Browsing by Author "Koleleni, Yusuf I. A."

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    Aerosol Study Using Energy Dispersive X-ray Fluorescence Analysis
    (1989) Koleleni, Yusuf I. A.
    An Energy Dispersive X-ray Fluorescence Analysis (EDXRFA) system for quantification of thin aerosol samples is described. The detection limit is in the range of 10μ/sq. cm for thin samples and the precision is in the range of 1 to 8%. The spectrometer was used to study thin aerosol samples collected along the road site to assess pollution contribution due to exhaust and dust particles. The results are in good agreement with other techniques namely Particle Induced X-Ray Emission (PIXE), Neutron Activation Analysis (NAA) and Atomic Absorption Spectroscopy (AAS)
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    Air Pollution Studies of the Highest point of the Dar es Salaam City by X-Ray Fluorescence Analysis
    (1998) Koleleni, Yusuf I. A.
    A survey of the environmental pollutants in the city of Dar es Salaam was conducted. Aerosol sampling was conducted using a Sierra Anderson two way impactor for particles less and greater than 10 microns. Analysis was possible with X-ray fluorescence (XRF) rube excitation. We explore the analytical parameters of the spectrometer and present aerosol results for the months of January and February 1993/94 for cites at the highest points of the Dar es Salaam. The results have local significance but are also compared to international values. Lead values is of the order of 0.004 mg/L for Dar es Salaam (DSM) while World health Organisation (WHO), United States of America (USA), Canada and European Economic Community (EEC) values stands at 0.005 mg/L.
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    Analysis of Heavy Metals in the Shellfish from the Neighbourhood of the Sea Port of Zanzibar
    (2016-03) Koleleni, Yusuf I. A.; Haji, O. O.
    Shellfish is one of the major sources of food for coastal population of Zanzibar. Toxicity of shell fish by heavy metals is of concern to consumers. This study aimed at assessing the metal concentrations of the shellfish along the coast in the neighbourhood of Sea Port of Zanzibar. Shellfish (namely oysters, mussels, clams and crabs) were collected for the assessment on effects of heavy metal contamination among the aquatic organisms. The concentrations of the shellfish were determined using Energy Dispersive X-ray Fluorescence (EDXRF). The concentrations analysed include Cr, Mn, Fe, Ni, Cu, Zn, Cd and As. The range ofCd, Cr, Ni, Mn and Zn were found to be higher in clams while Fe, Pb and Cu were found to be higher in crabs. The values of Cr, Cu, Zn, As and shellfish species appear to be higher than the values reported in the literature.
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    Analysis of Rock-Geological Material from Places in Tanzania by Wavelength Dispersive X-ray Fluorescence Spectrometer
    (2009) Koleleni, Yusuf I. A.
    A number of precious stones and minerals in Tanzania are found either just on the ground surface or unexplored inside the earth. Principally, those found at the surface differ in their source of origin from those found inside the earth. Some of these stones are coming from the rocks in their present locations (primary deposits) while others are transported from other places (secondary deposits). The mechanism of transportation may be rivers, sea or wind. The distribution of these valuable stones is geographically irregular in Tanzania and in some of the regions the deposits are higher compared than others. In several parts of the country such information is completely unavailable and in many cases unexplored. In order to provide this information to the decision makers and investors, Wavelength Dispersive X-ray Fluorescence (WDXRF) Analysis has been used with objective of identifying the composition of some of these stone and rock samples. The samples identified and reported in this paper include: Iron ore, Green Aventurine, Amethyst, Red Garnet, Sapphire nuts, Green Opal, Blue Kymete, Black Tormaline, White opal, Aquamarine and Granite. The samples were prepared as pellets after mixing with boric acid or fused as discs for analysis. Typical results for the Iron Ore in % are SiO2 (0.97), Al2O3 (0.57), Fe2O3 (77.5), MnO (0.35), MgO (0.35), CaO (0.16), Na2O (< 0.01), K2O (0.04), TiO2 (19.1), P2O5 (< 0.01), SO3 (0.14) and that of the Amethyst SiO2 (97.8), Al2O3 (0.11), Fe2O3 (1.37), MnO (< 001), MgO (< 0.01), CaO (< 0.01), Na2O (< 0.01), K2O (< 0.01), SO3 (0.33). The results show that Tanzania is a very rich country in minerals but are currently unexplored either because of lack of information or investment capital.
