Leachate-Impacted Groundwater: Physicochemical Assessment And Health Risks In Mbodo Aluu, Ikwerre Local Government Area, Rivers State, Nigeria
Okidhika, C. U.
Department of Chemistry, Faculty of Natural and Applied Sciences, Ignatius Ajuru University of Education, Rumuolemini, Port Harcourt, Rivers State, Nigeria
Onuchuku P.U.G
Department of Chemistry, Faculty of Natural and Applied Sciences, Ignatius Ajuru University of Education, Rumuolemini, Port Harcourt, Rivers State, Nigeria
Keywords: leachate, groundwater contamination, Mbodo Aluu, physicochemical parameters, heavy metals, health risk assessment, WQI, Piper diagram, Rivers State, Nigeria
Abstract
Open dumpsites represent a persistent and poorly regulated source of leachate contamination that threatens shallow groundwater quality in peri-urban communities across sub-Saharan Africa. This study assessed the physicochemical and microbial quality of groundwater from five boreholes (BW-1 to BW-5) located at increasing distances (50–600 m) from the Mbodo Aluu open dumpsite, Ikwerre Local Government Area, Rivers State, Nigeria, with one control borehole (BW-6) established in an unimpacted location 1.2 km from the dumpsite. Sampling was conducted in triplicate across four seasonal episodes (December 2023 – November 2024). Physicochemical parameters, ten heavy metals (Fe, Mn, Pb, Cd, Cr, Ni, Zn, Cu, As, Hg), and microbial indicators were determined following APHA (2017) standard methods, flame atomic absorption spectrometry (F-AAS), and membrane filtration techniques. The Water Quality Index (WQI) for BW-1 (50 m from dumpsite) was 187.6, classified as Unsuitable for Drinking. All ten heavy metals exceeded WHO (2022) and NSDWQ (2015) permissible limits in BW-1 and BW-2. Lead (0.187 ± 0.009 mg/L), cadmium (0.024 ± 0.001 mg/L), arsenic (0.068 ± 0.003 mg/L), and chromium (0.142 ± 0.007 mg/L) recorded the most severe exceedances in BW-1. Human health risk assessment following USEPA (2020) guidelines yielded a cumulative Hazard Index (HI) of 3.154 across all metals in BW-1, indicating unacceptable non-carcinogenic risk. Carcinogenic risk estimates for Pb (3.12 × 10⁻⁶), Cd (4.84 × 10⁻⁶), Cr (6.12 × 10⁻⁶), and As (9.52 × 10⁻⁶) fell within the USEPA acceptable range (10⁻⁶–10⁻⁴). Microbial analysis confirmed total coliform counts of 2,840 ± 124 MPN/100 mL and E. coli of 684 ± 32 MPN/100 mL in BW-1, far exceeding the WHO zero-tolerance threshold. Piper diagram and Gibbs plot analyses classified the water hydrochemical facies as Ca-Mg-HCO₃ type with progressive anthropogenic enrichment in Na⁺ and Cl⁻ with increasing leachate impact. The study underscores the urgent need for engineered dumpsite closure, groundwater protection legislation, and community water supply intervention in Mbodo Aluu.