Research Repository :: Browsing by Author "Mohammed, Najat K."

Browsing by Author "Mohammed, Najat K."

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ASSESSMENT OF HEAVY METAL AND RADIOACTIVITY LEVELS IN SPINACH (Spinacia oleracea) GROWN AT BAHI WETLANDS IN DODOMA REGION
(College of Natural and Applied Sciences, 2018) Mohammed, Najat K.; Haule, Boniface
This study reports on the levels of heavy metals and radionuclides in Spinach (Spinacia oleracea) grown in Bahi wetlands in Dodoma Region. The farm soil in Bahi wetland has been reported to contain elevated concentrations of 238U, 232Th and 40K due to the existence of shallow uranium deposit in the area. In this study, spinach (Spinacia oleracea) grown in three zones of Bahi district were analyzed for heavy metals and radioactivity associated with the uranium deposit in the area. The concentrations of elements were determined by Energy Dispersive X-ray Analysis (EDXRF) of Tanzania Atomic Energy Commission, Arusha. The activities of the radionuclides were calculated from their concentration in μg/g. The concentrations of Pb and Cd in all samples were found to be higher than the maximum tolerable limits recommended by Codex 2015. The results show that, the mean activities of 232Th (10.8 Bq/kg) and 40K(686.9 Bq/kg)in the samples are lower than the maximum tolerable limits (1000 Bq/kg) recommended by WHO/FAO, yet higher than their activities in samples of spinach collect from a control area. Hence, regular monitoring of heavy metals and radioactivity level in farm soils and agricultural products is recommended.
ASSESSMENT OF HEAVY METAL CONCENTRATION IN WATER AROUND THE PROPOSED MKUJU RIVER URANIUM PROJECT IN
(College of Natural and Applied Sciences, 2015) Banzi, Firmi B.; Msaki, Peter K.; Mohammed, Najat K.
Effective verification for compliance with water quality standards in uranium mining in Tanzania requires data sensitive to monitor heavy metal concentration in water around the Mkuju River Uranium Project before mining commences. The area susceptible for pollution by the project was estimated using AERMOD dispersion model and found to cover about 1300 km2. Thirty one surface and groundwater samples were collected and analysed for heavy metals and physicochemical properties using ICP-MS and standards techniques, respectively. The physicochemical properties for water samples analysed ranges from 5.7 to 7.8 for pH, 2.8 to 80.2 mg/L for TDS and 15 to 534.5 mS/cm for EC. These values show that the water in the vicinity of the Mkuju River Uranium Project is normal. The ranges of concentration of heavy metals (μgL-1) determined in water ranges were: Al(2 to 9049), Cr(0.2 to 19.96), Mn (0.1 to 1452),Fe(2 to 53890),Co(0.02 to 27.63), Ni(0.2 to 9.7), Cu(2 to 17), Zn(2 to 62.94), As(0.4 to 19.17), Cd(0.02 to 0.14), Pb (0.02 to 78.68), Th (0.002 to 1.73),U(0.002 to 29.76). These values are below the tolerance levels of concentrations set by different International organisations. Therefore heavy metal toxicity in the study area is marginal. The parameters that could serve as baseline data because of their enhanced sensitivity to pollution were (i) concentration of chromium, cobalt, nickel, copper, zinc, arsenic, cadmium and lead in water (ii) pH, TDS and EC for water, (iii) TDS ratio for surface to ground water values and (iv) correlation coefficients between the heavy metals. However, since TDS values are season dependent, this indicator can serve as baseline data when measured during the dry season as was the case in the study.
Assessment of Heavy Metal Concentration in Water around the Proposed Mkuju River Uranium Project in Tanzania
(2015) Banzi, Firmi B.; Msaki, Peter K.; Mohammed, Najat K.
