Application of seismic refraction tomography for subsurface imaging in central northern Nigeria.

Chiemeke, CC; Osazuwa, IB

doi:10.4314/njphy.v19i2.38141

Cited by 1 publication

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“…7). Borehole logs from the surrounding and Previous resistivity survey in the study area (Chiemeke, 2005;Chii, 2001;Jegede, 2009;Jegede et al, 2011) suggest that the weathered overburden is characterized by resistivities in the range of 50 to 200 Ohm-m, therefore in the neighborhood of the dumpsite, it is expected to occur as a relatively thick layer of contaminant zone, in that case, the resistivity of shallow regolith might be expected to be less than 50 Ohm-m. Since the water table is shallow and regolith is largely saturated, any resistivity much below 20-Ohmm will indicate groundwater contamination, in the absence of clay materials.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

Near-Surface Investigation of Groundwater Contamination in the Regolith Aquifer of Palladan, Zaria using Borehole log and Tomography Techniques

Jegede¹,

Iserhien-Emekeme²,

Iyoha³

et al. 2013

RJASET

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Two geophysical Tomography techniques-Electrical resistivity and Seismic refraction were used to investigate the subsurface of a potentially polluted dumpsite in Palladan a densely populated area of Zaria, with a view to examining the possible subsurface distribution of groundwater contamination plume. The presence of domestic wells in the residences of the people which are distances 10.0 to 30.0 m from the dump facilitated analysis of water chemistry to enhance the geophysical interpretation. The groundwater level in the dumpsite site was found to be higher than the surrounding area, thereby creating a local deviation from the regional groundwater flow. Due to this the contaminants from the waste site spread out in the nearby soil and groundwater. The resistivity models clearly show a top layer of about 10.0 m thickness with low resistivity, whereas the resistivity has an inverse correlation with distance from the waste disposal site. Bore hole log shows that the top upper 10.0 m of soil consists of loose permeable laterite with high water content followed by a layer of degraded sand before the weathered basement which suggests the possibility of the contamination penetrating deeper into the regolith aquifer. This agrees with the result of the water chemistry analysis which shows elevation in concentration of contaminants above the WHO guidelines. The borehole log also indicated the presence of fracture basement at a depth of 23.0 m this correlated well with the Seismic refraction result. The study therefore suggests that these fractures also facilitate the migration of the contaminants. Based on the combined results, the contamination plume seems to have migrated not less than 500.0 m in the southern direction which is also the direction of hydraulic gradient.

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Section: Discussion Of Resultsmentioning

confidence: 99%