ANALYZING THE EXTENT OF LEACHATE FROM A MAJOR DUMPSITE WITHIN THE CRETACEOUS SEDIMENTS OF IKOM-MAMFE EMBAYMENT, SOUTHEAST NIGERIA

Abstract

Groundwater resources in the region serve as a vital source of potable water for local communities and are essential for supporting various socio-economic activities. Unfortunately, the infiltration of leachate from dumpsite contributes to the dispersion of contaminants within the cretaceous sediments, posing a potential threat to groundwater quality. This study presents an exhaustive examination of leachate extent emanating from a prominent dumpsite situated within the Cretaceous sediments of the Ikom-Mamfe Embayment, Southeast Nigeria. Employing meticulous soil sampling methodologies and water collection from strategically positioned boreholes near the Ikom dumpsite, advanced techniques such as Electrical Resistivity Tomography (ERT) and Vertical Electric Sounding (VES) were utilized to scrutinize the infiltration of leachate within the site. Laboratory analyses were conducted to evaluate the concentrations of heavy metals, including Lead, Mercury, Arsenic, Nickel, Chromium, and Cadmium, in both soil and borehole water samples. The findings unveiled alarming levels of Lead and Cadmium concentrations in the soil, exceeding established regulatory thresholds, with recorded values ranging from 552.34 to 556.93 mg/kg and 11.88 to 7.46 mg/kg, respectively. Similarly, borehole water analyses in the vicinity of the Ikom dumpsite revealed elevated concentrations of Arsenic, Lead, Cadmium, and Nickel, surpassing WHO limits in specific boreholes (BH2 and BH3), indicative of potential soil porosity issues and unfavorable geological conditions prevalent in the study area. Notably, the use of ERT delineated an inverse resistivity of 5.99 Ωm at a depth of 9.26 m, pinpointing the leachate-infiltrated cretaceous sediments zone, extending laterally from 10m to 40m along the profile. The observed infiltration of leachate at 9.26 m depth underscores its penetration into the sandstone, shale, and dark gray shale strata within the dumpsite. Furthermore, the quantified thickness layer ranging from 1.41 to 4.37 affirmed leachate infiltration within the sandstone, shale, and dark gray shale strata, with implications for its movement and containment dynamics. This study underscores the critical role of layer thickness in influencing the migration and containment of leachate, with thicker layers potentially acting as barriers to its movement, while thinner layers may facilitate more rapid migration. Additionally, the assessment of aquifer protective capacity, denoted by ratings below (<0.1), underscores the poor protective capacity of the aquifer system in the study area. In light of these findings, strategic management, remediation, and vigilant monitoring measures are advocated to mitigate contamination risks and safeguard water quality.