Effective verification for compliance with water quality standards in uranium mining in Tanzania requires data sensitive to monitor heavy metal concentration in water around the Mkuju River Uranium Project before mining commences. The area susceptible for pollution by the project was estimated using AERMOD dispersion model and found to cover about 1300 km2 . Thirty one surface and groundwater samples were collected and analysed for heavy metals and physicochemical properties using ICP-MS and standards techniques, respectively. The physicochemical properties for water samples analysed ranges from 5.7 to 7.8 for pH, 2.8 to 80.2 mg/L for TDS and 15 to 534.5 mS/cm for EC. These values show that the water in the vicinity of the Mkuju River Uranium Project is normal. The ranges of concentration of heavy metals (µgL-1 ) determined in water ranges were: Al(2 to 9049), Cr(0.2 to 19.96), Mn (0.1 to 1452),Fe(2 to 53890),Co(0.02 to 27.63), Ni(0.2 to 9.7), Cu(2 to 17), Zn(2 to 62.94), As(0.4 to 19.17), Cd(0.02 to 0.14), Pb (0.02 to 78.68), Th (0.002 to 1.73),U(0.002 to 29.76). These values are below the tolerance levels of concentrations set by different International organisations. Therefore heavy metal toxicity in the study area is marginal. The parameters that could serve as baseline data because of their enhanced sensitivity to pollution were (i) concentration of chromium, cobalt, nickel, copper, zinc, arsenic, cadmium and lead in water (ii) pH, TDS and EC for water, (iii) TDS ratio for surface to ground water values and (iv) correlation coefficients between the heavy metals. However, since TDS values are season dependent, this indicator can serve as baseline data when measured during the dry season as was the case in the study.
Assessment of heavy metal contamination in vegetables consumed in Zanzibars
(Scientific Research, 2012-01) Mohammed, Najat K.; Khamis, Fatma
Samples of amaranth and cabbage from Zanzibar were analyzed for heavy metal concentrations using Energy Dispersive X-ray Fluorescence spectrometry (EDXRF) of Tanzania Atomic Energy Commission (TAEC) in Arusha. Thirty samples of amaranth and twenty five samples of cabbage were collected from four farms and two markets at Urban West Region in Zanzibar. The concentrations of Al, Cl, Cr, Mn, Fe, Ni, Zn, Cu, Ag, I, Br, Cd and Pb are presented and discussed. Amaranth had significant (P < 0.05) higher concentrations of Zn, Fe, Cr and Mn than cabbage, whilst Cd, Ni and Pb were significantly (P < 0.05) higher in cabbage than amaranth. Although the mean concentrations of the essential elements were in the range reported in literature, Pb and Cd were in concentrations above FAO/ WHO maximum tolerable limits.
Assessment of Natural Radioactivity in Soil and its Contribution to Population Exposure in the Vicinity of Mkuju River Uranium Project in Tanzania
(Science Technol, 2016) Banzi, Firmi B.; Msaki, Peter K.; Mohammed, Najat K.
The level of 226Ra, 232Th and 40K was established in soil collected in an area about 1,300 km2 in the vicinity of Mkuju uranium project in Tanzania and selected points in the concession using HPGe spectrometer and associated exposure risks to population were estimated. The radioactivity concentration in the vicinity range (Bqkg-1) for 226Ra (24.94 to 53.50), 232Th (20.86 to 47.14), and 40K (344.50 to 697.54). Whereas, radioactivity in the concession range for 226Ra (2430.00 to 4200.00), 232Th (130.00 to 220.00), and 40K (1293.30 to 1466.10). On average the radioactivity in the concession were about 89, 5 and 3 times high than those in the vicinity. Based on the measurements, the hazards attributable to use of soil from the vicinity for different purposes is marginal. However, the hazards indices indicate that soils from the concession have relatively a significantly risk by range of factors about 27 to 29 and 40 to 42 times high than in the vicinity for the external and internal hazards, respectively. Also the radium equivalent radioactivity, dose rate and effective dose tend to be significantly high in the concession than in the vicinity by range of factors from 27 to 29, 23 to 25 and 23 to 25, respectively. These findings reveals that soils in the vicinity of the project could pose less radiological risk to human health when compared to soil in the concession.
ASSESSMENT OF RADIOACTIVITY LEVELS IN COAL AND COAL ASH IN KIWIRA COAL MINE USING GAMMA-RAY SPECTROMETRY
(College of Natural and Applied Sciences, 2018) Makundi, Ismael N.; Nyaki, Mungubariki M; Mohammed, Najat K.
