International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
1
Petroleum Hydrocarbons Pollution in Soil and its Bioaccumulation in
mangrove species, Avicennia marina from Alibaug Mangrove
Ecosystem, Maharashtra, India*
Sakineh Lotfinasabasl 1*, V.R.Gunale 2 N.S.Rajurkar 3
1,2,3
Department of Environmental Science, University of Pune, Pune 411007, India.
Department of Chemistry, University of Pune, Pune 411007, India.
Email: 1*s.lotfinasab@gmail.com, 2vgunale@hotmail.com, 3rajurkar@unipune.ac.in
3
ABSTRACT
This study was carried out to provide information on the status of contamination with petroleum hydrocarbons in the
mangrove ecosystem of Alibaug, Maharashtra, India and to assess petroleum hydrocarbon phytotoremediation potential of
mangrove species Avicennia marina. Soil and plant sample including leaves, roots and seedlings were collected from eighteen
sites, fifteen from the mangrove area and the rest from Akshi beach along the coast of the Arabian Sea during December the year
of 2010. Samples were analysed for total petroleum hydrocarbons (TPH) using gas chromatograph with flame ionization
detector (FID). The mean level of TPH in the studied samples was found exceed the average global permissible limit in the soil
samples and phytotoxic level in the plant samples .The result showed the level of TPH was in the order Root > Seedling > Leaf
> Surface soil > Depth soil indicating TPH uptake by Avicennia marina. The Bioconcentration Factor (BCF) and Translocation
Factor values proved the potential of using Avicennia marina for phytoremediation to prevent, control and clean up petroleum
hydrocarbons pollutions in the coastal areas.
Keywords : Alibaug mangrove forest; Bioaconcentration factor; Translocation factor; Total petroleum
hydrocarbons;Phytoremediation
1 INTRODUCTION
During the past century, industrialization has increased
the need use of petrochemicals and this, in turn, has resulted
in the contamination of a significant number of area which
have been considerably attracted the attention to organic
pollutant especially petroleum and petroleum byproduct [3].
With the consideration that mangroves are key habitats for
many plants and animals such as fishes and crustaceous in
tropical coastal environment, pollution from anthropogenic
sources especially oil pollutions are important threat to this
ecosystems. Mangrove habitats are often contaminated and
impacted with oil residues and petroleum hydrocarbons
because of their distribution proximity transporting routes
[10].Oil pollution severely damages mangrove ecosystems
[11]. Released petroleum hydrocarbons not only are harmful
for plant itself but also for animals and human being who are
the consumers in the food chain.
If high concentrations of oil or any other pollutant enters
the soil or water supply within mangrove forests, the results
may include death in plant species, change in normal
development, reduced functional ability, and mortality in
birds and fishes that use mangrove habitats for feeding and
breeding grounds [19].
One of the most important organic pollutants is petroleum
hydrocarbons from petroleum product.
Holliger et al. [9] expressed that one of the main cause of
water and soil pollution is the released hydrocarbons into the
Copyright © 2013 SciResPub.
environment whether accidentally or from human activities.
TPH is released to the environment through accidents, from
industries, or as byproducts from commercial or other uses.
As Denys et al. [6] expressed accumulation of TPH in soil
might lead to drastic problem to environmental health.
Hydrocarbon components are categorized into the family of
organic pollutants which are carcinogenic and neurotoxic [5].
Because there are so many, it is not usually practical to
measure each one individually. However, it is useful to
measure the total amount of all hydrocarbons found together
in a particular sample of soil, water, or air. The amount of TPH
found in a sample is useful as a general indicator of petroleum
contamination at that site.
During the past decades it is proved that various plants
along with associated microorganisms have the potential for
the effective and inexpensive cleanup of a broad range of
organic and inorganic wastes from contaminated water, soil,
sediment and air [1], [15],[8], [16], [17], [21], [14].
Phytoremediation is the in situ use of plants and their
associated microorganisms to reduce, clean up and removal of
harmless contaminants from environment [4].
