Browsing by Author "Muwanga, Andrew"

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    Exploratory geochemical assessment of stream water and sediment contamination in Gatumba tin and tantalum mining district, Rwanda.
    (2009) Flügge, Judith; Muwanga, Andrew; Trümper, Kerstin; Zachmann, Dieter; Pohl, Walter
    Stream waters are not contaminated with dangerous inorganic elements. According to WHO guidelines, these waters are acceptable for lifelong consumption without risk to health. Note, however, that microbial waterborne disease vectors were not investigated. Stream sediments generally have relatively low contents of most elements that may be derived from pegmatites. Of mine-related contaminants, only uranium and arsenic exceed their respective average crustal abundance. Both appear to be higher near former mine sites but this is probably not caused by mining. Causes are rather primary hydrothermal and secondary supergene dispersion, and recent mobilisation because of intensive agricultural use. Yet at present, the welfare of the local population is not threatened. The most serious hazard is human interference with groundwater by abstracting drinking water either from wells in valley fill or from deeper horizons of the regolith. Overall, our work suggests that past mining at Gatumba caused little dispersion of deleterious elements.
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    The geochemical signature of rare-metal pegmatites in the Central Africa Region: Soils, plants, water and stream sediments in the Gatumba tin–tantalum mining.
    (Journal of Geochemical Exploration, 2014) Nieder, Rolf; Weber, Tobias; Paulmann, Inga; Muwanga, Andrew; Owor, Michael; Naramabuye, Francois; Gakwerere, Francis; Biryabarema, Micheal; Biester, Harald; Pohl, Walter
    We studied trace elements in soils, plants, water and stream sediments in the Gisuma–Kibilira catchment of the Gatumba area of western Rwanda which has a long tradition of artisanal to small-scale tin–tantalum mining from rare-metal pegmatites. The geochemical fingerprint of soil, plant, water (springs and surface water in dry and rainy seasons) and stream sediment samples reveals elevated concentrations of Li, Rb, Cr, and Cs, but low As and U abundances at or below the global average. Trace element contents of soils and most plant materials are below internationally accepted guideline values. All water samples analyzed meet the World Health Organization (WHO) drinking water guidelines, and the stream sediments are below critical values of Dutch environmental standards. These data provide a baseline for environmental impact studies for rare-metal mining projects in the Central Africa Region
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    Recent glacial recession in the Rwenzori Mountains of East Africa due to rising air temperature.
    (Geophysical Research Letters, 2006) Taylor, Richard G.; Lucinda, Mileham; Tindimugaya, Callist; Majugu, Abushen; Muwanga, Andrew; Nakileza, Bob
    Based on field surveys and analyses of optical spaceborne images (LandSat5, LandSat7), we report recent decline in the areal extent of glaciers in the Rwenzori Mountains of East Africa from 2.01 ± 0.56 km2 in 1987 to 0.96 ± 0.34 km2 in 2003. The spatially uniform loss of glacial cover at lower elevations together with meteorological trends derived from both station and reanalysis data, indicate that increased air temperature is the main driver. Clear trends toward increased air temperatures over the last four decades of ∼0.5°C per decade exist without significant changes in annual precipitation. Extrapolation of trends in glacial recession since 1906 suggests that glaciers in the Rwenzori Mountains will disappear within the next two decades.
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    Variations in the contents of heavy metals in arable soils of a major urban wetland inlet drainage system of Lake Victoria, Uganda
    (Lakes & Reservoirs: Research & Management, 2010) Mbabazi, Jolocam; Bakyayita, Grace; Wasswa, John; Muwanga, Andrew; Twinomuhwezi, Hannington; Kwetegyeka, Justus
    Little is known about the effects of urbanization on the chemical quality of soils in suburban wetland inlet drainage systems to the Uganda side of Lake Victoria, on which food crops are extensively grown. It is feared that pollution in the soils might eventually enter food chains through such crops being consumed by urban populations unaware of their occurrence. Soil samples were collected from cultivated areas of a major wetland drainage system (Nakivubo Channel), at Kampala, Ubanda, near Lake Victoria and from a rural control wetland site (Senge). The soil from this site had similar properties as those from the urban test site (i.e., soil texture; porosity; humus content). Analysis of heavy metals with atomic absorption spectrophotometry (AAS) yielded the following soil concentration ranges: manganese (190–780), cadmium (<0.001–1.0), zinc (6.0–10.0) and lead (10–20 mg kg)1) dry weight for the control site, and 450–900, 1.0–2.0, 131– 185, 40–60 mg kg)1 dry weight, respectively, for the urban wetland, indicative of relatively heavy metal pollution in the suburban drainage system. Heavy metal levels in cocoyam (Colocasia Esculenta) and sugarcane (Saccharum Officinarum) grown on both wetland soils also were evaluated via AAS with a modified wet-acid-digestion technique. The results highlighted high cadium and lead levels (P £ 0.0003) in the crops from urban wetland cultivation. Cadmium and lead concentrations in cocoyam from urban wetland soils exceeded those from the control site by 0.17 and 3.54 mg kg)1, respectively. The corresponding results for sugarcane indicated a similar increase of 0.56 and 2.14 mg kg)1 of juice extract. Cadmium and lead levels in both urban wetland crops were higher than the maximum permissible limits of the Codex Alimentarius Commission, indicating that these concentrations pose potential health risks to urban consumers, and call for early counter-measures to combat urban pollution entering the lake.