Characterization Of Sands For Heavy Minerals, Selected Heavy Metals Distribution And Profiling Along River Tiva, Kitui County, Southeastern Kenya

Abstract

The main objective of this study was to characterize the river Tiva sands for heavy mineral content. The study, in addition, has determined the elements associated with heavy minerals of interest; titanium (Ti), iron (Fe) and zirconium (Zr) in 47 samples that were randomly sampled from 10 site locations representing Kalimbevo, Nduumoni and Tanganyika at the surface and at the depth of 0.3 -0.5m. Sampling was done along river Tiva for a stretch of 3 Km along the river course between 3rd and 5th June, 2012. The sand samples were dried to constant weight, pulverized, sieved and pelletized before analysis by Energy Dispersive X-ray fluorescence (EDXRF). The sand samples were prepared in aliquots of triplicate pellets of a diameter of 2.5cm and weighed between 0.3-0.5g. The elemental determination was done using an Energy Dispersive X-ray Fluorescence spectrometer (EDXRF), Shimadzu (EDX 800HS) available at the Department of Materials and Testing Laboratories in the Ministry of Infrastructure and Transport. Each sample pellet was irradiated for the 50s. X-ray diffraction (XRD) analyses were done at ICRAF using Bruker, D2 Phaser spectrometer for mineral identification. Principal component analysis (PCA) was performed on the results of elemental concentrations to determine the correlation between the elements and the source of the heavy minerals. In general, this study found out that the mean values of; iron (Fe) to be 73135±6027μg/g, titanium (Ti) 22976±1971μg/g and zirconium (Zr) 1115±136μg/g. XRD results of analyses showed the existence of ilmenite and hematite as some of the heavy minerals present in these samples. Element Fe/Ti ratios were used to determine titanomagnetite properties, in addition to regression and principal component analysis (PCA) in determining the source of the elements. Results of EDXRF data obtained showed iron oxide (Fe2O3) to average 10.46%; titanium dioxide (TiO2) results average at 3.83% and that approximately 80% of the iron in these samples is confined to magnetite and a proportionate relationship between iron and titanium dioxide is indicative of significant titanomagnetite content described by PCA analysis of the results. iv The distribution of these elements was studied along the river, across, and at depths along the river Tiva profile. The results show that elemental concentration increases downstream except at convex of the river where there are elevated concentrations. In general, high elemental concentration was also found in the subsurface samples of the river bed than at the depth of the riverbed at 50cm. For example, the average Fe concentration at the subsurface is 104328μg/g compared to 51016μg/g at the depth of 50cm; a similar trend is replicated for Ti (34033μg/g against 14635μg/g) and zirconium (Zr) was found to be in low concentration (1529μg/g against 593μg/g). There is no statistical significant difference in the elemental concentration distribution across the river bed, following the ANOVA analyses. In conclusion, this study has demonstrated the potential existence of titanium bearing heavy minerals in river Tiva sands and recommends; Heavy mineral separation studies, Provenance studies, complementary characterization techniques for heavy minerals, interrelationship between river Tiva and Kwale heavy mineral sands and ilmenite alteration studies.