Mobility Profiles of Some Heavy Metals in Soil Samples from Selected Areas of Ado Local Government Area, Benue State, Nigeria

Abstract

During the rainy season, soil samples (at depths of 5 cm, 10 cm, and 15 cm) were collected from 15 different spots from five selected locations (NFS, NRL, NS1, NS2, and NR as control) in Ukwonyo Utonkon in Ado Local Government Area of Benue State, and analyzed for total metal concentration and mobility using standard methods. The percent loss on ignition (% LOI) at the different soil depths, which measures the organic matter content of the soil, showed that sample NRL was highest in organic matter loss (17.30%) at 5 cm soil depth. The total heavy metals concentration of the soil samples showed no specific trend in the level of heavy metals at the different soil depths. However, the metals distribution ranged from 4 mg/kg of Ni (for sample NRL3) to 1000 mg/kg of Ag (for sample NFS3) at 15 cm that showed a high potential for Ag content. Hg, Pb, and Sn were not detected in all the soil samples. The mobility of the metals in the soils varied considerably from one area to another with random increase and decrease according to soil depths. Mobility was highest for Ag (69.4 mg/g) in soil sample NFS, but Zn was not detected in the control sample NR at mean depth. The concentrations of the metals in soils from this study area were lower than their recommended levels for soil quality and indicated no threat to human health by the use of the soils for agricultural purposes.