THERMODYNAMIC MODELLING OF THE EQUILIBRIA IN LAKE BARINGO, KENYA

Abstract

The equilibria that control the composition of a lake is presented using lake Baringo, Kenya, as an example. Lake Baringo (0°37’N, 36°05’E) lies very close to the equator in the Baringo basin in the Eastern Rift Valley, Kenya. Water from the lake was analysed chemically using standard analytical techniques to obtain the stoichiometric concentrations of the major anions and cations. However, this does not indicate how the components are distributed amongst possible species. The speciation calculation was performed using the available equililbrium constants for all the metal – ligand and proton – ligand species identified. At pH 8 the composition of the water of lake Baringo was Ca2+ (58.88%); CaCO3 (41.12%); Mg2+ (97.33%); MgCO3(2.88%); HCO3 - (98.27%) and SO4 2- (99.88%). Sulphate forms very weak complexes of calcium and magnesium and was excluded from the model. MgHCO3 + , CaHCO3 + and MgSO4 were found to be minor species.