Seasonal Variations of Toxic Metal Pollution in Soil and Sediment Around Okaba Coal Mine Area, Kogi, Nigeria

Abstract

Pollution by heavy metals presents one of the most potent threats to soil and sediment resources as well as human health. This research was carried out to determine pollution level of the heavy metals in soil and sediment and their seasonal variations in concentrations. Both dry and wet seasons soil and sediment samples were investigated for metal pollution and seasonal variations at Okaba coal mine area. The soil and sediment samples were collected in dry and wet seasons, prepared and analysed using Atomic absorption Spectrometer (Perkin Elmer model 31000), AAS. The degree of pollution and seasonal variations among metals within the sampled media were established using index of geoaccumulation (Igeo), enrichment factor (EF) and contamination factor (CF). The average values of the three (3) indices used showed that most metals under investigation have impacted on the soil and sediment in both seasons at different degrees. It was generally observed that the wet season concentration values were lower than the dry season concentrations. This could be due to dilution, dispersion, high mobility, adsorption, oxidation, hydrolysis and rapid precipitation. The concentrations of toxic metals such as Zn, Pb and Cu were higher in dry seasons than in wet seasons as a result of intense evaporation, association with sulphide minerals and their release during mining weathering and immobility in the case of Pb. Cadmium, Ni, and Fe concentrations were on the other hand higher in wet seasons than in dry seasons. This is because they were among metals not trapped in hard pan layers and thus readily released. Cadmium elevation may also be due to its association with Sphalerites which are weathered easily and dispersed. Iron (Fe) maybe as a result of co-precipitation among other factors while Pb is generally insoluble and immobile. From the study also, mean concentration of Fe in mg/l was 195.35 in dry soil and 321.89 in wet soil. Copper was 0.53 and 0.17, Zn 1.45 and 0.61, Pb 0.52 and 0.08, Ni 4.10 and 0.51 and Cd 0.55 and 1.48 in dry and wet season soils respetively. For sediment samples, the mean concentration of Fe was 608.03 and 164.12 mg/l in dry and wet season sediments respectively. Copper was 2.54 and 0.14, Zn was 2.81 and 0.54, Pb 0.56 and 0.06, Ni was 2.80 and 0.55 and Cd 0.79 and 1.12 in dry and wet season sediments respectively. In conclusion, the soil and sediment around Okaba coal mine have been polluted as a result of mining activities in both seasons. Seasonal metal variations were also observed for both media under investigation.

Publication Info:

Author: Ameh, E.G. , Idakwo, S.O. and Ojonimi, I.T.

Volume: 57

Issue: March

Published By: Journal of Mining and Geology, 2024-03-01