BENZENE DERIVATIVES AND SPECIATION OF SELECTED TRACE METALS IN LAKE BOGORIA GEOTHERMAL SYSTEM, KENYA AND HEAVY METAL ANALYSIS IN NYAMNYUMABA AND BUGARAMA HOT SPRINGS OF RWANDA

Abstract

Geothermal energy is a renewable and environmentally friendly resource that has gained traction in the recent past as an alternative source of energy to the fast-depleting fossil transport fuels. Nonetheless, research on the presence of trace metals and organic pollutants in geothermal water and steam is scarce in literature. This current study dealt with the examination of geochemical properties of geothermal springs in Lake Bogoria. During the analysis, quantification of poly alkyl benzenes was carried out using Gas Chromatography Mass Spectrometry (GC MS) and the results showed the presence of poly alkyl benzenes with a mean value of 0.37 ± 0.28 ppm, which is below the United States Environmental Protection Agency (US EPA) limit for most alkyl benzenes. Trace amounts of naphthalene were also detected in some samples. The trace metals – Mn, Cd, Pb, Cu and Ni were analysed using Atomic Absorption Spectroscopy (AAS). Statistical treatment of data was carried out using Pearson’s Correlation Coefficient (PCC), Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). The mean concentrations of Mn, Cu and Ni were found to be 0.19 + 0.08 ppm, 0.02 + 0.02 ppm and 0.03 + 0.02 ppm, respectively, values that are below the permissible World Health Organisation (WHO) limits. On the other hand, Pb and Cd showed mean concentrations of 0.06 + 0.04 and 0.05 + 0.02 ppm, correspondingly, values that are above the WHO limits. A related geochemical survey of Rwandan geothermal sites was also done, and it focused on investigating the presence of select trace metals (Pb, Cd, Mn, Ni and Cu) in Nyamyumba and Bugarama hot springs in the Western Province of Rwanda. The trace metals were determined using Micro Plasma Atomic Emission Spectroscopy (MP-AES). The mean concentrations of Cu in both Nyamyumba and Bugarama were found to be 0.1 ppm, which is within the permissible World Health Organisation (WHO) limits for potable water. Similarly, the concentrations of Mn were within the acceptable WHO limits with mean concentrations of 0.04 ± 0.02 and 0.11 ± 0.03 ppm in Nyamyumba and Bugarama, correspondingly. Lead was found to be beyond the WHO limits with mean results of 0.01 and 0.013 ± 0.01 ppm in Nyamyumba and Bugarama, respectively. Cadmium mean concentration was 0.01 ppm in both areas, which is above the permissible WHO limit. Nickel was below the detection limit. It is envisaged that the research findings of this study will enhance the scientific understanding of the geochemistry of the geothermal springs in the respective areas of study for their future efficient and sustainable exploitation as alternative green energy resources.