Assessment of Toxic Metals in Soil and Vegetable Samples from Irrigated Farmland in Kaduna Metropolis, Nigeria

Levels of Cd, Cr and Pb in (mg/kg) were determined in topsoil and vegetable samples from irrigated farmland using Atomic Absorption Spectrophotometer (AAS). The vegetables available as at the time of sampling and sample collection were spinach and 'yakuwa' leaves. The soil physico-chemical parameters, pH and percentage organic matter (%OM) content were also determined. Levels of Cd, Cr and Pb in all the soils were 0.1-6.5, 2.00-38.00 and 2.90-24.00 mg/kg dry weight, respectively. Concentration ranges of all the plants were 0.01-1.00, 0.80-8.00 and 0.20-11.00 mg/kg dry weight for Cd, Cr and Pb respectively. The soil pH showed slightly acidic to neutral which ranged from 5.05-7.50 while the soil percentage organic matter ranged from 0.29-2.23%. The mean concentrations of soil and plant samples studied were found to follow the decreasing orders; Cr greater than Pb greater than Cd and Pb greater than Cr greater than Cd respectively. There is correlation between soil physico-chemical parameters and metals such as Cr and Pb in soil samples while for vegetable plants there is correlation between metals such as Cd, Cr and Pb content. The levels of toxic metals are within tolerable levels except for Cd in soil and Pb in vegetable samples that has values which are higher than the FAO/WHO recommended values The slightly high level of Pb in the vegetables could be ascribed to deposits of the metal from vehicle emissions.