Quality assessment of the physicochemical properties of soils from automobile workshops and transformer installations site in Lafia, Nasarawa State

Abstract

Analysis of soils for physical and chemical properties from selected auto-mechanic workshops and transformer installations in Lafia town, Nasarawa State was carried out according to standard methods. The levels of heavy metals concentration in the soil were assessed using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES Thermo Fisher ICAP 6300). The results obtained for the physicochemical properties and concentrations of heavy metals in the auto-mechanic workshops and the transformer installations varied according to the sampling locations and the type of metals. It was observed that in the auto-mechanic workshops, the levels of these metals were: Co (0.50-0.72 mg/kg), Fe (1.36-1.96 mg/kg), Pb (0.53-0.69 mg/kg), Cu (1.49-1.79 mg/kg), Cd (0.94-1.12 mg/kg), Ni (0.05-0.10 mg/kg), and Zn (10.14-11.14 mg/kg) while that of the transformer site ranged: Co (0.88-0.96 mg/kg), Fe (1.35-1.77 mg/kg), Pb (0.06-0.08 mg/kg), Cu (0.75-0.92 mg/kg), Cd (0.05-0.11 mg/kg), Ni (0.12-0.15 mg/kg), and Zn (6.00-7.14 mg/kg). The values obtained for the physiochemical parameters of the soil samples varied with the nature of activities taken place where samples were collected. The pH of the soil from the auto-mechanic workshop ranged from: (5.87-6.20), conductivity (77.59-126 s/m), organic carbon (0.63-0.93), organic matter (1.08-1.60), sand (66.14-89.05), clay (4.91-14.95), silt (6.04-22.03), sulphate (2.16-3.14), and phosphate (2.16-4.08). Values obtained for the soil from the transformer installations site showed that the pH ranged (5.55-6.54), electric conductivity (86.22-121.92 s/m), organic carbon (0.46-0.97), organic matter (1.21-1.48), sand (74.14-89.47), silt (6.28-13-33), clay (4.25-12.53), sulphate (3.21-4.16), and phosphate (3.22-4.12), respectively. Although most of the physicochemical parameters of the samples analyzed are in conformity with the standard soil guideline range, the results obtained for heavy metals revealed that soils from some of the sampling locations are impacted negatively as observed in the significant concentrations of some heavy metals which are above the threshold limit for normal agricultural soil.