International Journal of Geosciences, 2011, 2, 562-572
doi:10.4236/ijg.2011.24059 Published Online November 2011 (
Copyright © 2011 SciRes. IJG
Assessment of the Moroccan Mediterranean Coasts
Contamination by Hydrocarbons (Non Aromatic
Hydrocarbons, Aromatic Hydrocarbons
and Linear Alkylbenzenes)
Saida Bouzid1*, Soumaya Khannous1, Ioanna Bouloubassi2, Alain Saliot2, Hassan Er Raioui1
1Equipe Géosciences et Environnement, Département des Sciences de la Terre, Faculté des Sciences et Techniques à
Tanger, Ancienne route de laviation, Tanger, Maroc
2LOCEAN-IPSL, UMR 7159, CNRS/IRD/UPMC/MNHN, Université Pierre et Marie Curie, Paris, France
Received April 6, 2011; revised August 16, 2011; accepted September 28, 2011
In order to evaluate the contamination of the Moroccan Mediterranean coasts by persistent organic pollutants
we studied hydrocarbons and linear alkylbenzenes in bivalve tissues (cockles) collected seasonally from sev-
eral points along the western Moroccan coasts in the Mediterranean Sea. Two fractions corresponding to non
aromatic and aromatic hydrocarbons were analyzed by GC/FID and GC/MS. Non aromatic hydrocarbon
concentrations vary in the range of 24.1 - 2731 μg/g dry weight (dw) while total n-alkanes vary from 2.2 to
68.2 μg/g. Few exceptions were noted with values up to 243 μg/g (dw), which is high compared to other
Mediterranean sites. The presence of an important unresolved complex mixture (UCM) indicated a signifi-
cant petroleum contamination, confirmed by the identification of 17α(H), 21β(H) hopanes. Biogenic contribu-
tions were also detected within the n-alkane distribution (n-C17, n-C18, n-C27, n-C29, n-C17/Pr, n-C18/Ph) and
by the presence of alkenes. C13 and C14 linear alkylbenzenes were found at concentrations of 478 - 1954 ng/g.
and point to pollutant inputs from wastewaters. Polycyclic aromatic hydrocarbons were present in low con-
centrations below the GC detection limit. The observed seasonal and spatial variations were linked to the
magnitude of inputs from marine and land-based pollutant discharges.
Keywords: Western Moroccan Mediterranean Coast, Bivalves Contamination, Gas Chromatography,
Hydrocarbons, Biogeochemical Markers, Petrogenic and Biogenic Origins
1. Introduction
Among persistent organic pollutants, hydrocarbons are
the most ubiquitous organic contaminants in the marine
environment, often at a high level in areas submitted to
intense ship traffic and in semi-enclosed seas [1]. In the
Mediterranean Sea, Burns and Saliot [2] estimated that
over three quarters of a million tonnes of oil were intro-
duced annually into the Mediterranean Sea from land-
based and open-sea discharges. Compared with updated
estimates of oil inputs to the world’s oceans [3], the
Mediterranean would receive about 24% of the NAS
“best reasonable estimate”, although representing about
1% of the world’s ocean surface.
Many studies of petrogenic and pyrolytic hydrocarbon
contamination have been carried out in the northwestern
Mediterranean coasts, especially in sediment and biota
samples [4-7]. But there is a tremendous lack of informa-
tion regarding the southern Mediterranean, except for the
Algerian [8], Tunisian [9,10] and Egyptian coasts [11].
The western Moroccan Mediterranean coasts have been
investigated by a preliminary study [12], which remains
very incomplete. These coasts are well known for tour-
ism, fisheries and industrial activities. They receive high
inputs of organic matter mostly anthropogenic, from ship
traffic discharges, untreated sewage and wastewater dis-
charges. But the level of contamination is still unknown.
The MYTILOS project, initiated in 2003 (for a duration
of 3 years), was focused on the realization of a surveil-
lance network of onshore waters of the western Mediter-
Copyright © 2011 SciRes. IJG
ranean Sea using mussels as transplanted bioindicators. It
was dealing with chemical pollutant analysis, mainly of
polycyclic aromatic hydrocarbons (PAH). The latter ap-
peared to be important in Spanish (Valence) and Italian
(Piombino) coasts.
However, the results remain limited especially for the
Moroccan Mediterranean coasts. The project had been
extended with a new project (2006) INTERREG III B
MEDOC. Nevertheless, there is still a lack of informa-
tion regarding the Moroccan Mediterranean coasts since
this new project concerns mainly Italy, Greece, Tunisia,
Lebanon and Syria.
The study of the Moroccan Mediterranean coasts re-
quires a species of bivalves having an important geo-
graphic repartition and serving as a good indicator such
as cockles, Acanthocardia tuberculata. This explains the
aim of our study, focusing on hydrocarbons and alkyl-
benzenes, and using Acnathocardia Tuberculata as a
good biological indicator having an important geo-
graphic repartition.
