Heavy Metal Pollution Index of Surface Water and Groundwater Around Tongon Mine (Côte d’Ivoire)

Abstract

Water is a valued resource, which is increasingly being threatened by mining activity. Monitoring of surface water and groundwater quality around gold mine is essential in terms of heavy metals and toxic substances. The northern zone of Cote d’Ivoire where located Tongon is a highly mineralised zone, with extensive mining of gold. The quality of water resources in this region may be affected by the activity of the Tongon mine, which is the main gold mine in the region. The objectives of this study were to determine the concentration of heavy metals and the Heavy Metal Pollution Index (HPI) in surface water and groundwater around Tongon mine. The concentrations of As, Zn, Pb, Cd, Cr, Cu, and Mn have been evaluated at 21 surface water and 16 groundwater sampling stations. The concentration of these metals were analysed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for heavy metal pollution indexing. The concentrations of As, Pb, Cr, Cu and Mn in surface water were found to be above the highest desirable limit of WHO drinking water standard with mean concentrations of 5.761, 0.016, 0.178, 2.939, and 0.684 mg/L, respectively. Excepted As (2.95 mg/L) and Mn (0.67 mg/L), the metal concentrations in groundwater were well below the permissible limits of WHO drinking water standard. The Heavy Metal Pollution Index was used to evaluate surface water and groundwater quality. The results showed that, in the groundwater samples, HPI values (48.56-72.49) were less than 100, indicating a low-level heavy metal. Concerning surface water, HPI values of Poungbe River are well below the index limit of 100, which suggest that it is generally no contaminated with respect to these metals. The mining activity of Tongon is carried out while protecting water quality against heavy metals. The quality of water resources in the area must be regularly monitored to avoid any dramatic situation.