Plants dig their roots into soils, sediments and water, and
roots can take up organic compounds and inorganic
substances and can also stabilize and bind substances on their
external surfaces, and they interact with microorganisms in
the rhizosphere [11]. Uptaken substances may be transported,
International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
stored, converted, and accumulated in the different cells and
tissues of the plant. Finally, aerial parts of the plant may
exchange gases with the atmosphere allowing uptake or
release of molecules [11] (Fig. 1). Mangroves as a critical
habitat in coastal environments can be affected by petroleum
hydrocarbons due to oil spills from physical and toxicological
effects. Physically, one involves suffocation, starvation, or
other physical interference with normal physiological
functions of plants and animals. It is proved that some toxic
substances in the oil especially lower molecular weight such as
aromatic compounds can also kill mangroves which damage
cell membranes in aerial roots. Lighter oils are more acutely
toxic to mangroves than are heavier oils. Alibaug mangrove
forest in the west coast of India is one of most threatened area
by petroleum hydrocarbons due to oil spills. The main species
of mangrove which are found in the Alibaug mangrove forests
are Avicennia marina, Acanthus illicifolius, Aegiceras
cornicuatum, Excoecaria aggaacha, Cerios tagal, Brugeria
cylindrical and Rhizophora mucronota [13]. The present study
was undertaken to assess petroleum hydrocarbon
phytoremediation potential of native mangrove species
(Avicennia marina) in order to prevent, reduce and removal of
petroleum hydrocarbons pollutions from the coastal areas
particularly the mangrove ecosystem of Alibaug, Maharashtra,
India in the proximity of Mumbai.
2
rainfall of 2000 to 2200 mm. The inhabitant mangrove species
are mainly Avicennia marina, Rhizophora mucronota, Cerios
tagal, Acanthus illicifolius, Aegiceras cornicuatum, Excoecaria
aggaacha and Brugeria cylindrical with the stature less than
2.5 m [13].
2.2 Collection of Samples
The soil samples were collected in the morning from the
surface and from 15 cm below the surface from fifteen
sampling sites along the mangrove forest and three from
Akshi beach along the coast of Arabian Sea during October to
December of the year 2010.
Plant samples were collected from the leaf and root of
mangrove species, Avicennia marina, from fifteen sampling
sites along the mangrove forest and three seedling samples
were also taken from the Akshi beach.
2.3 Analysis of Soil / Plant samples for total petroleum
hydrocarbon
According to the Ultrasonic Extraction Method, 3550 of
USEPA [23], previously dried and crushed soil and plant
samples were mixed with anhydrous sodium sulfate until they
resembled free flowing powder and were then mixed with
dichloromethane as a solvent. The soil/plant samples were
sonicated in specified pulse mode. Then the extracted solvents
were poured into a grade-A 100 mL volumetric flask through
a glass funnel that was packed with anhydrous sodium
sulfate. To remove polar nonpetroleum hydrocarbon, silica gel
was added to the sample extracts. The extracts were then
evaporated and concentrated to a higher than the detectable
limit of gas chromatography flame ionization detector
(0.5ppm) with gaseous nitrogen (N2) level of 20 PSI pressure.
The extracted solvent was injected into a GC-FID instrument
for analysis.
2.4 Bioconcentration Factor
The phytoremediation potential of Avicennia marina was
examined by the use of bioconcentration factor.
Bioconcentration factor was computed using the following
formula [2].
.
(1)
Where C biota was the chemical concentrations in the taxa from
this study and C soil was the chemical concentration in the soil.
Fig.1 Petroleum hydrocarbon phytoremediation mechanisms
in plant
2 MATERIAL AND METHOD
2.1 Description of the Study area
Alibaug is in the west coast of India and is situated between
Latitudes 18º 56' N to 18º 29' N and Longitudes 72 º 50' E to 73
º o4' E with a temperature between 38 ºC to 8.4 ºC. The
atmosphere is generally humid and average relative humidity
is over 80% during the southwest monsoon season and in rest
of the year, is between 65% and 75% with an average annual
Copyright © 2013 SciResPub.
2.5 Translocation Factor
Ttranslocation ratio or translocation factor (TF) was calculated
to understand the mobility potential of
petroleum
hydrocarbon from root to leaf. The following formula was
used to calculate the translocation ratio [13].
(2)
Where C leaf is the concentration of TPH in leaf sample and
C root is the concentration of TPH in root sample.
2.6 Statistical analysis
The inter relationship between the concentration of TPH in the
studied samples was determined using Spearman correlation
International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
coefficient (r value). Statistical method of T-test was used to
analyse the concentration of TPH in the surface and depth soil
samples. All the statistical analyse were performed using Minitab
professional 16 statistical software.
