Trace Metals Migration and Contamination Assessment of Groundwater in the Lower Volta River Basin, Ghana

Abstract

This study was conducted to assess the migration of trace metals (TMs), their sources and potential human health risks in the Lower Volta River Basin (LVRB) of Ghana using preference technique, geometrical analysis, hydrochemistry, TMs evaluation index, correlation matrix and USEPA risk assessment model. Results of enrichment evaluation and geometrical analysis revealed that Fe, Mn, Pb and Ni are the dominant TMs within the unsaturated zone. Moderate vertical migration trends of Pb and Ni in agreement with hydraulic conductivity and Cl− were also displayed. The distribution of the TMs on Ficklin diagram suggests that their dissolution is less depended on the groundwater acidic environments. The mean dominance of the TMs in the groundwater follows the order of Fe > Mn > Ni > Cu > Pb > Zn. Results of TM evaluation index showed that 37%, 57% and 6% of the groundwater are of low, medium and high pollution categories. The hydrochemistry, correlation, biplots and three-dimensional plot jointly revealed that Pb, Ni and Mn occurred in the groundwater as migrating constituents of effluents and agricultural inflows. Also, hydrogeochemical conditions favour vertical migration of Fe. Results of non-carcinogenic risk quotients showed that 6%, 9%, 43% and 100 of the groundwater were above unity for Fe, Mn, Ni and Pb. Hazard index values were > 1 for all human categories. Pb and Ni showed high potential non-carcinogenic risk. Also, Ni showed greater cancer risk for all age groups. The study is key to preventing groundwater quality depletion in the basin.