Evaluating the Impact of a Dump Site on Groundwater Quality in Barikin-Sale, Minna, North-Central Nigeria

Evaluating the Impact of a Dump Site on Groundwater Quality in Barikin-Sale, Minna, North-Central Nigeria.

Abstract:
Groundwater pollution resulting from the discharge of leachate from refuse dumpsites poses significant environmental concerns. In this study, a geophysical investigation was conducted on an uncontrolled open solid waste dumpsite located in the Barikin-Sale area of Minna, with the aim of assessing the potential contamination of groundwater due to leachate percolation. The investigation involved ten (10) Vertical Electrical Sounding (VES) points and two (2) 2D Subsurface Electrical Imaging surveys, both inside and outside the dumpsite, to evaluate leachate migration in the area.

For the VES, a Schlumberger configuration was employed, while the Wenner configuration was used for the subsurface imaging. The VES data analysis identified three geoelectric sections: topsoil, weathered basement, and fractured/fresh basement, with apparent resistivity values ranging from 19.4 Ωm to 122.6 Ωm for the topsoil, 18.2 Ωm to 33.4 Ωm for the weathered basement, and 93.5 Ωm to 166.4 Ωm for the fractured/fresh basement. The thickness of the topsoil layer ranged between 0.9 m and 1.8 m, while the weathered basement layer had a thickness of 4.0 m to 5.3 m.

The 2D resistivity data were processed and inverted using the RES2DINV software, revealing areas with low resistivity values (<20 Ωm), attributed to leachate derived from decomposed waste, and areas with slightly higher resistivity (>20 Ωm) representing non-decomposable waste deposits. Some areas showed the highest resistivity values (>100 Ωm), which were interpreted as chemical weathering products of the crystalline bedrock, likely regolith.

To complement the geophysical findings, sieve analysis of soil samples from four pits showed that the soils were fine to medium sand, and hydraulic conductivity values ranged between 1.97 x 10-4 and 2.52 x 10-5 m/s, corroborating the geophysical investigation results.

Physicochemical analyses of ten (10) water samples from hand dug wells and boreholes revealed concentrations of conductivity, TDS, and nitrite exceeding permissible limits set by NSDWQ (2007) and WHO (2010) in some locations, indicating groundwater contamination. However, median and mean concentrations generally fell within the permissible limits.

Based on the results, it is evident that leachates are concentrated in the lower part of the dumpsite, posing a threat to groundwater sources in the surrounding environment due to potential leachate contamination.

Evaluating the Impact of a Dump Site on Groundwater Quality in Barikin-Sale, Minna, North-Central Nigeria.

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