Concentration of Heavy Metals (Cd, Co, Cr, & Fe) in Soil and Edible Vegetables in Obudu Urban Area of Cross River State, Nigeria

Abstract

The soil and edible vegetable samples were collected from Obudu Urban Area of Cross River State and were digested and analyzed for the Cd, Co, Cr, and Fe (heavy metals) concentration using Atomic Absorption Spectrometer (AAS) in the University of Calabar Laboratory. The eight vegetables considered for the study were Amaranthus spp., Corchorus olitorius, Murraya koenigii, Ocimum grattissimum, Solanum melongena, Talinum triangulare, Telferia occidentalis and Vernonia amygdalina. The results showed that the mean concentration of the metal in the soil in mgkg-1 ranged from (0.004-0.0048) and (0.005-0.046) in rainy and dry seasons respectively for Cd, (0.004-0.025) and (0.006-0.016) in rainy and dry season respectively for Cr, and (0.112-0.173) and (0.116-0.151) in rainy and dry season respectively for Fe. The concentration of Co was not detected in the soil or vegetables. The mean concentration accumulated by the vegetables and that present in the soil was in the order: Fe> Cd> Cr> Co. These results suggest that there is no significant difference between the amount of metals in the soil or that accumulated by the vegetables in rainy and dry seasons of the year. Also the amount of metals accumulated by most of the vegetables was directly proportional to the amount present in the soil where they are planted. The bioaccumulation ratios were all less than 1. These results indicate that the concentration of Cd, Co, Cr, & Fe in the soil and vegetables were still low and within the permissible limits of WHO/FAO. Thus, the consumption of the vegetables in the area may not cause any harm for now.