Abstract:
Indiscriminate disposal of spent engine oil has been implicated as a major pollutant of soil and
water. The effects of which are felt along the aquatic and terrestrial food chains, where the
pollutants bioaccumulate in plants, fishes and other animals and when they are ingested by
man they pose serious health hazards. The objectives of this research are: to evaluate the
bioremediation potential of activated groundnut hulls (GAC) and rice husks (RAC) on spent
engine oil polluted soils, determine the effect of heavy metals on growth parameters of
cowpea (Vigna unguiculata L.) and to investigate the effects of agro wastes on the quality of
the seed by using insect pests of cowpea. Cowpea seeds were obtained from IITA Ibadan, Oyo
State and groundnut hulls and rice husks from open market in Makurdi and Akure
respectively. The experiment was carried out in the Federal University of Technology Akure
(FUTA), Ondo State. The two agro waste materials were processed into activated charcoals
which were used as treatments in three different concentrations. 20g, 30g and 40g.Each of the
treatments was introduced into plastic pots containing 7kg of top soil polluted with 30mls of
spent engine oil. Three plastic pots each containing 7kg of top soil were made as control and
another 3plastics containing 7 kg of top soil and 30mls spent engine oileach was made as
CO.All the set up were labeled and arranged randomly inside screen house for a week. Two
cowpea seeds each were planted in each pot and wet continuously every other day for
12weeks. Heavy metal concentrations in the soil, root, shoot and seed of the cowpeas sown in
all the 24 pots were evaluated. Some growth parameters of cowpea sown in the treated and
untreated polluted soil were measured weekly with the aid of thread and well calibrated
rulers. The data obtained were analyzed using one-way ANOVA and separated with Least
Significant Difference (LSD) (p < 0.05). There were statistically significant differences
between the stem girth of cowpeas planted on treated and untreated soil. Rice husks activated
charcoals (RAC) treated polluted soil in the 11th week produced a girth length of
2.13±0.07compared to untreated polluted soil with girth length of 1.50±0.00. The agro wastes
were effective in heavy metal remediation in treated polluted soils. However, RAC was more
effective in remediation than GAC. Therefore, activated charcoal from agro waste materials
should be encouraged in soil remediation because they are environmental friendly.
