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Effective verification for compliance with water quality standards in uranium mining in Tanzania
requires data sensitive to monitor heavy metal concentration in water around the Mkuju River
Uranium Project before mining commences. The area susceptible for pollution by the project was
estimated using AERMOD dispersion model and found to cover about 1300 km2. Thirty one surface
and groundwater samples were collected and analysed for heavy metals and physicochemical
properties using ICP-MS and standards techniques, respectively. The physicochemical properties for
water samples analysed ranges from 5.7 to 7.8 for pH, 2.8 to 80.2 mg/L for TDS and 15 to 534.5
mS/cm for EC. These values show that the water in the vicinity of the Mkuju River Uranium Project is
normal. The ranges of concentration of heavy metals (μgL-1) determined in water ranges were: Al(2 to
9049), Cr(0.2 to 19.96), Mn (0.1 to 1452),Fe(2 to 53890),Co(0.02 to 27.63), Ni(0.2 to 9.7), Cu(2 to
17), Zn(2 to 62.94), As(0.4 to 19.17), Cd(0.02 to 0.14), Pb (0.02 to 78.68), Th (0.002 to 1.73),U(0.002
to 29.76). These values are below the tolerance levels of concentrations set by different International
organisations. Therefore heavy metal toxicity in the study area is marginal. The parameters that could
serve as baseline data because of their enhanced sensitivity to pollution were (i) concentration of
chromium, cobalt, nickel, copper, zinc, arsenic, cadmium and lead in water (ii) pH, TDS and EC for
water, (iii) TDS ratio for surface to ground water values and (iv) correlation coefficients between the
heavy metals. However, since TDS values are season dependent, this indicator can serve as baseline
data when measured during the dry season as was the case in the study. |
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