3
RESULTS AND DISCUSSION
3.1 Total petroleum hydrocarbon distribution in soil
The concentrations of total petroleum hydrocarbons (TPH) in
the soil and plant samples along with summary of statistical
analysis are shown in Table 1.
Table 1
Concentration and statistical summary of analysed TPH in
the soil
Surface
Depth
and
Site
Leaves
Root
Seedling
Soil
Soil
plant
1
1200
3760
4400
7300
sample
s
2
1440
3680
3600
16300
3
2080
1200
2100
3300
-
4
20800
0.5
2100
2900
-
5
1280
960
4200
3400
-
6
1520
880
2400
4700
-
7
1360
640
2400
5200
-
8
880
880
1400
3700
-
9
960
880
2900
10900
-
10
720
800
4600
3500
-
11
0.5
0.5
0.5
0.5
-
12
720
1200
2100
4300
-
13
720
480
2700
900
-
14
480
640
1900
1800
-
15
560
240
3800
2200
-
16
0.5
1040
-
-
1300
17
1200
1040
-
-
1300
18
640
17040
-
-
8200
Mean
2031.1
1964.4
2706.7
4693.3
3253.3
SD a
4713.3
3900.3
1805.6
4146.3
3983.7
Minb
0.5
0.5
0.5
0.5
1300
Maxc
20800
17040
8200
16300
8200
a:standard deviation b: Minimum c:Maximum
The concentration of TPH in soil surface samples ranged
between 0.5-20800 mg/kg with a mean value of 2031.1 mg/kg.
The result showed the concentration of TPH in the surface soil
of site no 4 was higher than the other sites, indicating that
uptake and accumulation mostly depend on the pollutant
present and its concentration in the environment. This
Copyright © 2013 SciResPub.
3
indicates high content petroleum hydrocarbons remained and
accumulated in this site as a result of petroleum hydrocarbon
effluence. The concentration of TPH in soil samples from
depth ranged between 0.5-17040 mg/kg with a mean value of
1964.4 mg/kg. The highest concentration of TPH was
observed in the depth soil of site no18, which was in the Akshi
coastal area, followed by sites 1 and 2, indicated high content
petroleum hydrocarbon resulting in accumulation of TPH in
the depth soil of this area.
The standard deviation showed the high variation in TPH
concentration of all the 18 sampling sites in case of both
surface and depth soil . Result shows that the concentrations
of TPH in the soil surface samples were higher than the soil
depth samples but the result of T-test statistical method
showed no significant differences between the mean value of
soil surface and depth samples.
These results also show that the mean values of TPH in the
soil samples were higher than the global average permissible
limit of TPH for soil (1000 mg/kg), which indicates the high
concentration of petroleum hydrocarbon pollution in the soil
of study area is mainly due to August 2010 oil spill event.
The variation map of surface soil (Fig. 2a) shows that the
concentration of TPH increased from the north to south of
study area indicating the interaction of seawater with
waterway in the southern part of the mangrove area.
The variation map of TPH in soil of 15 cm depth (Fig. 2b)
shows the concentration of TPH with the highest range,
between 500-1000 mg/kg and increased southwestward up to
3700 mg/kg which indicates a higher concentration of TPH
around the waterway which was observed in the case of
surface soil.
3.2 Total petroleum hydrocarbon distribution in plant
The concentration of TPH in leaf samples ranged between 0.54600 mg/kg with a mean value of 2706.7 mg/kg. The standard
deviation showed moderate variation in TPH concentration in
all the 15 sampling sites. The high concentration of TPH in the
leaf samples showed high petroleum hydrocarbon uptake
capability by leaves of the Avicennia marina. These results
show the mean value of TPH in leaf samples exceeded the
average global permissible limit in soil (1000mg/l) and is
higher than phytotoxic level in the plants (1000-12000 mg/l).
Salanitro et al. [18] have demonstrated that lighter oils have
shown phytotoxic effects at concentrations as low as 1,000–
1,200 mg/kg. It can be concluded that the high concentration
is mainly due to oil spillage.
Variation map (Fig. 3a) showed that the concentration of TPH
in leaf increased (higher than the toxic level) from the East
northward to West southward and the majority of study area
was polluted by petroleum hydrocarbons 2-3 times more than
the phytotoxic level.
TPH concentration in the root samples ranged between 0.516300 mg/kg with a mean level of 4693.3 mg/kg which
indicates higher uptake of petroleum hydrocarbons by roots in
contrast with leaf samples. The standard deviation showed
high variation in TPH concentrations amongst 15 different
sampling sites.
