Seasonal and Spatial Dynamics of Heavy Metals Contamination in Oguta Lake, Imo State, Nigeria

Abstract

This study investigated the seasonal and spatial dynamics of heavy metal contamination in Oguta Lake, Nigeria, with implications for ecological integrity and public health. Water samples were collected from three stations (upstream, midstream, downstream) during dry and rainy seasons and analyzed for eleven metals (Pb, Fe, Co, Ag, Ti, Cr, Cu, V, Zn, Mn, Ni) using Atomic Absorption Spectrophotometry. Results revealed significant seasonal and spatial variations (p < 0.05). Pb (6.7–13.3 mg/L) and Fe (11.5–35.3 mg/L) were highest upstream, Zn (13.1–22.7 mg/L) and Mn (0.12–1.27 mg/L) peaked midstream, while Ni and Co were elevated downstream, particularly in the rainy season. Mean concentrations followed the order Fe > Zn > Pb > Mn > Ni, with several metals exceeding World Health Organization permissible limits. Correlation analysis revealed strong associations between Pb and Fe, and between Zn and Mn, across both seasons. A Ni–Co relationship emerged during the rainy season, suggesting a combined geogenic and anthropogenic influence. The findings highlight Oguta Lake as a hotspot of heavy metal pollution, emphasising the urgent need for continuous monitoring, watershed management, and the provision of safe alternative water sources to protect the surrounding communities.