Greener Journal of Physical Sciences

Greener Journal of  Physical Sciences Vol. 2 (1), pp. 010-015, January, 2012.

ISSN: 2276-7851 © 2012 Greener Journals

Research Paper

Manuscript Number: GJPS11007

Evaluation of Subsoil Corrosivity Condition around a Sewage Pond using the Electrical Resistivity Method. A Case Study from the Basement Complex Terrain of Ile-Ife, Southwestern Nigeria.

*O.G. Bayowa and O.A. Adigun

 

Department of Earth Sciences, Ladoke Akintola University of Technology, PMB 4000 Ogbomoso, Nigeria.

*Corresponding Author Email: oyebayowa@ yahoo. com

Abstract:

Evaluation of subsoil corrosivity using the electrical resistivity method was carried out around a sewage pond in the Basement Complex terrain of Ile-Ife, Southwestern Nigeria with the aim of determining the subsoil geoelectric parameters (apparent resistivities) around the sewage pond at depth range of 0.5 m, 1.5 m and 3.0 m and to categorize the area into different corrosivity zones. The depths of investigation were selected based on the theoretical relationship (Z = 0.125AB) between depth of investigation Z (m) and the current electrode spacing (AB (m)) for Schlumberger Array. Twenty-five Vertical Electrical Sounding (VES) stations were occupied with ABEM SAS 1000 terrrameter along five N-S trending with maximum of 200 m long geophysical traverses. The station-station interval of 40 m was used to acquire apparent resistivities for electrode spacing (AB/2) of 2 m, 6 m and 12 m respectively which correspond to the selected depths theoretically; iso - resistivity maps were generated using Surfer 8 Software for each depth. The maps were qualitatively interpreted while three main subsoil corrosivity zones were delineated around the sewage pond. At depth 0.5 m, the western zone of the pond is underlain by slightly corrosive subsoil while other part is underlain by practically non-corrosive subsoil. At depth 1.5 m, the western part is characterized by both moderately corrosive subsoil and slightly corrosive subsoil while other part is characterized by practically non-corrosive subsoil. At 3.0 m depth, similar subsoil effect was observed. It can be concluded that the area around the sewage pond is underlain by moderately corrosive, slightly corrosive and practically non-corrosive subsoil. However, the degree of corrosivity around the pond increases westward with depth.
 
Key Words: Electrical Resistivity, Subsoil, Corrosivity, Sewage Pond, Ile-Ife, Nigeria.

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