An examination of Table 1 shows that the mean value of TPH
in root samples is about 4.6 times more than average global
International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
TPH permissible limit in the soil and phytotoxic level which
showed high petroleum hydrocarbon pollution in the study
area besides capability of the Avicennia marina to uptake
petroleum hydrocarbon.
The concentrations of TPH in root samples in the majority of
the sampling sites were higher than the soil permissible limit
which indicates high petroleum hydrocarbon pollution .
An examination of Fig. 3b shows that the TPH content of root
samples has an additive trend to southwestward which was
observed in the soil and leaf samples. Fig. 3b also shows a
higher petroleum hydrocarbon uptake in the root samples in
contrast with the leaf samples.
The high concentration of TPH in seedling samples with a
mean value of 3253.3 is indicative of petroleum hydrocarbon
uptake by immature plant of Avicennia marina as well.
Generally the concentration of TPH in plant samples was
observed in the order: root> seedlings > leaves. The
comparison of TPH content in the plant samples shows that
there is a good uptake of TPH through root, leaf and seedling
samples of Avicennia. This results in higher concentration of
TPH in the root than in the leaf samples indicating more
4
petroleum hydrocarbon pollution in the soil and transferred
toward plant tissue. The roots of Avicennia marina are having
more uptake of petroleum hydrocarbons through
phytostabilization
and,
rhizidegradation
mechanism.
Phytostanilisation immobilize contaminants in the soil
through the absorption and accumulation into the roots, the
adsorption onto the roots, or the precipitation or
immobilization within the root zone. These chemical
contaminants then are rendered into a stable form. In
Rhizodegradation contaminants will be degraded in the soil
through the bioactivity that can be produced and exuded by
plants or from soil organisms such as bacteria, yeast, and
fungi. A study was carried out by authors which proved that
the isolated fungi from the soil of the study area are capable of
biodegradation of petroleum hydrocarbons [7].
The lower concentration of TPH in leaf samples may have
been caused due to phytodegradation or phyto transformation
of petroleum hydrocarbons which was subjected the
contaminants to the bioremedial processes occurring within
the areal part of plant itself.
Fig. 2 Variation map of TPH concentration in the surface (a) and depth soil (b)
Fig. 3 Variation map of TPH concentration in the leaves (a) and root (b)
3.3 Correlation Matrix
The relationship between the concentration of TPH in soil
and plant samples was examined using correlation analysis
(Table 2). The Pearson correlation showed a significant and
Copyright © 2013 SciResPub.
positive relation (r= 0.74, p=0.002) (significant level a t P <
0.05) between the TPH concentration in depth soil and root.
This is attributed to an increase of TPH in soil which further
increases the uptake of petroleum hydrocarbons by the plant.
International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
A linear regression between TPH concentration in depth soil
and root (Fig. 4) revealed a linear model which described the
relationship as:
(3)
Where Y is Concentration of TPH in root and X is the
concentration of TPH in soil.
Table 2
Correlation coefficient matrix of TPH between soil and
plant samples
Sample
Surface Soil
Depth Soil
Leaves
Surface Soil
Depth Soil
Leaves
1
-0.221
-0.233
*
1
0.021
*
*
1
Root
-0.077
0.742
-0.112
p value=0.002 at significant level of p < 0.05
Fig. 4 Linear regression between TPH concentration
in depth soil
and root
3.4 Bioconcentration and Translocation factors
The bioconcentration factor (BCF) and Translocation factor
(TF) values of TPH in leaf, root and seedling samples are
shown in Table 3 and Fig. 5. The BCF value of TPH was
observed greater than 1, in the three type of plant samples
indicative of petroleum hydrocarbon uptake from soil through
the root. Generally the BCF value of TPH was observed in the
order: Root > Leaf > seedling indicating phytoremediation
potential of Avecina marina through phtostabization in root
and phytodegradation in leaf samples. The higher BCF vale of
in root samples indicates that the remediation of petroleum
hydrocarbons contamination by Avicennia marina has been
mostly done via the phytostabilisation mechanism.
The mean level of translocation factor of TPH in plant
samples was found to be lower than 1.
The lower TF value of leaf samples shows uptake of
hydrophilic compound of petroleum hydrocarbons by root
and translocation to the leaf through vascular system. In
general, chemicals that are highly water soluble are not
sufficiently sorbed to roots or actively transported through
Copyright © 2013 SciResPub.
