Distribution, bioaccessibility and human health risks of toxic metals in peri-urban topsoils of the Kumasi Metropolis

Abstract

The occurrence of heavy metals in urban soils is of great environmental concern due to the unwanted health effect associated with their excessive exposure. The study assessed levels of heavy metals (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sn, V, and Zn) in peri-urban communities of the Kumasi metropolis and evaluated sources and potential health risk associated with exposure to these metals. Soil samples collected from topsoils at a depth of 0–10 cm were subjected to x-ray fluorescence (XRF) spectroscopy analysis for total metal quantification. The XRF results were then confirmed by inductively coupled plasma mass spectrometry. Soil pH, conductivity, and total organic carbon were determined using standard procedures. The mean concentrations (mg/kg) of metals were As (10.11), Cd (12.91), Cr (77.97), Cu (20.20), Fe (23031), Pb (18.60), Mn (158.68), Ni (29.33), Sn (8.83), V (78.21) and Zn (49.27). The pH and electrical conductivity were in a range of 6.5 - 8.5 and 153 - 8990 μS/cm respectively. The mean total organic carbon was 8.85%. Pollution indicators such as enrichment factor, contamination factor, and pollution load index all showed that soil in the study area is of low degree of contamination. The potential ecological risk index projected a low-risk effect. In contrast, the hazard index and carcinogenic risk index indicated no significant human health risk associated with exposure to the metals presently. However, to regulate bioaccumulation effects, constant monitoring is essential.