ABSTRACT

It is a common practice in Nigeria especially by motor mechanics to dispose spent oil into gutters, water drains, open vacant plots and fanns. The effect of spent oil on the nitrogen and heavy metal content on vigna plants was investigated as well as creating opportunity for plant breeders in searching for ways of improving cowpea production in oil producing areas. The effect of spent oil contamination was studied on three different species of vigna (Vigna dekindtiana, Vigna marina and Vigna vexillata) at four different concentrations. The four different concentrations of spent oil graded from 50%, 100%, 150% and 200% of which each treatment has three replicates. The results show that a negative relationship existed between the oil levels in the soil and the growth (number of leaves, yellowness of leaves, folding of leaves and leaf drop) observed. The reductions and morphological effects in the growth and characteristics observed in the plants with spent oil increased as the concentration level of the contaminant increases compared to the control. Therefore, spent oil in soil has highly significant effects of some soil properties which include nitrogen and heavy metal properties .The morphological changes and observed heavy metal alterations in the plants was discussed as a possible tool in phyto monitoring and phytoremediation. The soil and plant used for this project work were properly buried to prevent the reintroduction of the heavy metal parts of plants and soil into the food chain, since not all accumulated heavy metals are phyto extracted or completely degraded by plants.