Delineation of leachate plume migration and appraisal of heavy metals in groundwater around Emirin dumpsite, Ado-Ekiti, Nigeria

Abstract

Leachate from solid waste has been identified as a major source of pollution that threatens groundwater resources worldwide. Thus, the leachate contamination status and the heavy metals health risk assessment of the Emirin dumpsite were investigated using integrated Electrical Resistivity Imaging (ERI) and hydrochemical methods. The ERI survey comprised four 2-D profiles created with a dipole-dipole electrode array and a minimum electrode spacing of 5 m. Also, groundwater samples were collected from five wells around the dumpsite for hydrochemical analysis and the groundwater hydrochemical facies and irrigation parameters were evaluated. The health risk associated with heavy metals ingestion were as well assessed using health risk parameters such as average daily intake (ADIing), hazard quotient (HQ) and hazard index (HI). The inverted model from the ERI survey reveals thread of leachate incursion from the dumpsite identified as low resistivity signatures (<20 Ωm) within the thin porous overburden units overlying the fresh bedrock. Results of hydrochemical analysis reveal that the groundwater comprises of cations (K+>Na+>Ca2+>Mg2+) and anions (Cl−>HCO3−>SO42−) in relative abundance. Most physicochemical contents fall within the admissible World Health Organization (WHO) standards for drinking water and the groundwater hydrochemical facie reveals sodium-bicarbonate-chloride water type. However, the concentrations of nickel, iron, lead and chromium reported in this study are higher than the WHO prescribed standards, indicating that the groundwater is deteriorating, which could be attributed to leachate incursion from the nearby dumpsite. Irrigation indices suggest that groundwater sourced from the study area is suitable for agricultural purposes. The sequence of HQ due to heavy metals follows the order of Cr>Pb>Cu>Mn>Zn>Ni>Fe for both age population considered. While the HI values were estimated to be 1.93 for adults and 8.97 for children, implying that adults and children in the study area are prone to non-carcinogenic health challenges.