Pollution by Trace Metallic Elements in Groundwater around Lake Toho in Mono Department, Southern Benin

Abstract

This study aimed at assessing the level of contamination of groundwater around Lake Toho in Trace Metal Elements (TME) following two campaigns (one in the dry season and the other in the rainy season). A total of eleven (11) samples (two wells and nine boreholes) were analyzed by Spectrometry Microwave Plasma Atomic Emission (MP-AES). Measured parameters are Fe, Mn, Cu, Zn, Ni, Hg, Pb, Cd, As and Cr. Values obtained are compared with Benin and WHO recommendations for drinking water. It appears there are not Hg and Pb in waters during both seasons. Cu and Zn are non-existent in waters during the dry season but appear during the rainy season. Cd is absent in waters except in those of Vêha and Logbo which revealed it presence in the dry season, but disappeared in the rainy season. Such is also the behavior of As in the water of Goudohoué. Concentrations of Mn and Ni in dry season dropped in the rainy season. The waters of some sites revealed an increase in Cr in the rainy season compared to the dry season. Fe contents in all the waters increased in the rainy season compared to the dry season. The contamination factors as well as the degrees of contamination of water pollution were calculated and revealed a high contamination of waters in TME. This study shows that the groundwater around Lake Toho is under influence of anthropogenic activities that promote appearance of elements as Fe, Cr and Ni, representing health risks for populations.