[en] Moessbauer spectroscopy has been used to establish the valence state and magnetic structure of synthetic idaite (Cu_5.5FeS_6.5). Idaite was synthesized from pure elements and the phase purity was characterized by both X-ray diffraction and optical microscope Moessbauer measurements were made at 295K, 77K and 10K. The iron in idaite was found to be in trivalent state in tetrahedral coordination. Idaite orders magnetically but not completely at low temperatures the transition being observed at 50±3K. The spectrum at 10K was not well resolved, had very broad line width indicating hyperfine magnetic distribution characteristic of a non stoichiometric compound. (author)

[en] This study reports on the optimization and calibration of the Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer installed in the Department of Physics, University of Dar Es Salaam. The spectrometer was subsequently utilized to determine concentrations of heavy metals in water hyacinth (Eichhornia crassipes (Mart) Solms.) found growing along the shore of Lake Victoria. The optimal conditions and detection limits were determined experimentally by variation of the excitation parameters. The study found that the use of a collimator with two apertures of diameter 4 mm each placed 8 mm apart and made of materials that do not interfere with elements to be determined from the samples, gave lowest detection limits. The optimal pairing of voltage and current was found to be 40 kV and 30 mA while measuring time was 2000 seconds. Roots of the water hyacinth were used in experiments to check the validity and sensitivity of the equipment. The water plants were collected from areas influenced by industrial and domestic sewage around Mwanza town, namely Mwanza South, Mwanza Central and Mwanza North. Mwanza North had quite a few industries and human settlements. The samples were each oven-dried, ground into a fine powder and pressed into a pellet. Water hyacinth from the industrial area and those from sewage discharge points were found to have higher concentrations of heavy metals (K, Ca, Sc, Ti, Mn, Fe, Co, Ni, Zn and Pb) than those from non polluted area. A more detailed study, involving more samples, is needed in order to be able to statistically quantify the differences.(author)

[en] The aim of the study was to determine element concentrations in lungfish and catfish from the river Mara with INAA and EDXF to assess the health impact of the North Mara gold mine (NMGM) in Tanzania. Twenty samples of each species were collected from two sites downstream and upstream along the river Mara in the vicinity of NMGM. The sampling sites were 70 km apart. Significantly higher concentrations (p ≤ 0.05) of Cr, Ni, Cu, and Se in one of the species taken downstream than in those taken upstream might indicate contamination of the river Mara caused by the mining activities. (author)

[en] This study has estimated the concentrations of radon gas and respirable ore dust in the Merelani underground tanzanite mines. Two different portable monitors were used to measure the radon gas and respirable ore dust concentrations respectively. The mean radon gas concentration (disintegrations per second per cubic meter) ranges from 40.1 Bq/m"3 to 4.2x10"3 Bq/m"3 with the geometric mean of 118.4 Bq/m"3 which is below the ICRP workplace guidance level of 500 – 1500 Bq/m"3. The estimated mean annual effective dose (D) was 1.6 mSv which is significantly lower than the external exposure annual effective dose of 20 mSv and the annual organ dose limit of 2.4 mSv. The overall concentrations of respirable ore dust arithmetic mean was 18.2 g/m"3 and the geometric mean of 2.1 g/m"3 which is very high compared to the guidance level of 2 g/m"3. The respirable dust was mainly produced during drilling and blasting of rocks, under normal conditions the geometric mean of respirable gas concentrations was 0.8 g/m"3. It is recommended that immediate intervention such as providing proper ventilation during the two processes to dilute radon levels in underground mines and the monitoring should be done regularly. (author)

[en] This study reports on determination of concentrations of trace and toxic heavy metals in soil and vegetables grown near of Manyoni uranium deposit. Soil and vegetable samples were collected from five sites namely Mitoo Mbuga, farming area, Miyomboni, Tambukareli and near water pump. The concentrations of heavy metals in soil and edible vegetables samples were analyzed using Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF).All vegetable samples were found to have higher concentrations (in μg/g) of trace elements such as Ni (67.3) in pea leaves, Cu (14.9) in pumpkin leaves, Fe (478.6), (200.5) and (337.1) in pea, pumpkin and spinach leaves respectively, than the maximum tolerable limits recommended by WHO/FAO. Mean concentration of Pb (1.6 μg/g) in pumpkin leaves collected from Miyomboni (area D) were observed to be higher than the safe limit of (0.3μg/g) set by Codex 2006. Toxic elements concentrations (in μg/g) such as Cd (10.4), Pb (23.2),Hg (4.1), Th (31.5) and U (23.9) were observed to be high in soil collected from Mitoo Mbuga and farming area. Therefore, vegetables in the vicinity of Manyoni uranium deposit can expose people to toxic elements which are detrimental to their health.A more detailed study involving other foodstuffs is needed to establish conclusive results.

[en] Air pollution studies in Africa are limited and the influence of ambient air quality on buildings and constructions have not been investigated in the larger part of Sub-Saharan Africa. The increasing burden of emission from industry, traffic and coal power plants on ambient air pollution in Sub-Saharan Africa necessitated reviewing previous and current studies. In South Africa a 20-year exposure program, focusing on the effect of ambient exposure on various metals and alloys, showed that the amount of rainfall, relative humidity, atmospheric pollution, wind speed, solar radiation and structural design are some of the factors controlling atmospheric corrosion. Tanzania, being among the Sub-Saharan African countries and partly bordered by Indian ocean, the main source of marine atmosphere, experiences corrosive degradation on metal roofing and cementitious materials. This paper describes the exposure site set-up and will report on some preliminary results of air quality and its relation with the meteorological conditions, as well as surface changes observed, for the year one of exposure. These will thereafter be compared to the completed European and Asian studies, as reported by CLRTAP and RAPIDC respectively. (author)