5
plant membranes [20].
Hydrophobic chemicals are generally not sufficiently
soluble in water or are bound so strongly to the surface of the
roots and may not pass beyond the root’s surface due to the
high proportion of lipids present at the surface, so can not be
easily translocated into the plant [22].
Table 3
Bioconcentration (BCF) and translocation factor (TF) values
of TPH in leaf, root and seedling samples
site
Leaves
BCF
Root
Translocation
seedling
Ratio
1
1.8
2.9
0.6
2
1.4
6.4
0.2
3
1.3
2.0
0.6
4
0.2
0.3
0.7
5
3.8
3.0
1.2
6
2.0
3.9
0.5
7
2.4
5.2
0.5
8
1.6
4.2
0.4
9
3.2
11.8
0.3
10
6.1
4.6
1.3
11
1.0
1.0
1.0
12
2.2
4.5
0.5
13
4.5
1.5
3.0
14
3.4
3.2
1.1
15
9.5
5.5
1.7
16
2.5
17
1.2
18
0.9
Mean
2.9
4.0
1.5
0.9
a
SD
2.4
2.8
0.8
0.7
b
Min
0.2
0.3
0.9
0.2
Max c
9.5
11.8
2.5
3.0
a:standard deviation b: Minimum c:Maximum
Fig. 5 Bioconcentration and translocation factor of TPH in seedling,
leaf and root samples
International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
Variation maps of BCF in root and leaves of Avicennia
marina in the study area (Fig. 6a and Fig. 6b) show that BCF
values of TPH in leaves in northern part of the study area are
higher than other part and decreased towards southern part
unlike of BCF values in roots. This indicates that southern
part of study area close to waterway polluted by petroleum
hydrocarbons which are lighter and more hydrophilic such as
lighter aromatic and aliphatic hydrocarbons including
benzene, toluene, ethylbenzene, xylenes (BTEX ) and n-hexane
6
respectively.
Variation of TF values which are shown in Fig. 6c indicate
that Avicennia marina is capable of removal of Petroleum
pollution through the leaves and roots and translocation of
chemicals. This not only depends on the type of plant but also
on the concentration of pollutant and the type and nature of
the chemical.
Fig. 6 Variation map of bioconcentration and translocation factor of TPH in the
leaves and root of the study area
4
CONCLUSION
The result of present study explored the potential of
mangrove species, Avicennia marina for bioaccumulation of
petroleum hydrocarbons from contaminated soil either on the
surface or in the lower layer of soil. The high concentrations of
TPH in the soil and plant samples is indicative of pollution by
petroleum hydrocarbons in the mangrove forest of Alibaug.
The results show that there are differences between the
concentration of TPH in leaves, roots and seedlings of
Avicennia marina indicating higher uptake of petroleum
hydrocarbons by roots followed by seedlings and leaves. The
higher BCF factor for root showed that phytoremediation
occurs mostly through phytostabilisation.
Since phytoremediation has been identified as a cost
effective, environmentally friendly, aesthetically pleasing
process for removal of environmental pollutants Avicennia
marina is found to be a potential species for protection of
coastal ecosystem.
ACKNOWLEDGEMENT The authors would like to
Copyright © 2013 SciResPub.
acknowledge the University of Pune for providing all
necessary facilities for completion and smooth conduct of the
work.
REFERENCES
[1] Aprill W, Sims RC (1990) Evaluation of the use of
prairie grasses for stimulating polycyclic aromatic
hydrocarbon treatment in soil. Chemosphere 20 (1-2):
253-265
[2] Agoramoorthy G, Chen F, Hsu MJ (2008) Threat of
heavy metal pollution in halophytic and mangrove
plants of Tamil Nadu, India. Environ Pollut 155 : 320326
[3] Bauman B (1991) Research needs: motor fuel
contaminated soils. Hydrocarbon Contaminated Soils.
Calevrese EJ and Kostecki PT. Lewis Publishers,
Chelsea, MI, 41-56.
[4] Cunningham SD, Anderson TA, Schwab AP, Hsu FC
(1996) Phytoremediation of soils contaminated with
International Journal of Advancements in Research & Technology, Volume 2, Issue2, February-2013
ISSN 2278-7763
organic pollutants. Advances in Agronomy 56: 55-114
[5] Das N, Chandran P (2011) Microbial degradation of
petroleum hydrocarbon contaminants: An overview.