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    Comparison of Room Scatter Factors Using Diodes and an Ion Chamber by Multiple Distance Method and A Kerma Rate Determination
    (2016-04) Jumaa, Dachi K.; Koleleni, Yusuf I. A.
    At ORCI, the Co-60 source with two gamma rays having energies of 1.17 MeV and 1.33 MeV which are is used for treatment of cancer of gynaecological malignancies in the HDR brachytherapy unit. The Room Scatter Factor, Kscatter suitable to a treatment room must be known before determination of reference air Kerma rate. This is because K the geometry set up of the source to chamber and immediate environment (IAEA, TECDOC1274, Faiz 2010). The 60Co source with an 2.0 Ci was installed in the treatment unit at the ORCI. The room scatter factor need to be known in order to determine reference Air Kerma Strength, . The objective of this study was to determine room scatter factor suitable for Ocean Road Cancer Institute (ORCI) High Dose Rate (HDR) Brachytherapy room and is reported in this paper.
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    Determination of Concentration of Heavy Metals in Fish from Sea Port of Zanzibar by Energy Dispersive X-Ray Fluorescence (EDXRF)
    (2015-05) Koleleni, Yusuf I. A.; Haji, Othman O.
    Seafood is the major source of food for a large number of people residing in the coastal areas of Zanzibar. It has been reported that the seafood are a connecting link for the transfer of toxic heavy metals in human beings. The present study assessed the metal concentration upon sample species of fish along the coast Sea Port of Zanzibar. Fish samples (namely changu, sardine, baracout and tuna fish) were the ideal species for the assessment study on effects of heavy metal contamination in aquatic organisms. They were collected at the Sea Port and the concentrations of the assessed metals were determined using Energy Dispersive X-ray Fluorescence (EDXRF). Concentrations of Fe, Pb, Cr, Ni, As, Cu and Zn were found to be higher in sardine whilst Hg was found to be higher in changu specie. Concentrations of Cd and Mn were found to be below the detection limits in all sample species but higher in mussels. Whereas Hg was only detected in changu species. Comparing the data from this study to data from other studies in other regions, the concentrations of Fe, Cr and As in different species of fishes collected was quite higher than the values reported in the literature. The results of this study indicated that As, Hg and Cr were higher in fish than WHO/FAO (2004).
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    Elemental Composition of Vegetables in the Dar es Salaam Market Using Wavelength Dispersive X-Ray Fluorescence Analysis
    (2016-01) Koleleni, Yusuf I. A.
    Concentrations of several elements were determined in vegetables collected from the Dar es Salaam City markets by Wavelength Dispersive X-ray Fluorescence Spectrometry (WDXRF). The method involved taking 1g of dried and finely grinded vegetables prepared as pellets for analysis. Vegetables analyzed belong to species of Vigina Unguiculata (Kunde), Amarathus (African Spinach), Cucuta maxima (Pumpkin), and Brassica Chinese (Spinach). The WDXRF SRS 300 with Rh anode was operated at 60kV, 5mA and 60kV, 50mA for different range of elemental analysis. In all the vegetable samples carbon and oxygen were found to dominate with high concentrations between 32% and 47%. This paper presents results for elemental concentrations in vegetables that are main meal of any average Dar es Salaam city resident.
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    Environmental Air Degradation in Dar es Salaam by X-Ray Fluorescence
    (Taylor and Francis, 2002) Koleleni, Yusuf I. A.
