EFFECT OF SPENT OIL CONTAMINATED SOIL ON THE GROWTH OF AMARANTHUSHYBRIDUS AND POPULATION OF EARTHWORM EUDRILUSEUGENIAE

The effect of spent lubricating oil (SLO) on the growth of Amaranthushybridus, a staple leafy vegetable; and on the population build-up of earthworm were investigated. The treatment consisted of 0, 10, 20, 30, 40, 50 and 60ml of spent lubricating oil per kilogram of soil in 3 replicates. Two seedlings, each of A. hybridus were planted in perforated pots containing soil rich in earthworm in each replicate. Baseline analysis of SLO and soil was carried out. Stem, soil, and earthworm were analyzed for copper, lead, cadmium, zinc, and nickel at 6 weeks post treatment. There was significant growth retardation with corresponding increase in level of SLO. There was no significant difference in the plant parameters among the treatments. There was no population build-up of earthworm in all the treatments except in the soil with lowest contamination of 10ml/kg and control. The A. hybridus stem had significantly higher levels of Zn, Cd and Cu than controls; but cadmium was not detected. For soil Zn, Pd and Cd were higher in all treatments; Ni was significantly higher only at the 60ml/kg concentrations with a value of 0.14±0.014mg/kg while Cu was significant in all treatments except in the 10ml/kg and control with values of 0.097±0.002 and 0.087±0.002 respectively. For earthworm, Zn, Ni, Cu, and Cd were detected with the highest concentrations in the 10ml/kg. The level of heavy metals in treated soil exceeded WHO MPL. The bioaccumulation of metals intreatments may lead to biomagnification along the food chain leading to hazardous effects on humans.