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Author(s): Egwuonwu Gabriel N., Okpala Paul K..

Volume/Issue: Volume 3 , Issue 3 (2020)

Abstract:

The vulnerability of overburden aquifers at the vicinity of a municipal dumpsite has been carried out. The survey site is bounded by longitude 7°5'20''E and 7°5'52''E and latitudes 6°13'35''N and 6°13'52''N located within Niger delta basin of Southeastern Nigeria. Two-dimensional electrical resistivity tomography (2DERT) and vertical electrical sounding (VES) techniques were carried out in order to ascertain the extent of the vulnerability of groundwater at shallow subsurface. The registered resistivity values modeled in the 2DERT and VES are in the ranges of about 3.76 Ωm to 11464 Ωm and about 76.79 Ωm to 5665.85 Ωm respectively. With the aid of Res2D inversion version 3.2 and Winglet version 1.62 software, the 2DERT and VES data were modeled respectively. Interpreted 2DERT results showed evidence of the leachate in clayey and sandy topsoil the refuse dump. Inferred fractures in both top and other shallow layers suggest percolation of the leachate into depths beyond the limits probed by the 2DERT. Interpreted results from the VES showed that longitudinal conductivities S_L derived for depths in the study site is in the range of about 0.002161 - 0.101741 mhos. Hence, Dar Zarrouk Parameter (DZP) standard was used to evaluate the protective capacity of groundwater’s overburden at the site and its vulnerability. Based on the interpreted 2DERT, there is evidence of leachate percolation through the topsoil and shallow subsurface to depths. The protective capacity of the depths underlain by the groundwater was inferred as weak at NNE and Eastern zones of the dumpsite while at the SSE and the Western zones of the dumpsite was inferred as poor. Consequently, the vulnerability of the groundwater in the vicinity of Awka municipal dumpsite to percolating leachate from refuse dump is moderately high.

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