World Journal of Innovative Research (WJIR) ISSN: 2454-8236, Volume-6, Issue-5, May 2019 Pages 22-29 22 www.wjir.org Abstract— Geo-tomography study has been undertaken to determine the level of pollution occasioned by hydrocarbon spill at Ijedodo section of petroleum pipeline route at Ijedodo area of Abule Ado, Lagos. The field study involved the electrical resistivity tomography method using Dipole-Dipole electrode configuration. Traverse length of 1,870 m was occupied with electrode separations of 10 m and inter-dipole separation factor (n) varied from 1 to 8. The study area is underlain by the Dahomey Sedimentary Basin. The data are presented as field and theoretical pseudosections alongside 2-D resistivity structure. 2-D Resistivity Structure output presents inversion of the field data to obtain a model utilized for subsurface characterization. Observed high resistivity values are attributable to resistive sand units while low values obtained are diagnostic of conductive clay units. However, anomalously high resistivity values recorded are attributable to hydrocarbon invasion of some pore spaces. Dipole-Dipole field and theoretical pseudosections generated for the segment show predominance of conductive (clay) materials interspersed with slightly resistive (sand) materials beneath the southern half (1000 m) of the investigated segment. An isolated conductive feature (clay) was delineated beneath hydrocarbon pollution point. Finite Difference Method (FDM) inversion section of the investigated section however presents low resistivity materials (presumably clay) constituting the top segment within 180 – 970 m to depth of about 23 m. The section presents anomalously high resistivity constituents (diagnostic of severe hydrocarbon impact) at the lower segment in areas around 390 – 940 m and 1740 – 1870 m. Index Terms— Geo-tomography, hydrocarbon spill, pseudosections, Finite Difference Method (FDM). I. INTRODUCTION Pipeline rupturing or vandalization has become a disturbing facet of the Nigeria oil industry. While rupturing may be attributable to system failure or inadvertent action, vandalization presents a deliberate attack on the pipelines with intent to siphon the fluid for pecuniary purposes. The environmental degradation associated with spillage from oil pipeline present devastating consequences. Damages to the environment may remain for a very long period thus rendering the groundwater contaminated and unsuitable for use. Ezeh et al., (2014) described pipeline system as a medium of transportation usually used for conveying very sensitive products such as crude oil, natural gas and industrial chemicals, in which unattended problems in their operation 1Adeoye-Oladapo O.O., Department of Physics, Adeyemi College of Education, Ondo, Nigeria. Oladapo M.I., Department of Applied Geophysics, Federal University of Technology, Akure, Nigeria. results in unimaginable catastrophe. The economic, human and environmental consequences of oil spill are great (Rim-Rukeh, 2015). When oil spillage occurs, the beauty or the aesthetics of the ecology is damaged (Clinton et al., 2009). Oil introduced to the environment can elicit gross biological damage, physiological effects on the biota (both plants and animals) and a broad range of ecological changes (Briggs et al., 1996). Petroleum hydrocarbons can affect and cause changes in many organisms at all levels; cellular, organismic and ecosystems (Rim-Rukeh, 2015). Effects on marine organisms range across a spectrum from toxicity especially for light oils and products to smothering heavier oils and weathered residues (Rim-Rukeh, 2009). The presence of toxic components does not always cause mortality, but may induce temporary effects like narcosis and tainting of tissues, which usually subside over time. Other environmental impacts of oil spill may include: restriction of recreational use of such water bodies, non-availability of clean water for cooling purposes for industries located water bodies, and disruption of routine harbour activities such as ferry services (Osibanjo and Ajayi, 1989). In addition, when oil spills on surface of water bodies such as streams, rivers and lakes, it alters the quality of the water such that it makes it unfit for human consumption. It has been speculated that, one barrel of crude oil can make one million barrels of water undrinkable (Uzoekwe and Achudume 2011; Ordinioha and Sawyer 2010), disruption of fisheries activities (Rim-Rukeh, 2009), and most importantly oil spill have been reported to pose a significant potential for adverse human health effects (Getter et al., 1985). In tropical regions, mangrove swamps provide an extremely rich and diverse habitat as well as coastal protection and important nursery areas and in the event oil spill breathing roots of mangroves are smothered (NDES, 2003). At the study area, a pipeline conveying refined petroleum products from the Lagos port on the southern flank to storage tanks located north of the metropolis has suffered several rupturing and vandalization thus resulting in oil spill and fire outbreaks. Makinde and Tologbonse (2016) undertook oil spill assessment in Ijedodo (area of study) using geospatial technique and observed a steady decline of 29.1% in vegetation due to negative effect of oil spill from the pipeline. A deeper burial of the pipeline is therefore proposed to prevent the continual vandalization of the pipeline. However, a detailed subsurface stratification of the route needs be evolved to ensure incorporation of effective cathodic protection unit thus ensuring corrosion reduction. Electrical resistivity was adopted to evolve a tomography of the deeper pipeline route. In addition to the uses of tomography in Geoelectric Tomography Study of Hydrocarbon Spill at IJEDODO Area, Abule Ado, Lagos Adeoye-Oladapo O.O., Oladapo M. I.