Assessment of trace metal contamination by geochemical normalisation in sediments of two lagoons: A comparative study of the Kpeshie and Muni lagoons, Ghana

M K Dorleku,D K Amoah,L Yawson,I O Hodgson,K M Kumi,C Tay

doi:10.4314/gjs.v62i1.4

Abstract

Heavy metal contamination status of bottom sediments of two lagoons was compared by the employment of Enrichment Factor (EF) analysis for Iron (Fe), Manganese (Mn), Cupper (Cu), Lead (Pb), Chromium (Cr), Nickel (Ni), Silver (Ag), Zinc (Zn) and Mercury (Hg). Kpeshie Lagoon recorded enrichment (EF ≥ 1) for Cd, Pb, Ag, Hg and Zn, whilst Muni Lagoon recorded enrichment for Cd, Mn, Ag, Hg and Zn as metals of anthropogenic influence. Kpeshie, situated in a highly urbanized area, has 75% spatial distribution of Pb enrichment. The assessment shows that Ag and Hg are the most enriched metals in the sediments of both Lagoons, reaching extremely severe levels. Only Mn showed statistically significant difference in mean concentration of metals for both Lagoons. Pearson correlation matrix indicated that Pb had a strong relation with Ag, Hg and Zn (r = 0.956; p < 0.05) which is significant in Kpeshie. It also had a strong association with Ag and Hg but not with Zn (r = 0.240) in the Muni. The study clearly delineates Pb as a pollutant that designates the urban status of Kpeshie. Its associated metals; Ag, Hg and Zn which may be coming from a common source are from industrialized zones.

Highlights

Lagoons form part of wetland ecosystems that are made up of soils and water as well as plants and animals
The average shale value for Fe is 47200 which is far higher than what was obtained for the two Lagoons, indicating non-anthropogenic input in the sediment of both Lagoons
Kpeshie Lagoon recorded enrichment for Cd, Pb, Ag, Hg and Zn which is indicative of anthropogenic influence, whilst Muni recorded Cd, Mn, Ag, Hg and Zn as metals of anthropogenic influence with Mn replacing Pb, even though station MM recorded some Pb enrichment in the scenario

Summary

Introduction

Lagoons form part of wetland ecosystems that are made up of soils and water as well as plants and animals. The values in all the stations in Muni showed minor enrichment (EF ≥ 1) whilst that of Kpeshie recorded no enrichment (Table 6), clearly indicating that the presence of Mn in sediments of Kpeshie Lagoon is principally from natural sources. There was a significant difference between the mean concentrations of Muni and Kpeshie (p = 0.019), p < 0.05, further indicating that Muni was anthropogenically enriched.

Results

Conclusion