Concentration of Heavy Metals in Soil from an Irrigated Farmland in Kaduna Metropolis, Nigeria.

Concentrations of Cd, Cr, Cu, Pb and Zn in (mg/kg) were determined in topsoil from irrigated farmland around Kawo area in Kaduna, a town in Northern Nigeria using Atomic Absorption Spectrophotometer (AAS). The soil physico-chemical parameters, pH and percentage organic matter (% OM) content were also determined. The soil pH showed alkaline which ranged from 6.50-7.90 while the soil percentage organic matter ranged from 0.80-1.86 %. Concentration of Cd, Cr, Cu, Pb and Zn in all the soils samples ranged from 0.1-4.5, 0.50-30.50, 3.2-13.5, 4.0-28.00 and 5.5-49.7 mg/kg dry weight, respectively. The mean concentrations of soil samples studied were found to follow the decreasing orders; Zn > Pb > Cr > Cu > Cd. There is correlation between soil physicochemical parameters and metals such as Cu and Pb in the soil samples. The concentrations of heavy metals are within tolerable levels except for Cd. The slightly high level of Cd could be ascribed to lubricating oils as well as the burning of old tyres that are frequently dumped close to the site.