Sources and pollution assessment of trace elements in soils of some selected mining areas of southwestern Ghana

Abstract

This study presents a detailed assessment of the soil quality of the Prestea-Huni Valley and Wassa areas which host a significant portion of Ghana’s mining industries. A total of 300 soil samples were collected across the districts. Zn (71%), Ni (54%), Mn (5%), Fe (46%), and Cr (50%) exceeded their respective guidelines. Similarly, 50%, 100%, 43%, and 98% of the soil samples were beyond acceptable limits for Co, Cu, As, and Ba respectively. Soils within the study areas had elevated concentrations of V, Cr, As, Ag, and Pb whereas Mn, Cu, Ni, Zn, Sr, and Co were in bearable concentrations. High levels of As and Pb could be attributed to the long-practiced​ mining activities and the application of inorganic fertilizers. Disparities were shown in the computed pollution indices due to various factors that affect their importance. Pollution indices may not be readily comparable. The factor analysis showed significant loadings of Ag, Ba, Cr, Cu, Fe, Ni, Pb, V, and Zn as they showed higher signals of the data and predominantly impacted the quality and variability of the soils. The Friedman rank-sum test showed significance: χ 2 (4) = 958.66, p < .001 for As, Pb, Zn, Cu, and Cr, χ 2 (4) = 1046.73, p < .001 for Ni, Mn, Fe, Co, and Ba, and χ 2 (2) = 448.62, p < .001 for V, Sr and Ag using an alpha value of 0.05. Elemental variations in the soils indicate that the factors influencing the accumulation of heavy metal(loid)s were by a range of factors. • Pollution indices are not scale-invariant and may present different elemental loads. • PTEs and heavy metal(loids) levels are on a rise in most of Ghana’s mining areas. • Non-mining areas are also prone to the deleterious impacts posed by PTEs and metal(loid)s.