Landfill leachates pose a significant threat to both surface water and groundwater especially the wells adjacent to landfills. The study investigated the bioavailability of zinc (Zn), copper (Cu), lead (Pb), cadmium (Cd) and mercury (Hg) from leachates of ten huge dumpsites across the metropolitan city of Zaria. The trends in the mean concentrations of the metals (mg/L) among the fractions were; Zn: total > mobile > particulate > dissolved; Pb: total > mobile > particulate > dissolved; Cd: mobile > dissolved > total > particulate; Hg: particulate > mobile > total > dissolved, respectively. All the concentrations of the metal ions were above the world Health Organization (WHO) (2006) and United States Environmental Protection Agency (USEPA) (2000) tolerable limits across the sites, with the exception of lead at the control site which was not detected. The order of the metals bioavailability was; Cd > Hg > Zn > Pb > Cu, with more than 49% found in the bioavailable phase. Thus, the underground waters within the vicinity of the dumpsites were greatly at the risk of being polluted by these toxic metals and subsequently affecting the inhabitants who use the water for drinking and other domestic activities untreated, through the food chain transfer. The health implications associated with the toxic metals include an irreversible damage to nervous system, gastric and intestinal disorder, heart disease, liver, brain damage, mental retardation and teratogenic effects.
Key words: Fractionation, heavy metals, leachates, dumpsites, Zaria.
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