Assessment of heavy metals and Total Petroleum Hydrocarbons accumulation in Tomato (Solanum lycopersicon L.) grown on Spent Oil polluted soil.

Abstract

Oil-polluted soils make agricultural lands less productive and unsuitable for food production particularly increasing toxic levels of certain crops. The environmental concern is exacerbated by indiscriminate discharge of Spent Lubricating Oil (SLO) on agricultural land in Nigeria. This study evaluated the accumulation of heavy metals (Copper (Cu), Nickel (Ni) and Lead (Pb)) and Total Petroleum Hydrocarbons (TPHs) in tomato plants grown on spent oil- polluted soil. The treatments were 0, 75, 150 and 300 mls levels of pollution, replicated five times and laid out in a completely randomized design. Data were collected on plant growth and yield parameters and analysed using ANOVA at p<0.05. There were significant decrease in plant height, number of leaves and stem diameter with increase in levels of spent oil pollution. The control (0ml) recorded significant increase in plant height (40.10cm), number of leaves (15.00) and stem diameter (0.50cm). The average fruit weight in the control was 0.80g while there were no fruits in other treatments. The highest dry weight (0.87g) was from the control while the lowest (0.69 g) was recorded from 75 mls treated plot. There was a general reduction of heavy metal concentrations in the soil with Cu having (7.38mg/kg) and Pb (0.70mg/kg) at 300 mls treatment while Ni was not detected. The control recorded the lowest TPH of 200mg/kg while the 300mls treatment had the highest 2800 mg/kg. In the plant shoot and root; Cu was higher (16.30mg/kg) in the root than in shoot (6.84mg/kg) while Pb (0.41mg/kg) in the shoot was higher than the root (0.21mg/kg) at 300 mls. This study shows that tomato plants could not survive the lowest (75mls) level of pollution; which signifies that small amount of spent oil in soil is unsafe for food crop production and consumers due to high levels of heavy metals and Total Petroleum Hydrocarbons.