Assessment of the impact of human settlement on the heavy metal concentrations of lower cross river, Nigeria

The impact of human settlement on heavy metal concentrations was assessed in the surface waters of Lower Cross River, Nigeria. Samples were collected from January to August, 2011 from three stations: Station 2 (Itu in Akwa Ibom State with intense human activities), station 1 (its upstream at Cross River State without human settlement) and station 3 (the downstream). The range of these heavy metals in the river were 1.0027 – 4.1225 mg/l for Mg, 0.0001 – 2.3703 mg/l for Fe, 0.0001 – 0.4118 mg/l for Zn, 0.0855 – 3.5701 mg/l for Pb, 0.0011 – 1.2582 mg/l for Cd, 0.0249 – 2.4856 mg/l for Cr, and 0.0001 – 0.9117 mg/l for Ni. The rank profile of metals according to their mean values was Mg > Pb > Fe > Cr > Cd > Ni > Zn in the study stations. The statistical analysis using the One-Way Analysis of Variance (ANOVA) showed that there was significant difference (P<0.01) in the concentrations of heavy metals at the study, except for Zn and Ni. Tukey’s pairwise comparism indicated that Station 1 was basically responsible for the observed significant differences in the study stations. Except for Zinc, all the other heavy metals exceeded the WHO and SON maximum permitted levels for drinking water indicating pollution. This could be attributed to anthropogenic inputs from upstream and run-off during wet season. The wet season concentrations were higher than those for dry season.

کلیدواژه ها:

Impact ، Human settlement ، Heavy metal concentrations ، Lower cross river ، Nigeria