Browsing by Author "J., Kwetegyeka"

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Heavy metal contamination in vegetables cultivated on a major urban wetland inlet drainage system of Lake Victoria, Uganda
(International Journal of Environmental Studies, 2010-06) Jolocam, Mbabazi; J., Wasswa; J., Kwetegyeka; G.K., Bakyaita
The population of the Ugandan capital, Kampala, located close to Lake Victoria, appears to be exposed to risk of ingesting the heavy metals Cadmium (Cd) and Lead (Pb) through vegetables in their diet. Lake Victoria is responsible for frequent torrential polluted runoffs in the city. The Nakivubo channel, the city’s major wetland drainage system, empties directly into the lake. Vegetables are grown on the urban wetland soils. Heavy metal content in vegetables from the wetland cultivation sites was determined by wet acid digestion, with 87–92% recovery. The results showed that although the heavy metal levels of manganese (Mn), zinc (Zn), cadmium (Cd) and lead (Pb) were significantly higher than those in similar food crops from rural control sites, only Cd and Pb exceeded the World Health Organisation (WHO) maximum permissible levels. Cd and Pb pose serious human health risks. Early pollution control measures are advisable.
Ineffectiveness of Nakivubo wetland in filtering out heavy metals from untreated Kampala urban effluent prior to discharge into Lake Victoria, Uganda
(African Journal of Agricultural Research, 2010-12) Jolocam, Mbabazi; J., Kwetegyeka; M., Ntale; J., Wasswa
The population of the Ugandan capital city of Kampala has dramatically increased since the political turmoil of the 1970s and with it a considerable rise in industrialisation. Few manufacturing plants, however, have pretreatment installations in place for their polluted effluent prior to discharge into the surrounding ecosystems. Kampala’s main drainage system is the Nakivubo channel which empties directly into the neighbouring Lake Victoria, the second largest inland freshwater lake in the world. Increased urban effluent load coupled with reclamation for crop farming have considerably reduced the effectiveness of the wetland to filter out major pollutants, in particular heavy metals. Using atomic absorption spectrophotometry, this study showed that the efficiency in sieving out zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) has shrunk from 89.7 – 98.3% in December 2006 to 79.4 – 92.1% in December 2008, over a period of three consecutive years. This is indicative of the growing ineffectiveness of the wetland to absorb heavy metals. Levels of the same metals in the lake water some two kilometres away from the mouth of the wetland have correspondingly increased from 23 - 31% to 35 - 47% in the same period. This poses a serious threat to the quality of the fish and to the over two million urban population that directly depend on the lake water for domestic and industrial use. The remedy lies in the relevant authorities to enforce pretreatment at each factory site, increased factory management sensitisation on environmental concerns and more stringent measures against wetland encroachment.
Speciation of heavy metals in water from the Uganda side of Lake Victoria
(International Journal of Environmental Studies, 2010-02) Jolocam, Mbabazi; H., Twinomuhwezi; J., Wasswa; M., Ntale; G., Mulongo; J., Kwetegyeka; K.H., SchrǾder
Different forms of copper Cu, zinc Zn, lead Pb and cadmium Cd in water from the Uganda side ofLake Victoria (25°C, pH 6.75–7.18), the second largest inland freshwater lake in the world, havebeen studied using ion-exchange, dialysis and atomic absorption spectrophotometry. The resultsindicate that heavy metals Cu, Zn, Pb and Cd are present mainly in the cationic form (80–83%).Small quantities of anionic (13–22%), non-ionic, dialyzable (4–8%), and non-ionic, non-dialyzable(< 1.3–4.4%) forms were also detected for all metals except Cd. The corresponding concentrationslay in the ranges: cationic, 0.06–0.99; anionic, < 0.001–0.25; non-ionic, dialyzable, < 0.001–0.08;non-ionic, non-dialyzable, < 0.001–0.06 μg ml−1. The existence of the metals in non-ionic and non-dialyzable forms is attributable to metal associations with high relative molecular mass (RMM)organic matters.