Environmental Engineering Reference
In-Depth Information
Fig. 10.3
Reduction of crude
oil after 120 days in different
concentrations of light crude
oil-contaminated soils. (± SD,
n
= 3,
p
< 0.05)
ϬϬϬ
1RQYHJHWDWHG
ϴϬ
9HJHWDWHG
ϹϬ
ΚϬ
ϮϬ
Ϭ
Ϭ
Ϯ
Ρ
ϳ
ϬϬ
&UXGHRLO
was higher that in the non-vegetated soils. In the higher concentrations (7 and 10 %)
the difference in crude oil reduction between the vegetated and the non-vegetated
samples was not significant, while the reduction was significant between the veg-
etated and the non-vegetated samples in concentrations up to 5 %.
4 Discussion
This study focused on assessing the reciprocal effects of light crude oil-contaminat-
ed soil in a potential grass
Festuca arundinacea
(Tall fescue). The reduction in bio-
mass and the length of leaves in high concentration of light crude oil (7 and 10 %)
suggests that the toxic compounds of crude oil in the soil could reduce the number
of germinated seeds and adversely affect the normal growth of roots and shoots in
contaminated vegetated samples. The germination of this plant in 10 % light crude
oil-contaminated soil suggests that the plant could tolerate high concentration of
crude oil (10 %) in the soil. The distribution of fibrous roots of the plant in contami-
nated soil decreased significantly in comparison with the control. The germination
of Tall fescue in 5 % TPH contaminated soil was found to reduce about 70 % of
control (Huang et al.
2005
). Exposure of the plants to tolerable concentrations of
petroleum can cause the chlorosis of the leaves, plant dehydration, stunted growth
and also death (Udo and Fayemi
1975
).
At the end of experiment, the number of green plants decreased in high con-
centrations of light crude oil (5-10 %) which was accompanied by chlorosis and
dehydration. This was in accordance with other studies that have reported the effect
of oil on growth and germination of plants (Merkl et al.
2005
).
Previous reports show that increasing crude oil concentration decreased the mi-
crobial population of the soil (Delille and Siron
1993
). On the contrary, our results
showed that in the presence of high concentration of crude oil (10 and 7 %), the
microbial population and oil degrading bacteria, increased in comparison with the
control and lower concentrations of crude oil (1 and 3 %). This phenomenon might
