Comparative Assessment of Trace Metal Concentrations and Their Eco-Risk Analysis in Soils of the Vicinity of Roundhill Landfill, Southern Africa

摘要

Soil is a vital media in transmitting contaminants in the environment. Contamination of soils by trace metals has received much attention due to their associated toxicity, persistence, bioaccumulation and non-biodegradability that is harmful to the ecology. This study assayed the concentrations of trace metals in topsoils of the vicinity of Roundhill landfill using inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray fluorescence (XRF), compared the detection capabilities of the two techniques and determined ecological risks of the contaminants using geographical information system. Soils were collected from nine sampling sites around Roundhill landfill in the Eastern Cape and analysed for five trace metals using the two techniques. Mean concentrations of Cr, Cu, Ni and Zn determined by ICP-MS and XRF were normally distributed (p<0.05) from the parametric test while no significant differences between the two datasets were established from the non-parametric test. Under-estimated elemental concentrations determined by XRF were attributed to its high detection limits, matric effects, inter-elemental peak interferences and low sensitivity of the equipment. Correlation values of Cr, Cu and Ni showed a high degree of linearity compared to Pb. Evaluated eco-risk indices revealed low to extremely high ecological risks, posed by assessed trace elements in soils. Cr had the highest potency. Assayed trace metals were ecologically harmful to soils and their origin was linked to landfill leachate pollution.