Geoelectrical and Physicochemical Characterization of Groundwater Contamination around a Cassava Processing Factory in Ogbomoso, Southwestern Nigeria

Abstract

2D resistivity profiling and hydro-geochemical analyses were carried out to assess groundwater contamination. in and around the Cassava Processing Factory at Aarada, Ogbomoso, Southwestern Nigeria. The dipole-dipole profiling was conducted along eight traverses, trending NW-SE, using electrode spacing a = 5m and expansion factor n=1 to 4. The resistivity data were inverted using 2D inversion procedure to produce the 2D inverted resistivity sections beneath the traverses. Water samples were also taken from seven hand dug wells within and around the study area for physicochemical analyses to determine the pH, EC, TDS, and concentrations of cations and anions which included Fe2+, Zn2+, Na+, Pb2+, Cu2+, K+, NO3ˉ and CN-. The 2D inverted resistivity sections revealed that the study is characterized by relatively low resistive zones typical of contamination plumes beneath the traverses near the cassava processing factory and general dumpsite. The pH values range from 7.2 to 8.0 and indicate that the groundwater is basic. They are within the WHO (2011) recommended limits. The electrical conductivity (EC) and total dissolved solids (TDS) exceed the WHO limit in the wells close to the cassava processing factory and the dumpsite, indicating that the water is harmful to human health. The major indicators of groundwater contamination in the study area are the Fe2+ and NO3ˉ caused by percolation of the dumpsite leachate, and CN- caused by infiltration of the cassava effluent, into the aquifers. The level of contamination in the wells is closely related to proximity to the cassava processing factory and the dumpsite. The discharge of the effluents from the cassava processing factory contributes significantly to cyanide contamination of groundwater in the study area. Appropriate remediation measures should be taken to forestall further contamination of groundwater in the study area.