Browsing by Author "Mohammed, Najat Kassim"

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    The optimalization of energy dispensive X-ray fluorescent (EDXFR) spectrometer for the study of heavy metals pollution
    (University of Dar es Salaam, 2000) Mohammed, Najat Kassim
    The study aimed to optimize and calibrate the EDXRF systm of the Physics Deprtment, University of Dar es salaam and then use it for the analysis of concentrations of heavy metals (Ti, Cr, Mn,Fe,Co, Cu, Zn, Rb, Sr,Y, Zr and Pb) in sediments, water hyacinth (Elchrornia Crassipes (Mart) solms,) and fish (Rastrinebola argentia0 from lake Victoria. The opi,al conditions ad detection limits were detrmined experimentally by variation of the excitation parameters. The optimal pair of voltage and current were found to be 40 KV an 30 MA and the optimal measuring time was found to be 2000 seconds. The study found that, the use of a collimator with two apertures of diameter 4 mm, placed 8 mm apart gives the best results. Heavy metals such as Ti,Cr,Mn, Fe, Co,, Cu, Zn, Rb, Sr, Y, Zr and Pb were found in samples of the sediments. In water hyacinth the heavy metals detected were Ti, Sc, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, sr, Y, Zr and Pb and the heavy metals detected in the samples of fish were Ti,, Sc, Cr, Mn, Fe, Cu, Zn. Rb, Sr and Pb. The conentrations of these elements in samples of sediments and water hyacinth collected at dometic and industrial areas are higher than that from non- industrial suburb area. They are also higher than the concentrations of sediments and water hyancinth reported elsewhere { Forester and Wittman, 2983, Ajmal et al, 1985, Ajmal et al, Gonzalez et al, 1989, Araujo et al, 1998}. This finding indicate that Lake Victoria is contaminated with heavy metals, which are mainly the by-products of industrial and domestic activities. The concentration of heavy metals found in fish samples ( Rastrinebola argentia ) from lake Victoria are higher than the concentrations reported for fishes from highly contaminated sites. However, the results show that, there is a positive correlation between the concentrations of Ti, Mn, Fe, Zn, Zr, and Pb found in sediments and in water hyacinth.