Assessment of Heavy Metals in Ground Water from Nasarawa State, Middle Belt, Nigeria

Aim: To assess contamination of borehole water by heavy metals (Fe, Zn, Pb, Cr, Cu, Ni, Mn).

Study Design: Water samples collected from fifty two boreholes in twelve Local Government Areas (L.G.A) of Nasarawa State were analyzed for the heavy metal concentrations.

Place and Duration of Study: Samples were collected from Akwanga, Awe, Doma, Garaku, Karu, Keana, Keffi, Lafia, Nasarawa, Nasarawa Eggon, Toto, and Wamba, during the dry season.

Methodology: The water samples were prepared according to standard methods. Heavy metal levels in the samples were quantitatively determined using atomic absorption spectrometry (AAS).

Results: The highest concentrations of Zn (1.81±1.19 mg/l) and Fe (0.89±1.73 mg/l) were recorded at Keana, while their lowest levels were observed at Lafia. Pb ranged from 0.01±0.00 to 0.04±0.05 mg/l in the areas. The highest Cu (0.32±0.51 mg/l) and Ni (0.07±0.06 mg/l) contents were obtained at Doma. Nasarawa recorded the highest concentration of Mn (0.08±0.04 mg/l) and the lowest at Lafia (0.01 ± 0.00 mg/l). Water Cr contents was highest at Keana (0.24±0.32 mg/l) and lowest at Lafia and Akwanga. Ni levels were low. Analysis of Variance (ANOVA) indicated that heavy metal concentrations were not significantly different (P < .05), except for Zn. Fe levels (0.70 mg/l) at Kagbu Error (N/Eggon), Offu and Ugya (0.75 mg/l) at Toto, where higher than the SON and WHO acceptable limits for drinking water, except at Idadu, where the value (0.35 mg/l) was within the WHO acceptable limit. Concentrations of Pb in borehole water from Tide, Nidan, and Towship (Akwanga), Arusu (0.014 mg/l) in Garaku and Keana were above the WHO threshold value for drinking water. Cr levels at Idadu (0.70 mg/l) in Doma, Angbragba (0.7 mg/l) and Owene (0.21 mg/l) at Keana, and Main market (0.07 mg/l), were also above the SON and WHO acceptable limits. Concentrations of Cu at Galle South (1.03 mg/l) in N/Eggon and Yashi Madaki (1.05 mg/l) in Wamba were higher than the SON standard but within the acceptable WHO (2.0 mg/l) standard.

Conclusion: Boreholes water was not contaminated by Mn, Zn, and Ni. Pb, Fe, Cu, and Cr levels in water were above SON and WHO. Metal levels above the standards might be attributed to surface contamination originating from anthropogenic and geological sources. Continuous monitoring of the heavy metal levels in water from the boreholes is recommended.