This study aimed to assess the radioactivity levels and associated dose rates from the naturally occurring radionuclides 226Ra, 232Th and 40K in coal and coal ashes at Kiwira coal mine. The radioactivity of 40 representative coal, fly ash samples were measured using gamma spectroscopy of the Tanzania Atomic Energy Commission (TAEC) in Arusha, Tanzania. The activity concentrations of 226Ra, 232Th and 40K in coal and coal ashes from Kiwira were higher by several orders of magnitude than their worldwide average values. The calculated radium equivalent activity, the air absorbed dose rate, external hazard index and the average annual effective dose rate in fly ashes were 1335 ± 60 Bq kg-1, 610 ± 29 nGy h-1, 4 ± 0.4, 738 ± 52 μSv y-1 which were higher than the international recommended values of 370 Bq kg-1, 57 nGy h-1, and 70 μSv y-1 for fly-ashes respectively. The results provide information for the radiation protection when the coal and its by-products in the vicinity of Kiwira coal field is used. The data can be used by the authorities to design an appropriate method for handling wastes and implement intervention measures to protect the miners, the public as well as the environment.
ASSESSMENT OF RADIOACTIVITY OF 226Ra, 232Th AND 40K IN SOIL AND PLANTS FOR ESTIMATION OF TRANSFER FACTORS AND EFFECTIVE DOSE AROUND MKUJU RIVER PROJECT, TANZANIA
(2017) Banzi, Firmi B.; Msaki, Peter K.; Mohammed, Najat K.
Purpose. To establish pre-mining indicators to assess radiological impact as a result of release of radionuclides to environment during uranium mining at Mkuju River Project radioactivity of 226Ra, 232Th and 40K in soil, plants, fruits and cereals. Methods. The High Purity Germanium detector was used to determine the radioactivity and the data were subsequently used to establish soil to plant transfer factors and annual effective dose. Findings. The results revealed a strong positive correlation (r) of 0.947 and 0.950 for 226Ra and 232Th, respectively, between values determined in soils and plants. Implicit in these finding is that the distribution of radionuclides in soils is directly proportional to the corresponding radionuclides in plants. Originality. The roots of wild grass had the highest specific radioactivity (Bqkg-1) for 226Ra (2.15 ± 0.02), 232Th (1.43 ± 0.02) and 40K (198.16 ± 1.72) and the roots of cabbage had the highest values for 226Ra (1.38 ± 0.04), 232Th (1.34 ± 0.03) and 40K (146.12 ± 1.02) among the food crops, an indication of a higher ability to uptake radionuclides from soil. Similarly, since the TFs were found higher in wild grass for 226Ra (0.0533 ± 0.04), 232Th (0.0374 ± 0.002) and 40K (0.5297 ± 0.05) and cabbage for 226Ra (0.0362 ± 0.03), 232Th (0.0360 ± 0.001) and 40K (0.4173 ± 0.05). Practical implications. It is an evident that these plants can serve as good bio indicators to assess release of radionuclides from inside the mining site to the public domain. Moreover, the annual effective dose (mSvy-1) for 40K (0.23 ± 0.02), 226Ra (0.046±0.004) and 232Th (0.073 ± 0.006) in edible crops when consumed in the vicinity of the MRP before the mining operations were, as expected, insignificant.
ASSESSMENT OF THE ESSENTIAL AND TOXIC ELEMENTS IN COMPLEMENTARY FOODS FOR UNDER FIVE CHILDREN IN TANZANIA USING EDXRF SPECTROSCOPY
(College of Natural and Applied Sciences, 2016) Paschal, Catherine; Mohammed, Najat K.
In this study, the commonly used complementary foods (Unga wa Lishe) for children 0-5 years in Tanzania were analyze for essential and toxic elements in order to assess their nutritional levels. 60 samples were purchased from shops in Dar es Salaam, Moshi and Arusha regions and analyzed using Energy Dispersive X-Ray Fluorescence Spectroscopy (EDXRF). The concentrations of the essential elements were referenced to the Recommended Nutrient Intake (RNI) values for 6-12 months old children while the levels of toxic elements were compared to the Maximum Tolerable Limits (MTL) set by WHO 2004. The nutrient intake for Fe, Zn, Cu and Ca obtained in the complementary foods were less than the RNI values of 11.6 mg/day, 8.3 mg/day, 0.56 mg/day and 500 mg/day respectively set by Joint FAO/WHO and Codex. On the other hand, the concentrations of the toxic elements Ni and As were higher than the MTL (0.2 μg/g and 11 μg/g, respectively) for these elements recommended by EC and WHO 2004, respectively. Further analysis of the complementary foods in Tanzanian is needed to produce more data which will be a guide for the appropriate measures to reduce mineral malnutrition in Tanzania.
