Spatial distribution of trace element of Ala river's sediments, Akure, Southwestern Nigeria

Abstract

Thirty six river sediment samples were collected from Ala River, Akure, and were analysed by ICP-MS for 14 chemical elements including Cu, Pb, Zn, Ni, Co, Mn, As, U, Th, Sr, Cd, V, La, and Cr. The concentration levels of the metals ranged from 0.26 μg/g in Cd to 3719.00 μg/g in Mn. Strong variations in sediment geochemistry were observed from one sample location to the other. Several hot-spot areas were located close to areas where activities such as vehicle related workshops, road junctions, municipal waste, abattoir and farm gardens were identified. The concentration levels of Pb (19.13-164.54 μg/g), Mn (354-3719 μg/g) and Zn (49.30-749.50 μg/g) were of environmental concern because of their relatively high concentrations in the sediments, at some locations, when compared with the average earth crust background limit. Most of the other elements did not show much contamination load as compared with the average earth crust background limit. The geoaccumulation index (I-geo) values showed that the sediments were contaminated with Pb, Zn and Cu. Metals such as Pb, Zn, Cu, Cr, Mn, Ni, As, Cd and V were positively correlated with each other (r = 0.51-0.95), which indicated analogous sources of geochemistry characteristics. The study showed that anthropogenic activities greatly contributed to enrichment of trace elements in Ala River sediments.

Keywords: Ala River, Sediment, Geo-accumulation index, spatial variation, anthropogenic