Phytoassessment of a waste engine oil-polluted soil exposed to two different intervals of monitored natural attenuation using African yam bean (Sphenostylis stenocarpa).

The present study comparatively investigated the phytotoxic effects of waste engine oil (WEO)-polluted soil exposed to monitored natural attenuation up to 5 and 14 months respectively. Soil was previously polluted with WEO at 0, 1, 2.5, 5 and 10% w/w oil in soil. Although, there was significant reduction in heavy metal concentration of soil as well as total hydrocarbon contents, performance of Sphenostylis stenocarpa was greatly retarded when sown at 5 months after pollution (MAP), with death of all seedlings except in the control. However, growth and yield performances were significantly (p > 0.05) enhanced at 14 MAP. Computation of hazard quotient showed that ecological risk factor initially posed by the presence of heavy metals in the soil at 5 MAP was significantly (p > 0.05) reduced to safe levels at 14 MAP.

Effects of spent lubricating oil on the growth of Capsicum annum L. and Lycopersicon esculentum Miller.

Susceptibility of the hot pepper (Capsicum annum L.) and the tomato (Lycopersicon esculentum Miller) to spent lubricating oil was investigated in soils supplemented with concentrations of oil ranging from 1-5% w/w. Treatment of soil with 4 and 5% spent oil consistently inhibited germination of both crops. Eighty-four days after sowing, the mean height and leaf area of C. annum in soil treated with 3% spent oil gave the lowest values. These were 3.14 +/- 0.6 cm and 0.24 +/- 0.01 cm(2) compared with respective values of 19.2 +/- 0.2 cm and 2.9 +/- 0.3 cm(2) for control plants. Premature death was observed in the case of L. esculentum plants treated with all tested strengths of spent lubricating oil.