Assessment of the Lake Gendabi salt for trace elements and toxic heavy metals by energy dispersive X-ray fluorescence spectrometry
(Springer Netherlands, 2012-08) Lugendo, Innocent; Mohammed, Najat K.; Mussa, L. M.; Spyrou, Nicholas M.
This study has analyzed samples of salts from Lake Gendabi, located in the northern part of Tanzania for metal contamination using the EDXRF spectrometry. The aim of the study was to assess the suitability of the salt from Lake Gendabi for human consumption. Seventy-five samples of salt were collected from the Lake Gendabi floor and grouped into five grades (G1, G2, G3, G4 and G5) depending on the position of the salt from the lake shore. In addition to Na and Cl, concentrations of 17 more elements were determined in all five grades of salt. These included seven toxic metals which are Al, Ni, Cr, Cd, Pb as well as Th and U which are both toxic and radioactive. The concentrations of all toxic elements found in the samples were higher than their Maximum tolerable limits set by international organizations. As this salt is used in many parts of Tanzania, it is proposed that the salt should be thoroughly purified before entering the market. Further research to include salt samples from other salt production areas in Tanzania is recommended.
Challenging Issues in Regulating Uranium Mining in Tanzania
(Springer International Publishing, 2014-09) Banzi, Firmi B.; Msaki, Peter; Mohammed, Najat K.
Experiences have shown that unregulated uranium mining practices have led to significant radiological risk to workers, public and the environment. Tanzania is about to start uranium mining in different parts of the country. Although the legislation and regulations to control doses to workers, public and the environment are in place, there are challenges to adequately address best practice requirements during and after the mining operations. This paper provides an overview of the challenges in addressing the regulatory compliance
Concentration Levels and the Associated Health Risks of Elements in Food Crops Grown in the Neighbourhood of Minjingu Phosphate Mine, Tanzania
(SCIENCEDOMAIN international, 2017) Mohammed, Najat K.; Nkuba, Leonid L.
The concentration levels of heavy metals in food crops (maize and mung beans) grown in the neighbourhood of Minjingu Phosphate mine were analyzed using EDXRF. The metal concentrations in both food crops followed the following pattern Fe > Zn > Cu > Cd > Cr > Pb > As. Maize accumulated higher levels of all analyzed elements than mung beans. The concentration level of metals in maize and mung beans from Minjingu were higher than those from the control site. Except for Cd in both types of samples, the concentration levels of all other metals were below the FAO/WHO recommended limits. The risk assessment showed that consumption of mug beans from Minjingu is without any safety risk while there is a risk in consumption of maize due to the concentration of Cd. However, the number of samples was not sufficient enough to make a definite conclusion; therefore, there is need for further analysis to include more data.
Determination of essential and toxic elements in clay soil commonly consumed by pregnant women in Tanzania
(Elsevier, 2013-10) Mwalongo, Dennis A.; Mohammed, Najat K.
A habit of eating clay soil especially among pregnant women is a common practice in Tanzania. This practice known as geophagy might introduce toxic elements in the consumer's body to endanger the health of the mother and her child. Therefore it is very important to have information on the elemental composition of the eaten soil so as to assess the safety nature of the habit. In this study 100 samples of clay soil, which were reported to be originating from five regions in Tanzania and are consumed by pregnant women were analyzed to determine their levels of essential and toxic elements. The analysis was carried out using energy dispersive X-ray fluorescent technique (EDXRF) of Tanzania Atomic Energy Commission, Arusha. Essential elements Fe, Zn, Cu, Se and Mn and toxic elements As, Pb, Co, Ni, U and Th were detected in concentrations above WHO permissible limits in some of the samples. The results from this study show that the habit of eating soil is exposing the pregnant mothers and their children to metal toxicity which is detrimental to their health. Hence, further actions should be taken to discourage the habit of eating soil at all levels.
Determination of essential and toxic elements in clay soil commonly consumed by pregnant women in Tanzania
(Elsevier, 2013) Mwalongo, D.; Mohammed, Najat K.
