International Journal of Marine Science 2015, Vol.5, No.52: 1-8
3
previously extracted with methylene chloride for 36
hours, dried at 130 °C for 24 hours, and deactivated
with deionized water. The extract was applied to the
head of column. The first fraction containing the
aliphatic hydrocarbons was eluted from column with
n
-hexane and the second with benzene. The second
fraction saved for further analysis and the composition
of only the first fraction will be discussed. After most
of the solvent was removed from the
n
-hexane
fraction, the sample was then analyzed in a Allegent
capillary gas chromatography (GC) in which the
helium gas was used as a carrier gas with a linear
velocity of 1.5 ml minutes
−1
. The operating temperatures
for detector and injector were 350°C and 320°C,
respectively. The silica capillary column was operated
under initial, final and rate temperatures that
programmed as follows: Initial temperature was 60°C
for 4 min while final temperature was 280°C for 30
min and rate was 4°C/ minutes.
Quantification of peaks and identification of
hydrocarbons were done by computing integrator.
Unresolved Complex Mixture (UCM) was measured
using planimetry. The Odd and Even
n
-alkane
Predominance Index (OEPI) and the Carbon Preference
Indices (CPI) were used to indicate the general source
of hydrocarbons whether their origin was biogenic or
anthropogenic (Askari and Pollard, 2005; Zrafi et al.,
2013). Pristane/Phytane ratio and the Unresolved
Complex Mixture index (UCM) were used as indicators
of petroleum contamination (Tolosa et al., 2005; Wang
et al., 2011) and to estimate the degree of bacterial
degradation (Punyu et al., 2013).
For quality assurance, the laboratory blank and spiked
matrix (internal standard spiked into soil) was analyzed.
Results showed that there were no significant background
interferences. Recovery assays for standards aliphatic
compounds ranged from 85% to 91%. Standard
deviation for the method was less than 10 % based on
replicate analysis. All concentrations were expressed
on a soil dry weight basis.
Results and Discussion
The average concentrations of total
n
-alkanes in soils
of Basrah city and the
n
-alkanes calculated indies are
listed in Table (2, 3, 4 and 5). The concentrations
ranged between 3.575 and 21.266 µg g
-1
dry weight,
with an overall average of 9.152 µg g
-1
dry weight.
Insufficient documentation exists for total
n
-alkanes
content in Basrah city soils. Results obtained from the
present study show that samples taken from the soils
of stations Ras-Al-Bisha, Al-Qurna, Al-Seeba, Garmat
Ali, Abu Al-Khasib, Saffwan, Al-Daer, Al-Tanoma,
and Al-Zubair displayed relatively low values of total
n
-alkanes, ranging from 3.575 to 5.467 µg g
-1
dry
weight. These low total
n
-alkanes concentrations may
be regarded as the natural background levels in these
areas. Relatively high concentrations of total
hydrocarbons (10.88 to 21.266 µg g
-1
dry weight)
were found in those soils collected from stations of
Al-Rumella, Al-Shiabah, Al-burjsia, Kor-Al-Zubairand,
Center of Basrah, Al-Fao, and Um-Qasir which
associated with discharges of petroleum wastes. For
example, sampling stations Al-Rumella, Al-Shiabah,
Al-burjsia, and Kor-Al-Zubair hosted the largest oil
refineries, gas production plant and petrochemical
factory as well as these stations represented the sites
of crude oil extraction and production (oilfields).
Station Center of Basrah received petroleum wastes
from houses and workshops activities, gasoline
stations, transportation and industries activities,
electrical generating plants and units, leakages from
tanks or tanker trucks and dump of waste petroleum
by-products on soils. Al-Fao and Um-Qasir ports are
stations suspected to be influenced by oil exportation.
Figure (2) shows the spatial concentrations profiles of
total
n
-alkanes among different sampling stations.
The concentrations of total
n
-alkanes in soils from 16
sites varied from season to season (Table 5 and Figure
3), showing a decreasing order of winter (average=
12.587 μg g
-1
) > autumn (average= 10.054 μg g
-1
) >
spring (average= 7.416 μg g
-1
) > summer (average=
6.552 μg g
-1
), with the winter season being the highest.
Williams et al., (2006) reported that temperature
represents one of the most important factors limited
the rates of hydrocarbons microbial degradation in the
winter. It is possible that the weather impacted the
activities of the microorganisms in the soils, which
degrade the hydrocarbons. The high temperature
seemed to offer the best environmental conditions to
support the highest rates of hydrocarbons biodegradation.
During the warmer months, hydrocarbons biodegradation
is rapid while during the colder month the biodegradation
process is less efficient. Hence, biodegradation was
