Geochemical distribution, statistical and health risk assessment of toxic elements in groundwater from a typical mining district in Nigeria

Abstract

Globally, the influence of mining activities on the quality of drinking waters have been reported by several researchers. Long-term exposure to potentially toxic elements (PTEs) (e.g. As, Cd, Co, Cu, Fe, Mn, Ni, Pb, Se and Zn) can cause serious health hazards to consumers of polluted water. In the current study, twenty groundwater samples from Ameka mine area were analyzed for PTEs pollution and the associated human health risks. The concentrations of As, Cd, Ni, Pb Co, and Se were found to be above their standard limits in majority of the samples. Index methods such as heavy metal evaluation index, heavy metal pollution index and contamination degree confirmed that majority of the samples are loaded with PTEs. Similarly, synthetic pollution index further revealed that all the samples are extremely polluted and thus very unsuitable for human consumption. The health risk assessment model proposed by US-EPA was applied in assessing the associated health risks of PTEs in the groundwater resources. Non-carcinogenic health risk assessment predicted that 100% of the samples have hazard index values > 4, indicating an extremely high chronic health risk for adults and children. Similarly, carcinogenic risk assessment showed that all the samples pose high cancer risk to both populations due to As, Ni and Cd pollution. However, all the samples pose low cancer risk due to Pb enrichment. Multivariate statistical analyses (such as Pearson’s correlation matrix and principal component extractions) indicated that mining activities and rock-water interactions (weathering) are the responsible sources for the elemental pollution of the groundwater system. Before consumption, adequate treatment is recommended for the polluted waters.