EXTENT OF LEACHATES INFILTRATION IN A TYPICAL CASSAVA PROCESSING SITE USING INTEGRATED ELECTRICAL RESISTIVITY TECHNIQUES AND ASSOCIATED WATER-LEVEL MEASUREMENT IN APETE SOUTH-WEST NIGERIA

Abstract

Environmental assessment and subsurface illuminating strength of integrating electrical resistivity method of geophysical investigation techniques comprising 2D Electrical Resistivity Method (ERM) adopting Wenner configuration, Vertical Electric Sounding (VES) and water level measurements from four (4) separated hand-dug wells to investigate and evaluate the extent of subsurface leachate infiltration of contamination plume in a cassava processing mill of Apete, South-West Nigeria was conducted in the study area. A total of five (5) 2D profiles (four within the study area while the fifth 40m from the investigated area; being the control site were carried out alongside three (3) VES with a length of 50m each. The electrodes were arranged along a line with a constant spacing between adjacent electrodes. The electrodes were connected to the cable which was connected to the resistivity meter (CAMPUS Ohmega). The minimum electrode spacing used was 10m (for data level n=1) while the maximum electrode spacing used was 50m (for data level n=5). The results showed distinct resistivity zones namely, Leachate plume in topsoil (5-13Ωm), impacted zone (13-120Ωm), and no impact zone (130-550Ωm) in Traverse 1; High impact zone with leachate dominance (10-20Ωm), impacted zone (20-85Ωm), and no impact zone (100-500Ωm), in Traverse 2; Dominant no impact zone (25-120Ωm) with minor leachate intrusion in Traverse 3; No impact zone (20-70Ωm) dominates (90%), minor leachate intrusion (3%), and slightly contaminated area (7%) in Traverse 4 while Leachate present in minor quantity, slightly/partially contaminated zone (13-60Ωm) dominates (85%), and high resistivity zone present in minor quantity was encountered in Traverse 5 with leachates  impacting the subsurface to the level of 14m in traverse 2 while the results of VES 1 and VES 2 indicating that the leachates have contaminated the subsurface with indicated low resistivity. The results of the water level measurement obtained from the existing wells indicated a depth of 1.77m in APWW1 (Apete well water) as the lowest depth and 4.60m in APWW4 as the highest depth. The aforementioned results revealed that the soil and shallow groundwater system notably the hand-dug wells within and around the investigated are vulnerable to contaminant seepages emanating from the surface with unprecedented impacts on the study area if no precautionary measures are undertaken.