Potential sources and evaluation of metal pollution of groundwater in the upper part of the Comoé Basin, Burkina Faso

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Résumé

Mining and agricultural practices pose groundwater pollution problems. This study assesses metallic pollution in groundwater in the Comoé Basin in Burkina Faso. 30 samples were collected during the dry season and 29 after the rains for analysis of Cr, Cu, Ni, As, Zn, Pb, and Cd by ICP-MS. The average concentrations of elements follow this order: Zn > Cr > As > Ni > Cu during the dry season and As > Zn > Cu > Cr > Ni > Pb > Cd during the rainy season. Concentrations of Zn, Cr, Ni, Cu, Pb, and Cd comply with standard limits. Arsenic levels vary from 0.03 to 23.47 µg/l during the dry season and from 0.03 to 458.21 µg/l during the rainy season. Gold mining is identified as the anthropogenic source that increases significantly groundwater pollution in Tiéfora commune additionally to its natural pollution. The Heavy Metal Pollution Index revealed 11 polluted water points during the dry season and one polluted point during the rainy season. According to the Heavy Metal Evaluation Index, the level of water pollution is low. The Water Pollution Index indicates that the water quality is excellent except for one point, P17, which is very poor quality. Regarding health risks, adults who stock up at P15 and P19 and children who stock up at these points and at P22 in the Tiéfora commune are exposed to non-carcinogenic effects. However, all consumers of P2, P5, and water points of Tiéfora are vulnerable to cancers linked to arsenic ingestion. Given the variability and levels of concentrations, it is important to monitor metal pollution in the groundwater.

Mots-clés

Comoé Basin, Groundwater, Pollution, Trace metals