Geology and Geochemical Assessment of Metal Contamination of Stream Sediments at Igun and Its Environs, Ilesha Area South Western Nigeria

Abstract

The cause of heavy metal contamination in stream sediments is probably related to mining activities in Igun study area. Hence the degree of contamination of major and trace elements was carried out to ascertain environmental impact assessment of Igun and its environs, the geology of the study area shows that talc schist, quartzite, amphibolite and granite are the major rock types within the study area, while petrographic studies show quartz, microcline feldspar, biotite, muscovite and hornblende as the main mineral constituents. Total numbers of ten (10) stream sediment samples were collected, air dried at room temperature and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) techniques. From the result of geochemical analysis of the stream sediment samples, the mean concentration for trace elements revealed that Manganese (Mn), Strontium (Sr), Zinc (Zn), Gold (Au) Nickel (Ni), Cobalt (Co) and Lead (Pb) have the mean values of 1704 ppm, 75.11 ppm, 55.80 ppm, 40.22 ppm, 26.15 ppm, 20.94 ppm, 10.60 ppm respectively. The contamination of metals was noticed from the geo accumulation index (Igeo), for stream sediments such as Nickel (0.1), copper (0.5), Manganese (0.6) with Igeo < 1 depicting that these metals are practically uncontaminated. Cobalt (0.1), Zinc (1.1) with Igeo number > 1 < 2 are moderately contaminated and Gold with Igeo of (9.6) indicate very high contamination. In conclusion the results shows that some part of the study area are contaminated and this includes Imoo (location 4), Owena (location 9) and Oke-Ipa (location 1) compared to other locations in the study area which are not contaminated.