Author(s)

Kossitse Venyo Akpataku^1,2,3*, Masamaéya D. T. Gnazou¹, Gbandi Djanéyé-Boundjou¹, Limam Moctar Bawa¹, Serigne Faye²

¹Laboratory of Applied Hydrology and Environment, Faculty of Science, University of Lomé, Lomé, Togo.
²Department of Geology, Faculty of Sciences and Techniques, Cheikh Anta Diop University, Dakar, Senegal.
³Department of Chemistry, Faculty of Sciences and Techniques, University of Kara, Kara, Togo.

This study aimed to identify the role of natural and anthropogenic influence on geochemical processes controlling groundwater salinization in the middle portion of the Mono River basin, Togo. Multivariate statistical analysis, geochemical masse balance modeling, and conventional graphical methods were applied to the chemical dataset obtained from 110 groundwater samples collected during two campaigns (March-May 2011 and April 2014). The results showed that groundwater is predominantly fresh, acidic to circumneutral and mixed cations-HCO^-₃ water types. The proportion of ions (Na⁺, K⁺, Cl^- and SO^2-₄) occurring ubiquitously in a saline environment increases substantially with TDS. Two factors, defined as natural and anthropogenic, account for 76.5% of the hydrochemical dataset variance. Based on the hierarchical cluster analysis, groundwater samples are classified into four clusters that corroborate the factor analysis results and illustrate different hydrochemical evolution stages along a topographically-driven groundwater flow path. The primary natural process contributing to cations and bicarbonate ions is the weathering of silicate minerals and possibly secondary carbonates by infiltrating water enriched with soil CO₂ gas. Groundwater salinization indicators including Cl^-, SO^2-₄ and NO^-₃, originate from potential sources such as human and animal wastes, agrochemicals, and deforestation. Thermodynamic equilibrium conditions ranged from saturation to oversaturation with respect to quartz, chalcedony, amorphous silica, calcite, dolomite, sepiolite, and talc. In conjunction with the lowering of CO₂ partial pressure and evaporation, these conditions restrict acidic hydrolysis of primary silicates but magnify the groundwater salinization process in the lower elevation areas where soil crusts’ formation is favorable. This study showed the effective use of multivariate statistical analysis and complementary techniques in identifying the significant factors and processes controlling groundwater chemistry.

Mono River Basin, Groundwater, Silicates Weathering, Anthropogenic Contamination, Salinization, Togo

Akpataku, K. , Gnazou, M. , Djanéyé-Boundjou, G. , Bawa, L. and Faye, S. (2020) Role of Natural and Anthropogenic Influence on the Salinization of Groundwater from Basement Aquifers in the Middle Part of Mono River Basin, Togo. Journal of Environmental Protection, 11, 1030-1051. doi: 10.4236/jep.2020.1112065.