Assessment of Heavy Metal Pollution of Wetland Soils in Ijokodo, Oyo State, Nigeria

Abstract

Wetlands soils play significant roles in agricultural food production, but are susceptible to heavy metal contamination from recharge waters and/or agrochemicals. This study investigated distribution and level of pollution of heavy metal in soils of Ijokodo wetland, Oyo state, Southwest Nigeria. Twenty soil samples (top and sub soils) were collected randomly within the wetland in October, 2019 and analyzed for Mn, Fe, Cu, Zn, Pb, Cd, Co, Cr and Ni using standard methods. The degree of heavy metal pollution was assessed by comparing metal concentrations to sediment quality guidelines and soil quality thresholds. The results show that soil within the Ijokodo wetland is moderately polluted with cadmium and nickel at concentrations that could cause adverse impact to the wetland ecosystem. The correlation matrix and PCA both show recharge waters, agricultural inputs and parent rock composition as important sources of metals in the wetland. The presence of heavy metals in wetland soils above permissible limits is of human health concern and calls for continuous monitoring of Ijokodo wetland soils to check heavy metal enrichment above the accepted regulatory limits.