Cadmium, Cobalt, Lead and Zinc Levels in Soil and Edible Vegetables in Yala Urban Area of Cross River State, Nigeria

Abstract

The average level of cadmium (Cd), cobalt (Co), lead (Pb) and zinc (Zn) in the soil and edible vegetables samples collected randomly in Yala Urban Area of Cross River State was determined using flame Atomic Absorption Spectrometer. The samples were digested and analyzed for the metals level or concentration in Chemistry Laboratory, University of Calabar. The eight vegetables selected for the study were Amaranthus spp., Corchorusolitorius, Murraya koenigii, Ocimum grattissimum, Solanum melongena, Talinum triangulare, Telferia occidentalis and Vernonia amygdalina. The results indicated that the average level of the metals in the soil in mgkg-1 ranged from (0.005-0.021) and (0.004-0.019) in rainy and dry seasons respectively for Cadmium, (0.162- 0.475) and (0.163- 0.472) in rainy and dry season respectively for Cobalt, and (0.434-1.030) and (0.432-1.027) in rainy and dry season respectively for Zinc. Also, the average level of the metals accumulated by the vegetables in mgkg-1 ranged from (0.002-0.009) and (0.001- 0.007) in rainy and dry season respectively for Cadmium, (0.050-0.198) and (0.048-0.195) in rainy and dry season respectively for Cobalt, and (0.158-0.383) and (0.156-0.380) in rainy and dry season respectively for Zinc. The level of Lead in the soil or vegetables was not detected. The average level of metals accumulated by the vegetables and that present in the soil was in the order: Zinc > Cobalt > Cadmium > Lead. These results revealed that there is no significant difference between the level of metals in the soil or that accumulated by the vegetables in rainy and dry seasons of the year. Also the level of metals accumulated by most of the vegetables was directly proportional to the amount present in the soil where they are planted. The Target Hazard Quotients of these metals was less than 1. These results imply that the concentration of Cadmium, Cobalt, Zinc and Lead in the soil and vegetables were still low and within the permissible limits of World Health Organization. Thus, the consumption of the vegetables in the area may not pose any health risk for now. Keywords: Heavy metals, Concentration, Soil, Edible vegetables.