Biotechnol Res Int DOI: 10.4061/2011/941810
[6] Denys S, Rollin C, Guillot F, Baroudi H (2006) In-situ
phytoremediation of PAHs contaminated soils
following a bioremediation treatment. Water Air Soil
Pollut 6: 299-315
[7] Lotfinasabasl S, Gunale VR, Rajurkar NS (2012)
Assessment of Petroleum Hydrocarbon Degradation
from Soil and Tarball by Fungi. Bioscience Discovery
3(2):186-192
[8] Medeiros PM, Bicego MC, Castelao RM, Rosso CD,
Fillmann G, Zamboni AJ (2005) Natural and
anthropogenic hydrocarbon inputs to sediments of
Patos Lagoon Estuary. Brazil Environ Int 31: 77–87
[9] Holliger C, Gaspard S, Glod G, Heijman C,
Schumacher W, Schwarzenbach RP, Vazquez F (1997)
Contaminated environment in the subsurface and
bioremediation: Organic contaminants. FEMS
Microbiolo Reviews 20(3-4): 517 – 523
[10] Hoff R, Hensel P et al (2002) Oil Spills in Mangroves,
National Oceanic and Atmospheric Administration.
NOAA Ocean Service, Office of Response and
Restoration. Washington
[11] Marmiroli N, Marmiroli M, Maestri E (2006)
Phytoremediation and phytotechnologies: A review
for the present and the future. In: Twardowska I,
Allen HE,Haggblom MH (ed). Soil and water
pollution monitoring, protection and remediation.
Springer, Netherland
[12] Mastaller
M (1996) Destruction of mangrove
wetlands- causes and consequences, Nat Resour Dev
43(44): 37-57
[13] Pahalawattaarachchi V, Purushothaman C S, Vennila
A (2009) Metal phytoremediation potential of
Rhizophora mucronata (Lam.). Indian J Mar Sci
38(2): 178–183
[14] Pradhan SP, Conrad J R, Paterek JR, Srivastava VJ
(1998) Potential of phytoremediation for treatment of
PAHs in soil at MGP sites. J soil Contam 7(4): 467-480
[15] Qiu X, Leland TW, Shah SI, Sorensen DL, Kendall EW
(1997) Field study: Grass remediation for clay soil
contaminated with polycyclic aromatic hydrocarbons.
In American Chemical Society Symposium Series;
Phytoremediation of soil and water contaminants
pp186-99
[16] Reilley KA, Banks M K, Schwab AP (1996) Organic
chemicals in the environment: dissipation of
polycyclic aromatic hydrocarbons in the rhizosphere.
J Environ Qual 25: 212-219
[17] Reynolds CM, Wold DC, Gentry TJ, Perry LB,
Copyright © 2013 SciResPub.
7
Pidgeon CS, Koenen BA, Rogers HB, Beyrouty CA
(1999b) Plant enhancement of indigenous soil microorganisms: a lowcost treatment of contaminated soils.
Polar Record 35: 33-40
[18] Salanitro JP, Dorn PB , Huesemann MH, Moore KO,
Rhodes IA, Rice Jackson LA, Vipond TE, Western
MM, Wisniewski HL. 1997. Crude oil hydrocarbon
bioremediation and soil ecotoxicity assessment,
Environ Sci Technol 31: 1769-1776.
[19] Samarasekara VN (1994) The impact of agriculture
and industry on a wetland ecosystem: The case of
Koggala Lagoon, Sri Lanka. Coastal Manage Trop
Asia 3: 15-19
[20] Schnoor JL, Licht LA, McCutcheon SC, Wolfe NL,
Carreira LH (1995) Phytoremediation of organic and
nutrient contaminants. Environ Sci Technol 29 (7):
318-323
[21] Schwab AP, Banks MK, Arunachalam M (1995)
Biodegradation of polycyclic aromatic hydrocarbons
in rhizosphere soil. Bioremediation of Recalcitrant
Organics. Hinchee RE, Anderson DB, Hoeppel RE.
Battelle Press, Columbus, pp 23–29
[22] Siciliano SD, Germida JJ (1998b) Mechanisms of
phytoremediation: biochemical and ecological
interactions between plants and bacteria. Environ
Review 6: 65-79
[23] US EPA Method 3550 B (1996) Ultrasonic extraction
methods for evaluating solid waste. EPA Report SW846, USA, Chapter 5.