Zn, and Cu are moderately above the World
Health Organization recommended guidelines. Plumes of contaminated water issuing from the sewage ponds were delineated. The
geoelectric sections reveal four subsurface layers, with increasing depth, lateritic clay, clayey sand/sand, and weathered/fractured
bedrock, and fresh bedrock. The deepest layers, 3 and 4, constitute the main aquifer, which has a thickness of 3.1–67.1 m.
The distribution of the elements in the sewage effluent confirms a hydrological communication between the disposal ponds and
groundwater. The groundwater is contaminated, as shown by sampling and the geophysical results. Thus, the results demonstrate
the reliability of the direct-current electrical-resistivity geophysical method in sensing and mapping pollution plumes in
a crystalline bedrock environment.
Electronic Publication |
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| Keywords: | Contamination Geophysical methods Hydrochemistry Nigeria Waste disposal |
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