Assessment of River Asa Catchment Soil for Heavy Metal Pollution Using Indices Methods

Abstract

Lack of water for irrigation purpose has in recent time led to the use of catchment soil of polluted river for agricultural practice of farming. This study was aimed at investigating the contamination status of catchment soils of Asa River, Ilorin, Nigeria. Soil samples were collected from four sampling stations; Before Asa Bridge, In front of Asa Bridge, Emir Bridge and at Unity Bridge. The samples were analysed to determine their heavy metals (Fe, Cu, Mn, Pb and Zn) concentrations using Atomic Absorption Spectrophotometer (AAS). The obtained results for the metal concentration were used for Pollution Index computation. The contamination factor, degree of contamination, modified degree of contamination, pollution load index and geoaccumulation indices were all employed. The values of all the metals considered, except Fe were higher at second to fourth location than those from the first location (control) suggesting probable influence of anthropogenic activities on the catchment soil. The Indices results which reflect the cumulative effects of all the metals showed that the first location has a relatively low level of contamination while other locations indicated contamination status of the soil. The implication is that there is every tendency of transmission of heavy metal to man from plant through food chain and thus planting of edible phytoplant on the soil should be avoided.