A habit of eating clay soil especially among pregnant women is a common practice in Tanzania. This practice known as geophagy might introduce toxic elements in the consumer's body to endanger the health of the mother and her child. Therefore it is very important to have information on the elemental composition of the eaten soil so as to assess the safety nature of the habit. In this study 100 samples of clay soil, which were reported to be originating from five regions in Tanzania and are consumed by pregnant womenwere analyzed to determine their levels of essential and toxic elements. The analysis was carried out using energy dispersive X-ray fluorescent technique (EDXRF) of Tanzania Atomic Energy Commission, Arusha. Essential elements Fe, Zn, Cu, Se and Mn and toxic elements As, Pb, Co, Ni, U and Th were detected in concentrations above WHO permissible limits in some of the samples. The results from this study show that the habit of eating soil is exposing the pregnant mothers and their children to metal toxicity which is detrimental to their health. Hence, further actions should be taken to discourage the habit of eating soil at all levels.
DETERMINATION OF RADIOACTIVITY IN MAIZE AND MUNG BEANS GROWN IN THE NEIGHBORHOOD OF MINJINGU PHOSPHATE MINE, TANZANIA
(College of Natural and Applied Sciences, 2014) Nkuba, Leonid L.; Mohammed, Najat K.
Two staple foods (maize and mung beans) which were cultivated in Minjingu village, where there is phosphate deposit in Tanzania, were collected directly from the farms. The activity concentrations of 226Ra, 228Th and 40K were determined in the maize and mung beans samples using γ ray spectrometry employing HPGe detector of relative efficiency of 51.0 %. The mean radioactivity level in the food samples were found to be 21.01 ± 0.8 Bq/kg (mung beans), 25.6 ± 0.7 Bq/kg (maize) for 226Ra, 62.6 ± 1.1 Bq/kg (mung beans), 72.9 ± 1.0 Bq/kg (maize) for 228Th and 542.9 ± 8.6 Bq/kg (mung beans), 434.6 ± 18.7 Bq/kg (maize) for 40K. The radioactivity content of the maize and mung beans from Minjingu village were higher than that of similar food samples collected from Bukombe district in Geita Region in Tanzania. The total annual effective dose for consumption of 226Ra and 228Th by adults was calculated to be 2.003 ± 0.044 mSv/year, which is higher than the annual dose limit of 1 mSv/year recommended by the ICRP for the general public. Hence a conclusion could be made that food crops cultivated at Minjingu village might expose the population to high radiation dose which might be detrimental to their health.
Distribution of Heavy Metals in Soils in the Vicinity of the Proposed Mkuju Uranium Mine in Tanzania
(Canadian Center of Science and Education, 2015) Banzi, Firmi B.; Msaki, Peter K.; Mohammed, Najat K.
Tanzania is at advance stages in the preparation to start uranium mining at Mkuju River Deposit. In order to implement best practice in environmental management in uranium mining as required by national and international regulations and standards, a set of site specific baseline data have to be established prior the mining operation. In order to establish heavy metal baseline data for this purpose, a total of 84 soil samples were collected from clustered area of about 1,300 km2 at two depths: 0-15 cm and 15-30 cm. Analysis of the data using EDXRF showed a total metal concentration ranges of 3570-19400 for Al, 15200-58600 Fe, 400-1400 Mn, 15.2-54.9 Cr, 13.5-51.0 Zn, 2.2-45.3 Pb, 2.1-37.3 Cd, 0.2-23.0 Hg, 1.8-25.1Cu, 2.1-22.7 Ni and 0.8-9.1 mgkg-1for Co. Since the spatial distributions of heavy metals in the vicinity of the planned uranium mine are comparable to established global concentration ranges in soils, it is an indication that the distribution is natural. By virtue of their strong association with uranium and immobility in soil, spatial distributions of lead and copper concentrations would be more sensitive indicators for monitoring uranium related soil contaminants when the uranium mine become operational.
Distribution of Heavy Metals in Soils in the Vicinity of the Proposed Mkuju Uranium Mine in Tanzania
(Canadian Center of Science and Education, 2015) Banzi, Firmi B.; Msaki, Peter K.; Mohammed, Najat K.
