Petro Chemistry of Major and Trace Elements Concentrations in the Stream Sediments of Awo Area and its Environs, Southwestern Nigeria.

Abstract

Stream sediments are believed to record the environmental impact on fluvial system overtime and are often study to determine the overall pollution of an environment. This research work is aimed at mineralogical appraisal of various rock types through petro logical study, also to estimate the degree of enrichment of the element in the stream sediments and to determine if such enrichment has led to any form of pollution and also to produce a baseline geochemical data base for further geochemical investigation of the area under investigation.

Ten soil samples were collected randomly within the study area and were analyzed for major and trace elements concentration using the Inductively Coupled Plasma Mass Spectrometry (ICP-MS) instrumentation techniques, while five rock types were selected for petro graphic studies.

Thin section study shows that muscovite, biotite, microcline, and quartz are the main mineral assemblages present in the rocks of the study area. The result of the geochemical analysis were thereafter subjected to multivariate statistical analysis, the statistical plot from the result of major elements shows that Iron oxide (Fe₂O₃)  range from 9.30% - 1.60 %, with a mean value of 4.6865%. Aluminum oxide (Al₂O₃) range from 2.63% - 0.55% with a mean value of 1.6802%, Fe₂O₃ and Al₂O₃ are dominant major oxides within the study area and they show moderate enrichment in the environment under investigation.  From the result of the trace elements, Manganese [ Mn] with mean value of 3996.00 ppm, Zinc [Zn] with mean value of 272.40 ppm,  Copper [Cu]  with mean value of 628.10 ppm, Lead [Pb] with a mean value of 61.22 ppm, Nickel [Ni] with a mean value of 109.40 ppm and Cobalt [Co] with  mean value of  89.0 ppm have high concentration within the area of study, with Copper [Cu] having the highest degree of contamination factor 33%. The enrichment of Lead [ Pb] in the study area has been linked to anthropogenic  input of exhaust from motor bikes that ply the area, very strong positive correlation exist between V and Cr  (0.737), Co and Ni (0.648) while a positive strong correlation exist between Co and Cr (0.550), Mo and Ga  (0.535) indicating that they are from the same source.

The conclusion drawn from the box plot study show that V, Cr, Co, Ni, Zn, Mn, As,  Rb,  Pb, Mo, Ga and Cd have values that are greater than zero, while Sr and  Zr have values that are less than zero. Copper [Cu] is the highest contaminating element within the study area, the presence of high amount of cupper in the study area may be probably due to geogenic factor, and in addition the  weathering of the associated rocks and precipitation of same within the environment and it can also be attributed to the mining operations going on in the study area; from this it can therefore  be deduced  that the study area range in the category of practically contaminated to moderately contaminated.

Keywords: Sediment, Biotite, Enrichment, weathering, Geogenic