Occurrence of Heavy Metals Concentration in Grown Food Crops (Manihot Esculenta and Colocasia Esculenta) Around Disused Ogbete Coal Mine in Enugu Metropolis, Nigeria

Abstract The major food crops frequently consumed by many communities in southeastern Nigeria are Manihot esculenta (cassava) and Colocasia esculenta (cocoyam). The crops are sometimes grown in disused mining sites which could contaminate the crops and pose health risks. This study was conducted to assess the occurrence and concentration of heavy metals in the soil and crop samples Manihot esculenta (cassava) and Colocasia esculenta (cocoyam) around the disused coal mine area in Ogbete Enugu, Nigeria. The five heavy metals studied were (Cd, Cr, Zn, Ni and Pb). The samples included twenty-four crops of which eighteen were collected from three sampling locations (farmlands in the disused coal mine area). The control samples were collected from a farm in the GRA Enugu area (farmland without coal mining activity). Using a double acid digestion procedure, Atomic Absorption Spectrophotometer (AAS) was used in laboratory analysis. The data generated were analyzed using ANOVA. The result indicated that the concentration of (Cd, Cr, Zn, Ni and Pb) in the soil samples at the farm within the disused coal mine area were higher than the concentration in the control area except for Ni concentration which is below in the Farm 3. The occurrence and concentration of heavy metals in food crops range from (0.00 – 0.103 for Cadmium), (0.00- 0.851for chromium), (0.00- 0.187 for zinc), (0.00- 0.851 for Nickel), and (0.00 – 0.015 for lead). Some heavy metals' concentrations recorded were below the WHO limits. The low values recorded could be attributed to the fact that the study area is not an active mining site. Also in crop samples, especially cocoa yam Ni and Zn were below the concentration in the control. However, the study emphasized that food grown in the disused mining site could pose human health risks. Hence, the study recommends the continuous monitoring of heavy metal concentration in the Ogbete disused coal mine in Enugu, Nigeria. The study also suggests that cocoyam can be recommended for phytoremediation of soil polluted by Nickel and Zinc.