Spatio-Temporal Assessment of Heavy Metal Contamination in Borehole Water of Bali Town, Taraba State, Nigeria

Abstract

Ensuring access to safe drinking water remains a public health priority, especially in rural Nigeria where boreholes are the major source of water. This study investigated the spatiotemporal distribution of heavy metals in borehole water in Bali Town, Taraba State, focusing on lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and copper (Cu). Ten boreholes were sampled during both dry (March–May) and rainy (June–August) seasons. Physicochemical parameters were measured in situ, while heavy metal concentrations were determined using Atomic Absorption Spectroscopy (AAS). The results showed that Pb (0.01–0.04 mg/L) and Cd (0.001–0.006 mg/L) exceeded World Health Organization (WHO, 2022) limits in several boreholes, with higher values recorded during the rainy season. Ngang-Dole, Suntai, and Takalafiya emerged as contamination hotspots, while Bali A and B recorded the lowest levels. Chromium and arsenic were also elevated in some locations, with Cr peaking at 0.06 mg/L and As at 0.03 mg/L. Copper concentrations ranged from 1.0–4.0 mg/L, with three boreholes surpassing the WHO guideline of 2.0 mg/L. These findings highlight both spatial variability and seasonal influence on groundwater quality. The study concludes that borehole water in Bali Town is at risk of heavy metal contamination, posing long-term health hazards including kidney dysfunction, developmental delays, and cancer risks. It recommends routine groundwater monitoring, stricter regulation of agrochemical use and waste disposal, community sensitization on water safety, and adoption of low-cost water treatment technologies to safeguard public health. The study is anchored on the Pollution Pathway Model, Hydrogeological Risk Framework, and Exposure-Dose-Response Model, which guided the interpretation of the findings.