Tanzania is at advance stages in the preparation to start uranium mining at Mkuju River Deposit. In order to implement best practice in environmental management in uranium mining as required by national and international regulations and standards, a set of site specific baseline data have to be established prior the mining operation. In order to establish heavy metal baseline data for this purpose, a total of 84 soil samples were collected from clustered area of about 1,300 km2 at two depths: 0-15 cm and 15-30 cm. Analysis of the data using EDXRF showed a total metal concentration ranges of 3570-19400 for Al, 15200-58600 Fe, 400-1400 Mn, 15.2-54.9 Cr, 13.5-51.0 Zn, 2.2-45.3 Pb, 2.1-37.3 Cd, 0.2-23.0 Hg, 1.8-25.1Cu, 2.1-22.7 Ni and 0.8-9.1 mgkg-1for Co. Since the spatial distributions of heavy metals in the vicinity of the planned uranium mine are comparable to established global concentration ranges in soils, it is an indication that the distribution is natural. By virtue of their strong association with uranium and immobility in soil, spatial distributions of lead and copper concentrations would be more sensitive indicators for monitoring uranium related soil contaminants when the uranium mine become operational.
The elemental analysis of staple foods for children in Tanzania as a step to the improvement of their nutrition and health
(Elsevier, 2008) Mohammed, Najat K.; Spyrou, Nicholas M.
The objective of this study was to evaluate the contents of essential elements in the two staple foods (rice and maize flour) consumed by children in Tanzania as a possible selection measure for high nutrient foods in order to combat malnutrition. Samples were analysed using proton-induced X-ray emission (PIXE) at the University of Surrey Ion Beam Centre. The mean concentrations of elements determined in the two staple foods are presented and compared with the mean concentrations published in the literature.
Elemental Contents in Hair of Children from Two Regions in Dar Es Salaam
(Hindawi Publishing Corporation, 2012-01-12) Mohammed, Najat K.
The work presented in this paper is part of the study which aims at determining the levels of elements in hair of children in Tanzania as a bioindicator of their nutrition and health. In this paper, the levels of trace elements in hair from children living in Dar es Salaam have been analysed. The analysis was carried out by long and short irradiation INAA at the reactor centre of the Institute of Nuclear Physics, Rez Czech Republic. 22 samples were collected from children living at Kiwalani about 12 km from Dar es Salaam city and 16 samples from children living at Mlimani, the main campus of University of Dar es Salaam. A total of 34 elements were found in the hair of the children. There were no big differences between the concentration levels of the essential elements in hair samples collected from the children which might indicate the same food consumption habits.
Elemental contents in hair of children from Zanzibar in Tanzania as bio-indicator of their nutritional status
(Springer Netherlands, 2008-04) Mohammed, Najat K.; Mizera, Jiri; Spyrou, Nicholas M.
Nutritional status and toxic elements body burden were evaluated in hair of children living in Zanzibar. 18 samples were collected from Zanzibar town and 19 samples from Nungwi village, which is approximately 64 km from Zanzibar town. The analysis was carried out using instrumental neutron activation analysis (INAA). The concentration ranges obtained in this study overlap with the published elemental values of healthy children of the same age group. The concentration levels of K, Zn, Cu, As and Co in hair of children from Zanzibar town were higher than from Nungwi whereas levels of Mn, Br and Sr were lower.
Heavy Metal Concentrations in Soil and Green Vegetables (Vigna unguiculata) around Volcanic Mountain of Oldoinyo Lengai, Arusha, Tanzania
(SCIENCEDOMAIN international, 2015) Amour, Khamis O.; Mohammed, Najat K.
The aim of this work was to assess heavy metal concentrations of samples collected from areas around a volcanic mountain in Tanzania. Fifty five soil samples and 10 samples of bean leaves were analysed using Energy Dispersive X- ray Fluorescence spectrometry (EDXRF). The concentrations of heavy metals in the samples are presented, statistical analysed and compared with control. The concentration in bean leaves are also compared with the maximum tolerable limits set by FAO/WHO to assess their safety for consumption. The results from this study show that high concentration of elements in both soils and bean leaves samples from Oldoinyo Lengai areas might be associated with frequently eruptions of the volcanic mountain of Oldoinyo Lengai. Hence, farming in Oldoinyo Lengai areas is introducing heavy metals in the food chain.

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