Assessment of Show Star Grass (Melampodium Paludosum) for Phytoremediation of Motor Oil Contaminated Soil

Abstract

Environmental pollution by petroleum and petroleum based products is a serious concern in pollution studies because of their structural complexity, slow biodegradation, bio- magnification potential and the serious health hazards associated with their release into the environment. Petroleum and allied products may enter the soil environment from ruptured pipelines, from land disposal of refinery products, petroleum wastes, leaking storage tanks, accidental spill and sometimes outright sabotage. Physical, chemical and thermal methods are already being used to remediate oil contaminated sites but their enormous costs, adverse effects on the environment and low efficiencies associated with these techniques limit their use and availability hence the use of biological methods like phytoremediation are being evaluated as alternative for the removal of pollutants because of their cost and safety of implementation.In this study, we investigate the potential of show stat grass (Melampodium Palusodum) a leguminous plant species which grows in tropical Nigeria for phytoremediation of laterite soil contaminated with motor oil. Our results indicate the following: that Show star grass (Melampodium palusodum) can grow, sustain growth and can survive in a motor oil contaminated laterite soil environment and can tolerate motor contaminated laterite soil at a concentration of 75.46 mg/g. Also, at a concentration of 75.46 mg/g in motor oil contaminated laterite soil environment, show star grass will stabilize and grow steadily after 8 weeks and enhances the degradation of motor oil in the contaminated laterite soil. Our results further indicate that Show star grass (Melampodium palusodum) reduced the initial TPH content in the contaminated soil from 75.46mg/g to 49.822 mg/g in two weeks after plant stabilization to 30.07 mg/g after 16 weeks of plant stabilization.

From the plot of TPH remaining in the soil against time, a polynomial model fit of the form:

y = - 0.0675x² +0.0879x + 47.754 is developed from which  it is predicted that it will take about 28 weeks after the stabilization of the plants to reduce the total petroleum hydrocarbon (TPH) content in the contaminated soil to zero. The study revealed that the amount of hydrocarbon removed per plant from the contaminated soil ranges from 4.273mg/g after 2 weeks to 7.564 mg/g after 16 weeks of testing with corresponding removal efficiency ranging from 33.97% to 60.14% and hence it is concluded that Show star grass (Melampodium palusodum) has potential phytoremediation application in motor oil contaminated laterite soil.

Keywords: Phytoremediation, Show star grass, Motor oil, Laterite soil, Contamination.