Environmental Engineering Reference
In-Depth Information
(Garcia et al.
2000
). Bioremediation is use of plants and microorganisms to remove
or detoxify environmental contaminants. It has been intensively studied over the
past two decades, driven by the need for a low-cost,
in-situ
alternative to more ex-
pensive engineering-based remediation technologies (Merkel et al.
2004a
; Chehre-
gani and Malayeri
2007
; Chehregani et al.
2008
). In petroleum polluted conditions,
plants or plant associated microflora can convert hydrocarbons (HCs) to non-toxic
forms (Cunningham et al.
1996
). Bioremediation has been applied to remove crude
oil (Wiltse et al.
1998
; Radwan et al.
1998
; Merkel et al.
2005
), motor oil (Domin-
guez-Rosado and Pichtel
2004
) and diesel fuel (Chaineau et al.
2000
) from soil but
the removal efficiency is highly variable (Angehrn et al.
1998
). Since bioremedia-
tion of petroleum-contaminated soils is mainly based on biodegradation by the fun-
gal strains that are present in the rhizosphere of plants (Mohsenzadeh et al.
2009
)
or are associated and attached with roots (Frick et al.
1999
), the root system of the
plant is one of the most important factors. Plants can indirectly influence degrada-
tion by altering the physical and chemical conditions of the soil (Cunningham et al.
1996
). Many organic and inorganic substances are exuding from the plant roots
during normal metabolism. These root exudates act as substrates for soil microor-
ganisms, thereby enhancing the degradation of toxic organic chemicals (Anderson
et al.
1993
).
Merkel et al. (
2005
) have shown that some tropical grasses and legumes are re-
sistant to petroleum pollution and root surface showed an increase in the graminoids
namely
Brachiaria
brizantha
,
Cyperus aggregatus
and
Eleusine
indica
in petro-
leum polluted soils.
There are different economically and environmentally important uses of micro-
organisms, one of these being remediation and rehabilitation of petroleum contami-
nated soils (Eggen and Majcherczyk
1998
; Yateem et al.
1997
; Nicolotti and Egli
1998
; Obuekwe et al.
2005
; Dritsa et al.
2007
; Friedrich et al.
2007
). Some prior
researches have shown that some fungal species are resistant to petroleum and oil
derived pollutants and they are capable of cleaning soil pollution. The results of
Ulfig et al. (
2003
) depict that keratinolytic fungi, specially
Trichophyton ajelloi,
are a potential tool for assessment of soil petroleum hydrocarbon contamination
and associated bioremediation process. Fungal strains namely
Alternaria alternate
,
Aspergillus flavus
,
Curvularia lunata
,
Fusarium solani
,
Mucor racemosum
,
Peni-
cillium notatum
and
Ulocladium atrum
have been isolated from the soils in the
petroleum polluted areas in Saudi Arabia (Hashem
2007
). Eggen and Majcherczyk
(
1998
) showed that white rot fungus,
Pleurotus ostreatus
could remove polycyclic
aromatic hydrocarbons (PAH) in contaminated soil. According to Seker and Öztürk
(
2006
) white rot fungi can very well be utilized for the decolorization of highly
contaminated waste waters. Little attention has been paid to the role of plant root
associated fungal species in the environmental biotechnology and bioremediation
of petroleum pollution, especially in Middle Eastern region (Yateem et al.
1999
;
Hashem
2007
).
Numerous sites are contaminated globally with crude or refined oil in differ-
ent countries. Iran as a one of the major oil producing countries faces the same
situation. For bioremediation purposes we have to think first about the ecological
