International Journal of Marine Science, 2017, Vol.7, No.6, 51-58
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Table 2 Seasonal variations of Total Petroleum Hydrocarbons (µg/g) dry weigh with mean in soil samples of West Qurna-2 oil field
Station
Summer
Autumn
Winter
Spring
R. Mean
SD
±
1
15.33
16.38
20.10
14.82
16.657
2.385
2
17.34
18.04
20.53
16.99
18.225
1.597
3
17.77
18.88
22.42
20.81
19.97
2.060
4
23.14
24.22
26.76
22.43
24.137
1.896
5
24.87
24.99
32.23
25.66
26.937
3.545
6
23.58
24.36
28.28
22.77
24.747
2.442
7
27.07
27.86
35.63
27.82
29.595
4.039
8
29.59
30.63
38.45
34.01
33.170
3.993
9
29.59
30.67
38.98
39.07
34.577
5.154
10
33.39
34.03
40.21
41.86
37.372
4.290
S. Mean
24.167
25.006
30.359
26.624
-
-
Note: R. Mean= regional mean, S. Mean= seasonal mean
The seasonal distribution of TPHs show that the highest level in all stations was recorded during winter (30.350
μg/g) and the lowest levels was during summer (24.167 μg/g), while spring was (26.624 μg/g) and autumn
(25.006 μg/g) (Figure 3; Table 2), the seasonal concentration arrange as following: winter > spring> autumn>
summer. This result was in agreement with (Douabul et al., 2012) and (Al-Hassen, 2011) who found that the
concentrations of total hydrocarbons were higher in winter than summer, this can point largely to role of which
played the climatic conditions. During winter, soil temperature declined due to the declining of air temperatures,
this acts as slow down the evaporation process of fluids from the soil surface and ground. Since increase in soil
moisture during this season (as a result of rainfall, groundwater table rise, seepage, low rate of evaporation, etc.)
also acts as rise to absorption ability between soil particles and fluid molecules, then hydrocarbons will extend
during the winter more than summer. It is during the summer season, violate organic compounds expose to a
further urgent evaporation as a consequence of elevated air temperatures (Al-Hassen, 2011).
Al–Saad (1995) reported that the concentrations of total hydrocarbons during winter was greater than in summer
because of the more extensive event of combustion processes with large amount of fossil fuel utilized as a part of
family warming during the cold season as well as the higher association of these hydrocarbons with atmospheric
particles at lower ambient temperature.
The most important factor governing the removal of hydrocarbons in the environment by evaporation was
temperature (Wang et al., 2005). Also the favors microbial degradation process was increase by temperature
(Coulon et al., 2007). The components of oil was degraded by photo-oxidation (Garrett et al., 1998). The intense
solar radiations combined with relatively high temperature were the characteristic features of the climate of the
subtropical regions of Iraq. Temperature and photo–oxidation could account for rather low levels of hydrocarbons
encountered in the area, especially during summer (Farid et al., 2014).
Grain size of collected soil from the studied station can be classified as silty sand and sandy silt texture. There were
non-significant correlation between the TPHs in soil and all of the soil texture compounds (sand, silt and clay). This
result was in agreement with (Al-Hejuje, 2014).
Total organic carbon (TOC), concentration of various classes of hydrocarbons and diagnostic parameters at each soil
sampling site are outlined in (Table 3). A significant correlation was observed (p≥0.01) between the percent of Total
Organic Carbon and total petroleum Hydrocarbons (r=0.814). This result was in agreement with (Al-Mahana,
2015).
If we compared our data with other study, we find that the data are within the range as shown in Table 4.
