Evaluation of nickel levels in wastewater, soil and vegetable samples grown along Kubanni stream channels in Zaria, Kaduna State, Nigeria

Abstract

The concentration of nickel was evaluated in wastewater, soil and vegetable (carrot, lettuce, onion, spinach, cabbage, tomato and okra) samples that were collected on seasonal basis from January, 2013 to September 2014 along Kubanni stream channels in Zaria. The results showed nickel concentrations in wastewater were in the range of 7.69 – 38.46 mg/L for the year 2013 and 7.68 – 27.04 mg/L in 2014; 1.92 – 21.37 mg/Kg for the year 2013 and 8.24 – 24.32 mg/Kg in 2014 for the soil while the vegetables had concentrations in the range of 6.97 – 18.79 mg/Kg for the year 2013 and 3.78 – 18.27 mg/Kg in 2014. Statistical analysis revealed no significant difference in nickel levels across the locations and seasons for wastewater, soil and vegetables analyzed. Pearson correlation showed substantial (r = 0.631) relationship between nickel levels in wastewater for the year 2013 and 2014, negative (r = -0.284) relationship was obtained for the soil between these two years whereas substantial (r = 0.634) relationship was obtained for vegetables cultivated in 2013 and that of 2014, respectively. Thus, nickel concentrations obtained in this study was higher than maximum contaminant levels set by Standard Organizations such as WHO and FAO for wastewater whereas the soil and vegetables were less to limits set by these bodies.