Toxic Metals in Farmland Soils of Three Communities in Yenogoa Local Government Area: Concentrations and Impacts Assessment

Abstract

Sustainable agriculture is closely associated with farmland soils quality which is necessary for crops growth, and adequate supply of healthy foods. In this study, some toxic metals (Zn, Cu, Pb, Cd, Ni, & Cr) contents of soils in farmlands of three communities in Yenagoa LGA were evaluated. Analyses of soils samples were performed with Atomic Absorption Spectroscopy (AAS) after digestions with (5:1) mixtures of nitric and perchloric acids. The result reveals large variations in concentrations of metals in soils within and among the communities. However, the mean concentrations (mg/kg) of metals in the communities’ farm soils were: Zn (126.19±55.87), Cu (61.73±29.37), Pb (11.09±6.9), Cd (1.85±0.86), Ni (11.24±4.83), and Cr (2.56±1.53). The average sum of the six determined metals (∑6Metals) in the three communities in decreasing order was: Kpansia (244.71±54.05), Ikarama (205.61±48.28), Amarata (193.37±46.48). The overall average ∑6Metals for the communities was 214.66±50.21mg/kg. Evaluations using various indices reveals overall slight pollution by these metals with cadmium been the major driver of the pollution as reflected by its very high contamination factor. Zinc (Zn) and Cu showed moderate contamination factors, and their contributions to the overall pollutions were secondary. The other trio (Pb, Ni, & Cr) exhibited negligible impact on the overall pollutions due to their low contamination factors. The sequence of metals pollutions in the soils was: Cd > Cu ~ Zn > Pb > Ni > Cr. While the order of pollution in the communities was: Kpansia (KP) > Ikarama (IK) > Amarata (AM). The potential ecological risk index for individual metal (ER) were all low in all communities except for cadmium (Cd) which was very high in AM, extremely high in both KP and IK and thus impacting high risks values on the comprehensive potential ecological risk index (RI). These high levels of cadmium and the tendency of the metals to geo-accumulate in these soils overtime calls for measures to be put in place that will maintain levels that pose negligible human and ecological health risk.