Browsing by Author "G. K., Bakyayita"

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    Assessment of levels, speciation, and toxicity of trace metal contaminants in selected shallow groundwater sources, surface runoff, wastewater, and surface water from designated streams in lake Victoria Basin, Uganda
    (Journal of Environmental and Public Health, 2019-05) G. K., Bakyayita; A. C., Norrström; R. N., Kulabako
    The levels, speciation of elements, and toxicity of selected trace metals as well as other parameters in selected surface water, shallow groundwater sources, landfill leachate, and associated surface runoff in the Lake Victoria basin, Uganda, were studied. The WHO guidelines, Ugandan standards, Canadian guidelines and Swedish EPA were used for assessment. The shallow groundwater was acidic with pH values below 6.5. The pH, dissolved organic carbon, flouride, and sulphate levels for all springs were below the guideline values although 52.8% was contaminated with nitrates while 39% was contaminated with chloride ions. Some surface water samples had levels of major elements, such as iron, chromium, aluminium, and manganese, above the guideline values. Speciation studies showed that 74% of the metal ions was bound to dissolved organic matter in surface water, whereas in landfill leachates, the dominant ionic species was metal hydroxides or fulvic acid bound. Risk analysis based on the Swedish EPA showed varied risks of negative effects in 30%–76% of the sample sites ranging from high to increased risk in surface water, whereas the results from modelling sorption data using the Bio-met tool showed potential risk to toxicity effects of Cu2+, Ni2+, Zn2+, and Pb2+ in 15.3%–30.8% surface water samples and 8.3%–62.5% groundwater samples.
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    Competitive and noncompetitive batch sorption studies of aqueous cd(ii) and pb (ii) uptake onto coffea canephora husks, cyperus papyrus stems, and musa spp. peels
    (Journal of Chemistry, 2015-09) G. K., Bakyayita; A. C., Norrström; R. N., Kulabako
    Coffea canephora, Cyperus papyrus, and Musa spp. were studied for competitive and noncompetitive removal of aqueous Cd2+ and Pb2+. The optimal conditions were pH 4.5 and agitation time 3.0 hours. Biomass constituent ions showed no interference effects whereas cation exchange capacity values corresponded to the sorption efficiencies. XRD spectroscopy revealed surface oxygen and nitrogen groups that provide binding sites for metal ions. The maximum sorption efficiency ranges for metal ions in noncompetitive media were 95.2–98.7% for C. canephora, 42.0–91.3% for C. papyrus, and 79.9–92.2% for Musa spp. and in competitive sorption 90.8–98.0% for C. canephora, 19.5–90.4% for C. papyrus, and 56.4–89.3% for Musa spp. The Pb2+ ions uptake was superior to that of Cd2+ ions in competitive and noncompetitive media. In competitive sorption synergistic effects were higher for Cd2+ than Pb2+ ions. The pseudo-second-order kinetic model fitted experimental data with 0.917 ≤ 𝑅2 ≥ 1.000 for Pb2+ ions and 0.711 ≤ 𝑅2 ≥ 0.999 for Cd2+ ions. The Langmuir model fitted noncompetitive sorption data with 0.769 ≤ 𝑅2 ≥ 0.999; moreover the Freundlich model fitted competitive sorption data with 0.867 ≤ 𝑅2 ≥ 0.989. Noncompetitive sorption was monolayer chemisorption whereas competitive sorption exhibited heterogeneous sorption mechanisms.