•Oxidation and reduction reactions give rise to leachate production from dumpsites.
Geophysical methods give contrasting signatures in dumpsite contaminated environment.
The flow models give the groundwater/contaminant flow direction and flow rate.
The first order geoelectric parameters give rise to the conceptual model.
Indiscriminate dumping of both domestic and industrial waste has been increasing since the beginning of the exploration and exploitation of hydrocarbon in the Niger Delta area of Nigeria and has impacted the groundwater quality. Therefore, this study seeks to evaluate contaminant hydrology from dumpsite around Ujevwu area in relation to a Control site. Three Electrical methods, which include the spontaneous potential, dipole-dipole and the vertical electrical sounding were adopted. Also laboratory water analysis and groundwater/contaminant modelling using VISTA, version 4 were used to evaluate groundwater quality and flow direction/velocity. The low values of 11–515 Ωm and 10 to −160 mV for resistivity and spontaneous potential respectively around the dumpsite area to a depth of about 20 m is a reflection of the redox phenomenon occurring at depth in the contaminated groundwater. Hydrogeochemical parameters from water analysis showed values that are higher around the dumpsites when compared to the control site. Results for conductivity, lead and total viable bacteria count are higher than the permissible limits of the World Health Organisation (WHO) and they range from 380 to 440 μs/cm, 0.2–0.3 mg/l and 4.2–15.8 cfu/mL respectively. The steady state groundwater distribution model of the dumpsite and control site gives an approximate head gradient of about 0.00036 and 0.0007 respectively, and the flow direction in the south west. It is observed that the water level indicates that there is no significant change of the hydraulic gradient with time and therefore, the groundwater flow is assumed to be in steady state with the flow direction in the NE-SW, and a flow rate of 0.0093 m/d or 3.3 m/year, and 0.0197 m/d or 7.0 m/year respectively. From these results, immediate evacuation of the dumps in the area and remediation program should be carried out, as there is a risk of outbreak of water borne diseases in the area.
Geophysical assessment for contaminant hydrology in Ujevwu, Nigeria
Categories: Research development