Geochemical and Mineralogical Assessment of Sediments in Canal and Lagoon Parts of Lagos, South-western, Nigeria

Abstract

Indiscriminate dumping of refuse and discharge of untreated industrial waste into the drainage systems and vehicular emissions has affected the quality of most sediments deposition for its geological and civil engineering purposes. This work is based on the assessment of sediments in canal and lagoon parts of Lagos, Nigeria, for its geochemical and mineralogical formation. The clay fraction (< 63µm) in the sediments was processed and analyzed for their heavy metal contents using Atomic Absorption Spectrometry (ICP-MS) respectively. The sediments were also studied for their mineralogical compositions by X-ray diffraction. The clay mineralogy is predominantly consisting of Kaolinite, Geothite and Quartz. The results of heavy metals in sediments showed that canal sediments consist of Pb, Zn, Cu, As, Co, Cr, Cd, Hg, Fe, and Ni while lagoon sediments are Pb, Zn, Cu, As, Co, Cr, Cd, Hg, Fe, and Ni. Based on the Geo-accumulation indices, the sediments are unpolluted with respect to Zn, Cu, Ni, Co, Cr, and Fe. However, the canal and lagoon sediments are variably polluted with respect to Pb, As, Cd, and Hg. In the case of Cd, the sediments are highly are highly polluted. As far as Hg is concerned both sediments of the canal and lagoon are very highly polluted. With the exception of copper having (KD) value less than 1. Possible contamination sources are from industrial and anthropogenic sources. These need to be monitored and controlled effectively.