PHYTOREMEDIATION OF CRUDE OIL CONTAMINATED SOIL USING VETIVER GRASS
(Chrypsopogon zizanioides).
Abstract
Environmental pollution is generally caused by two main factors that
include high rate of industrialization and rapid increase in population
thereby putting more pressure on natural resources such as petroleum. As
a result the petroleum industry affects the environment through oil
spills causing many negative effects on human health and the surrounding
ecosystem due to presence of toxic compounds in crude oil such as the
Polycyclic Aromatic Hydrocarbons (PAHs) that is potentially carcinogenic
to humans. The aim of this research is to investigate the efficiency of
Chrypsopogon zizanioides also known as vetiver grass with the aid of bio
surfactants and N.P.K. fertilizer in dissipating and containing organic
pollutants in the soil. It is specifically focused on the 16 Polycyclic
Aromatic Hydrocarbons (PAHs) classified by United States Environmental
Protection Agency (US EPA) as priority pollutants. The general
methodology involved a glasshouse experiment by growing the plant C.
zizanioides in a freshly spiked oil contaminated soil and a weathered
hydrocarbon contaminated soil from where the soil samples were treated
with ramphnolipids including (95% (Mono-Rhamnolipid dominant) and 95%
(Di-Rhamnolipid dominant) produced by Pseudomonas aeruginosa and N.P.K.
fertilizer to promote plant and the microbial biomass. Some of the
control samples were left uncontaminated (oil free) while others were
left unplanted (plant free) to investigate the growth of the plant in
the absence of oil and the fate (degradation) of crude oil in the
absence of the grass. Thereafter, soil samples were collected
periodically on monthly basis and the concentration of PAHs was assessed
in the laboratory via Gas Chromatography Mass Spectrometry (GC MS). The
result of this research has already indicated an improvement in plant
and microbial biomass in all the samples treated with N.P.K. fertilizer
and rhamnolipids after a period of 72 days. More plant culms and heights
were observed to have emerged in samples treated with N.P.K. fertilizer
only followed by samples treated with N.P.K. and biosurfactants.
Furthermore, there has been a reduction in the concentration of the PAHs
in the crude oil contaminated soils as a result of the combined action
of C. zizanioides, ramphnolipids and N.P.K. fertilizer as compared to
the control samples. It also highly anticipated that C. zizanioides may
help in breaking down the PAHs in the weathered hydrocarbon contaminated
soil.