Environmental Engineering Reference
In-Depth Information
1 Introduction
Soil pollution with crude oil is a global disaster. It is a common phenomenon in
oil bearing and industrial countries (Merkel et al.
2004a
,
b
). There are several soil
cleaning methods including burning, washing, chemical and physical treatments
and also bioremediation (Garcia et al.
2000
). Bioremediation is use of plants, mi-
croorganisms or both to remove or detoxify environmental contaminants. This
phenomenon has been intensively studied during the past two decades, because of
the need for a low-cost,
in-situ
alternative to more expensive technologies (Merkel
et al.
2004a
,
b
; Chehregani and Malayeri
2007
; Chehregani et al.
2008
). In petro-
leum-polluted conditions, applying plants or microorganisms or their combinations
can help to convert hydrocarbons to non-toxic forms (Cunningham et al.
1996
).
Bioremediation has been applied for soil cleaning from crude oil (Wiltse et al.
1998
;
Radwan et al.
1998
; Merkel et al.
2005
), motor oil (Dominguez-Rosado and Pichtel
2004
), and diesel fuel pollution (Chaineau et al.
2000
), but the removal efficiency is
highly variable and is related to applied organism potency and environmental con-
ditions (Angehrn et al.
1998
). Since bioremediation of crude oil-contaminated soils
is mainly due to biodegradation by the microbial populations that are associated
with the rhizosphere of plants, or are associated and attached with roots, the root
system of the plants play an important role (Frick et al.
1999
; Mohsenzadeh et al.
2009
). Plants can influence degradation of oil indirectly by changing the physical
and chemical conditions of the soil (Cunningham et al.
1996
). Roots exude organic
and inorganic substances to its surroundings during normal metabolism, which act
as nutrients for soil microorganisms, thus increasing the degradation of toxic or-
ganic chemicals (Anderson et al.
1993
).
It has been shown that some tropical grasses and legumes are also resistant to
crude oil pollution and root surface increases in some graminoid plants including
Brachiaria
brizantha
,
Cyperus aggregatus
and
Eleusine
indica
under polluted soil
condition (Merkel et al.
2005
).
The microorganisms are economically and environmentally important because
they help in the remediation and rehabilitation of oil-polluted soils (Yateem et al.
1997
; Eggen and Majcherczykb
1998
; Nicolotti and Egli
1998
, Obuekwe et al.
2005
; Dritsa et al.
2007
; Friedrich et al.
2007
). Some researches have shown that
some fungal species are resistant to petroleum pollutants and they are capable of
removing soil pollutants. The keratinolytic fungi, especially
Trichophyton ajelloi
have been shown as a potential tool for assessment of soil petroleum hydrocarbon
pollution and associated bioremediation progress (Ulfig et al.
2003
). Some fungal
strains namely
Alternaria alternate
,
Aspergillus flavus
,
Curvularia lunata
,
Fusar-
ium solani
,
Mucor racemosum
,
Penicillium notatum
and
Ulocladium atrum
were
isolated from the soils in the oil- polluted areas in Saudi Arabia (Hashem
2007
).
Eggen and Majcherczykb (
1998
) showed that white rot fungus,
Pleurotus ostreatus,
could remove polycyclic aromatic hydrocarbons (PAH) in polluted soil (Eggen and
Majcherczykb
1998
). Little attention has been paid to the role of plant root as-
sociated fungal species in the environmental biotechnology and bioremediation of
petroleum pollution, especially in Middle East region (Yateem et al.
1999
; Hashem
2007
).
