Environmental Geochemical Assessment of Ogbagha River Sediments in Okpella Area of Edo State, Nigeria

Abstract

The main aim of this paper is the environmental geochemical assessment of Ogbagha river sediments to ascertain the level of their pollution. The study area lies between latitude 7°14’N and 7°22’N and longitude 6°15’E and 6°23’E in Okpella area of Edo State, Nigeria. Major and trace elements in the six composite samples collected were analysed using Epsilon-5 x-ray fluorescence model (pAnalytical). SiO₂ values range from
71.4-81.61 wt. % with mean of 75.71 wt %, while Al₂O₃ values range from 7.01-12.97 wt. % with mean values of 11.56 wt. %.The other major oxides are below 7.00 wt. %. SiO₂ and Al₂O₃ wt. % values are indicative of felsic source rock. The mean concentration values of Zr (1,830.55 ppm), Ba (1,416.00 ppm) and Cu (77.17 ppm) are higher than their crustal baseline values. Conversely, Sr (295.00 ppm), In (106.00 ppm), As (14.83 ppm), Cr (8.53 ppm), Co (7.00 ppm), Pb (13.33 ppm) have lower average concentrations than their crustal baseline average concentrations. Chemical index of alteration values for the samples also pointed to felsic source rock(s). The index of geoaccumulation values of Sb, In, Zr is indicative of serious environmental geochemical concern in the study area. However, potentially toxic elements such as Cu, Cr, Co, Pb, etc. are below the pollution baseline. It is recommended that standard environmental remediation measures should be taken to mitigate the pollution impact of In, Sb and Zr in the study area.

Keywords: Ogbagha-Okpella, environmental geochemistry, enrichment ratios, geoaccumulation index