    In Dar es Salaam a study of the aerosol contents was conducted and particulate matter on the filters were collected using an AndersenTM PM10 impactor to determine the environmental air pollution. The contents were determined by X-ray fluorescence analysis. In this study sources of environmental degradation and the concentrations were named as follows: Combustion processes with range of Br from 10 to 800 ng/m3, Pb from 30 to 790 ng/m3. Industrial processes with range of Fe from 37 to 883 ng/m3, Cu from 14 to 310 ng/m3, Zn from 6 to 820 ng/m3. Top soil activities with range of K from 20 to 540 ng/m3, Ca from 24 to 3805 ng/m3, Ti from 2 to 59 ng/m3, Mn from 10 to 386 ng/m3. Marine processes with range of Cl from 20 to 310 ng/m3, S from 72 to 134 ng/m3.
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    Levels of Aerosol in Dar Es Salaam, Tanzania, Compared to Some Cities
    (2003) Koleleni, Yusuf I. A.
    The aerosol concentrations in the city of Dar es Salaam were found with aim of investigating pollution levels. The aerosol samples were collected on the sites of Tanzania Oxygen Limited (TOL) which is purely an industrial area, Ocean Road Cancer Research Institute (ORCRI) located along the sea shore at the port exit, and Dar es Salaam International Airport (DIA) far from the city center. The PM10 dichotomous impactor was used for sample collection. The analysis of the samples was conducted with x-ray fluorescence spectrometer. The values obtained for Dar es Salaam aerosol samples are compared to similar samples of aerosol data available for the cities of Kinshasa and Butare in the republic of Congo and Rwanda respectively. The elements found in the aerosol samples include Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Br, Rb, Sr, Zr, Pb and Se. The variations of the minimum and maximum values of the elemental concentration in the sample for these elements are given for the months between September 1996 and May 1997. The elemental variation was affected by seasonal weather parameters like rain, wind speed and their directions. Temperatures varied between 29 and 32°C; rainfall between 5 and 70 mm while wind speed varied between 5 and 20 m/s.
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    Suitable Filters for Analysis in Energy Dispersive X-Ray Fluorescence Spectrometry
    (1990) Koleleni, Yusuf I. A.
    Energy dispersive x-ray fluorescence is applied in the analysis of teflon and quartz filter material. We report on impurities observed using the two techniques and filters. These techniques have been used to analyse the concentration of a number of elements including Pb and Br and the results of the two methods give excellent agreement
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    X-Ray Fluorescence Analysis with Applications to Environmental Pollution
    (2007) Koleleni, Yusuf I. A.
    In the experiment with Energy Dispersive X-ray Fluorescence (EDXRF) and the Total Reflection X-ray Fluorescence (TXRF) analysis, the x-ray from the tube in a either secondary target or total reflection mode is used in to excite the sample. In the de-excitation process characteristic x-rays from the sample are detected by a semiconductor Si (Li) detector. Using the pre-amplifier and associated electronics, signals from different energy x-rays are arranged in ascending energy order in the multi-channel analyzer. The peaks have facilitated the identification of elements in the sample and their concentrations. In this paper the description of the experiments are given and samples such as aerosol, serum and water are given as typical examples. In making such analysis achievement can be made on safety of the air we breath, the food we eat and the water we drink from pollution and contamination
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    X-ray Fluorescence Spectrometry in Dar es Salaam
    (2006) Koleleni, Yusuf I. A.; Kondoro, John W.
    Energy-dispersive x-ray fluorescence (EDXRF) analysis has been established at the University of Dar es Salaam, Faculty of Science, Department of Physics. Calibration was conducted using thin films from Micromatter (USA) for secondary target XRF. We report on the performance of the spectrometer including the detection limits attained, which range from 0.01 to 10 ng cm−2 using collimators of 6 and 8 mm diameter under excitation conditions of 50 kV, 35 mA. The accuracy of the measurements was checked using IAEA SOIL-7 and NIST 3087a Certified Reference Materials. The experimental values differed by <5% from the certified values. The total reflection x-ray fluorescence (TXRF) facility added as a module to the existing XRF system provides detection limits between 0.1 and 100 pg for most of the elements measured