Origin of Mineralization of Groundwater in the Tongo Bassa

Origin of Mineralization of Groundwater in the Tongo Bassa

The Tongo Bassa watershed is located in the Douala sedimentary basin with the equatorial humid (4000 mm/year) type climate. The groundwater is weakly to strongly mineralized with values of conductivity less than 1450 μS/cm. The water type that predominates in the study area is Na-Cl type during both seasons. The mineralization of the resource is more accentuated in the dry season than in wet season following the reduction of the water Table due to low precipitation, over-exploitation and high temperature. Factor analysis was used to identify components (factors) which could explain the chemical characteristics of the aquifer. After rotation, three components could explain 84% of all the identified variables. The first component accounts for 61% of the variance and shows a high positive correlation of electric conductivity with Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^-, SO₂^4-, Br^-, NH⁴⁺ and HCO^3-. This component can be attributed to leaching of surface salts in soils as well as basic trading mechanisms. The second component is responsible for 13% of the variance. It is positively correlated with NO3 -, and negatively with pH. This is due to the nitrification of organic matter present on the ground. The third component was positively correlated with F^- , resulting from the dissolution of micas and representing 9.8% of the variance. The application of exploratory multivariate method identified the most relevant parameters that explain the mineralization of the water.