Browsing by Author "Ikingura, J.R."

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    Monitoring of Heavy Metal Loading into the Wetlands South of Lake Victoria Basin, Nothern Tanzania
    (2009) Mutakyahwa, M.K.D; Ikingura, J.R.; Mtui, Godliving Y. S.
    The paper discusses sources, concentrations and physicochemical parameters of heavy metals of environmental concern in the wetlands of Lake Victoria basin in Tanzania. The metals investigated include copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), nickel (Ni), arsenic (As), manganese (Mn), cobalt (Co) and mercury (Hg). These metals are released into the wetlands via weathering and erosion of rock formations, mining operations and industrial activities, discharge of municipal and domestic waste, and use of agrochemicals. The levels of these heavy metals in soil, sediment, water, and biota differ. Wetlands impacted by gold mining activities in the South Lake Victoria basin show elevated heavy metal contents in soil and sediment, particularly Cu (13-415 mg/kg), Pb (24-94 mg/kg), Zn (9-80 mg/kg), Cr (19-77 mg/kg), Ni (12-37 mg/kg) and Hg (0.19-1.76 mg/kg), contrary to non-impacted wetlands, which contain relatively low concentration of these metals (Cu 1-18 mg/kg, Pb 0-27 mg/kg, Zn 5-22 mg/kg; Cr 5-25 mg/kg, Ni 2-8 mg/kg, Hg <0.075 mg/kg). Elevated metal concentrations in soil and sediment are correlated with high metal contents in some plants within the affected wetlands. Oxidation and leaching of sulfide-bearing gold mine tailings resulted in acid mine drainage (AMD) with pH 3.25 - 4.10) and enhancement of heavy metal load and dissolved solids in streams draining into Nungwe Bay wetland on the southwestern shore of the Lake Victoria. Water samples from Bulyankhulu wetland drainage system were found to contain abnormally high Cu concentrations in the order of 270 mg/l. Samples from Mwakitolyo-Isanga and Nungwe Bay had higher values of Cr concentrations than those from Bulyankhulu and Luchili wetlands. Manganese was recorded to be 2.04 mg/L in a sample from Nungwe Bay, the reason being its mobilization from deeply weathered terrain associated with iron oxides
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    Vegetation Structure and Heavy Metal Uptake by Plants in the Mining-Impacted and Non Mining-Impacted Sites of Southern Lake Victoria Wetlands
    (2006) Mtui, Godliving Y. S.; Mligo, C.; Mutakyahwa, M.K.D.; Ikingura, J.R.
    This study assessed the plant species composition and the heavy metal uptake by plants in the mining-impacted and non mining-impacted areas of the southern Lake Victoria basin. The vegetation of the wetlands was stratified into riverine forest, riverine thickets, swampy grassland, open woodland and floodplain grassland. Plant diversity at Nyamtukuza ranged between 2.34 to 2.70; at Geita was 2.29 to 2.57 and Mwakitolyo was between 1.08 to 1.70, which was significantly lower than the other two sites; whereas variation in plant species richness was not significant. TWINSPAN classification resulted into four clusters of the vegetation communities. Cluster A, a shrubby community with Combretum molle, Bersama abyssinica, Acalypha ornata and Acacia brevispica indicated previous cutting of woody species from the area. Cluster B was a severely disturbed community with Bidens pilosa and Anthocleista grandiflora as early successors. Cluster C was a community with moderate disturbance levels and cluster D was of wetland vegetation community types with indicator species such as Pistia stratiotes and Corchorus aestuans that are characteristic permanent wetland species. CCA ordination showed a significant positive correlation of the soil mineral elements to those in plants at axis 1. The influence of soil minerals on plant species distribution pattern was not significant at axis 1.