Environmental Engineering Reference
In-Depth Information
Chapter 8
Phytoremediation of Crude Oil-Contaminated
Soil by
Medicago sativa
(Alfalfa) and the Effect
of Oil on its Growth
Saeed Minoui, Dariush Minai-Tehrani and Malak Hossein Shahriari
Abstract
In oil producing countries, crude oil is one of the main organic pollut-
ants of soil and water. The use of plants to phytotreatment of crude oil contami-
nated soil has been a particular interest in environmental cleansing. Some plants
such as grasses and legumes have been demonstrated to have better capacity in
biodegradation of oil in the soil. In this study, the effect of different concentrations
of light crude oil (up to 10 %) on the growth and germination of
Medicago sativa
(alfalfa) was studied. Our results showed that the germination number and the num-
ber of leaves per plant decreased by increasing light crude oil concentration in the
soil. About 75 % of germination was observed in control while it was 15 % in high
concentration of crude oil in soil (10 %). Total dry biomass of plant was higher in
control (2 g) sample while it was lower in 7 and 10 % sample. Number of leaves
was higher in control but it was lower in 7 and 10 % oil-polluted soil. The presence
of high concentration of oil in soil caused chlorosis of leaves and there were no
green plants at the end of experiment (120 days). Total colony and oil-degrading
colony counts in soil showed that in all vegetated samples, the microbial population
was higher than non-vegetated samples. In vegetated samples, the total microbial
population in 7 % samples was higher than control and also higher than that in low
concentrations of crude oil (1 and 3 % samples). The effect of plants on reduction
of oil in soil was also investigated. In all vegetated samples, the reduction of crude
oil was higher than that in non-vegetated samples. The higher reduction occurred
in 1 % sample (70 %), while the lower reduction observed in 10 % sample (20 %).
In conclusion,
Medicago sativa
as a plant in legume family could not tolerate high
concentration of crude oil and crude oil could severely affect its growth and germi-
nation and cause untimely chlorosis. Our results propose that
Medicago sativa
is not
a good option for removal of oil from the soil by the method of phytoremediation.
