Abstract

Surface water pollution poses a major risk to all biotic entities dependent on the water body. This study assessed the surface water quality of commodore channel, Lagos lagoon with respect to its heavy metals pollution level using indexing approach to determine the sources of heavy metal and its associated pollution risk. Samples were collected at a depth of 10-15 cm within a distance of 4 km from the shore line. Metal concentrations were evaluated using Atomic Absorption Spectrometry. The Concentrations of Pb (0.203-2.601 mg/L), Fe (0.253-1.049 mg/L), Cd (0.017-0.133 mg/L), and Co (0.000-0.226 mg/L) exceeded the recommended limits set by the World Health Organization, while Zn concentration (0.007-0.319 mg/L), was within acceptable limits for all locations investigated. Heavy metal pollution index (HPI) of the study area was found to be 3532.1, exceeding the critical pollution index value of 100. Similarly, the Metal Index (MI) of 150.5 of the study area was above threshold limit value of 1, suggesting that the area is seriously polluted with heavy metals. Sample t-test, confirms that there is a significant statistical different (with p value at p<0.05) between samples collected from the industrial areas and non-industrial area. The study revealed the sources of the heavy metals are primarily from anthropogenic source attributed to the untreated industrial discharge, and municipal solid waste disposed in the area. Prompt enforcement of environmental protection laws is needed to prevent continuous pollution of the area. 

Key words: Water quality, heavy metals, atomic absorption spectrometry, surface water, heavy metal pollution index, metal index.