Spatio-Seasonal Evaluation of Heavy Metal Pollution, Water Quality, and Ecological Risk in Lake Chad Ecosystem

Abstract

This study presents a spatio-seasonal assessment of heavy metal pollution, water quality, and ecological risk in the Nigerian sector of Lake Chad, focusing on five strategic locations (LC1–LC5) sampled during dry (January–February) and wet (July–August) seasons. Physico-chemical parameters (pH, EC, TDS, DO) and concentrations of heavy metals (Pb, Cd, Cr, Zn, Cu) were evaluated. The results showed that pH values ranged from 6.8 to 8.1, while EC and TDS were elevated during the dry season, indicating concentration due to evaporation. Peak concentrations of Pb (0.15 mg/L) and Cd (0.013 mg/L) were observed at LC3 and LC5 in the dry season, exceeding WHO limits of 0.01 mg/L and 0.003 mg/L, respectively. Pollution indices revealed Igeo values for Pb and Cd ranging from 0.6 to 1.8, indicating moderate to strong pollution. CF values for Cd exceeded 3 at LC5, classifying it as considerably contaminated. PLI ranged from 1.3 to 2.1, confirming pollution across all sites, while RI values indicated considerable ecological risk at LC3 and LC5 (up to 297.9). Pearson correlation (r = 0.88 between Pb and Cd) and PCA implicated anthropogenic sources such as agricultural runoff and industrial discharges. These findings highlight the urgent need for pollution control strategies and sustainable water resource management in the Lake Chad Basin.