Tracing potentially toxic elements and nutrient levels from extensive illegal mining using multivariate statistics, pollution indices and ecological assessments

Abstract

Mining activities have increased the levels of Potentially Toxic Elements (PTEs) PTEs contamination in soils, leading to major concern due to their potential risk. This study considered pollution levels of PTEs and their possible implications in an illegal mining site in southern Ghana during the ban on small-scale mining activities. Soil samples were also collected from residential and pristine areas as controls. Individual, complex and multi-elemental indices and exposure assessment were the assessment computations used. As, Hg, Pb, Sr and V had a significant relationship (0.05, χ² (4) = 50.61, p < 0.001). Multiple comparisons indicated substantial differences between the following variable pairs: Pb-As, Pb-Hg, As-Sr, As-V, Hg-Sr, and Hg-V. Nutrient levels were significantly differences (0.05, χ² (4) = 54.41, p < 0.001) with significant differences between N-K, N-Zn, N-Na, P-K, P-Na, K-Zn, and Zn-Na. The Robust Compositional Contamination Index (RCCI) analysis showed that the area was heavily impacted following 85 % of the samples ranging between high and highest pollution. A comparative assessment revealed that all the pollution indices followed a similar trend of pristine < residential < mining site, except for Mn and Sr where a pattern pristine > residential > mining with an elemental trend: Mn < V < Sr < Zn < Cu < As < Pb < Hg. The indirect and poor relations between EC and N (r = 0.19), P (r = 0.36), K (r = −0.58), Zn (r = 0.37), Na (r = −0.08) and Ca (r = −0.50) indicates that the mined site had a poor water-soluble capacity of plant uptake of some essential elements. Pollution levels follow a clear trend from pristine to residential to mining areas, with notable impacts on nutrient levels and plant uptake capacity. The analysis showed significant differences in elemental concentrations between illegally mined and pristine areas, with p-values of 0.001 for As, Cu, Hg, Mn, Pb, Sr, and Zn, and 0.003 for V, indicating that illegal mining has substantially elevated levels of these toxic metals. Immediate intervention and sustainable management are critical to address these environmental and ecological risks.