In general, bivalves are widely used for monitoring
pollution in the marine environment [13,14]. They are
considered as the best bioindicators of micropolluants
because of their ability to concentrate various contami-
nants to levels well above those present in the surround-
ing waters or sediment [15]. Moreover, they provide in-
formation on local pollution sources.
In order to reach our objectives, various series of hy-
drocarbon compounds (n-alkanes, isoprenoid hydrocar-
bons, unsaturated hydrocarbons, hopanoids, alkylben-
zenes) were analyzed by gas chromatography-flame ioni-
zation detection (GC/FID) and gas chromatography-mass
spectrometry (GC/MS). Seven stations were selected
along the western Mediterranean coasts of Morocco, from
F’nideq to Kaâ Srass. Cockles were collected at different
periods of the year, including dry and humid seasons.
This study permits to assess the level of contamination
by hydrocarbons along the western Mediterranean coasts
of Morocco and to compare with data obtained in other
sites both in north and south western Mediterranean sites.
2. Materials and Methods
2.1. Study Area and Sampling
The littoral between F’nideq (35˚51'05N; 5˚21'00W) and
Kaâ Asrass (35˚25'00N; 5˚04'00W) was chosen for this
study (Figure 1).
Along the northern part of these coasts, there is a chain
of tourism installations with 2 pleasance harbours (Ma-
rina Smir and Marina Kabila) and one fishery harbour
(M’diq port). This coastal zone is subjected to important
inputs from sewage waters from Tetouan city (2 470 372
habitants in the region, 213.52 hab/km²) and close vil-
lages. It is important to indicate the significant role of
some rivers like Martil (0.23 - 3350 m3/s respectively on
summer and winter season) and Oued Laou (2.30 - 2150
m3/s respectively on summer and winter season), in the
drainage of industrial and domestic discharges to the
marine environment.
Four campaigns were realised to collect samples of
lected from 6 sites in spring (S1-A, S3-A, S4-A, S5-A,
Figure 1. Map of the northwest coast of Morocco showing sampling locations. (Fq: Fnideq city, Rs: Restinga village (pleas-
ance harbor), Mq: M’diq city (Fisheries and pleasance harbor), Mr: Martil city (river mouth), OL: Oued Laou village, OL.R:
Oued Laou River (river mouth), Ksr: Kaâ Sras village.
Copyright © 2011 SciRes. IJG
S6-A, S7-A), from 7 sites in summer (S1-B, S2-B, S3-B,
S4-B, S5-B, S6-B, S7-B), from 6 sites in autumn (S1-C,
S2-C, S4-C, S5-C, S6-C, S7-C), and from 5 sites in win-
ter (S3-D, S4-D, S5-D, S6-D, S7-D) (Figure 1).
2.2. Extraction and Analysis of Hydrocarbons
Entire organism tissues were crushed, freeze-dried and
soxhlet extracted (5 g) with methanol for 10 h. Per-
deuterated internal standards (n-C24D50 and p-terphenyl-
D14) were added before the extraction. The saponification
of the lipid extract was performed with KOH/distilled
water (0.7N) for 2 h. Afterwards, liquid/liquid extraction
was made with n-hexane 3 times.
The lipid extract was concentrated and separated by
column chromatography on neutral alumina/silica (v:v)
(5% deactivated). Aliphatic hyrocarbons (F1) were
eluted with 20 ml n-hexane and polycyclic aromatic hy-
drocarbons (F2) with 20 ml (9:1, v/v) then 30 ml (7:3,
v/v) hexane/dichloromethane. Both fractions were con-
centrated under vacuum evaporation to dryness and then
redissolved in 50 µl of n-hexane prior to the analysis by
gas chromatography.
2.3. GC/FID and GC/MS
The quantitative analysis of hydrocarbons was carried
out using a HP6890 Agilent chromatograph equipped
with a flame ionization detector. F1 fraction was injected
on a fused silica capillary column DB-5MS (J&W, 30 m,
0.25 µm), using Helium as carrier gas. The oven tem-
perature program used was: 60˚C, raised to 100°C at a
rate of 25°C/min, and to 310°C at 2°C/min, with an iso-
therm of 70 min at 310°C.
Hydrocarbons were identified by comparison of reten-
tion times with known standards. of n-alkanes, ranging
from n-C15 to n-C32. To confirm the structure of hydro-
carbon compounds, selected samples were also analysed
by gas chromatography-mass spectrometry. The GC/MS
analysis was carried out on a HP6890 GC coupled to a
HP5973 Mass Selective Detector, equipped with a DB-
5MS fused-silica column (J&W, 30 m, 0.25 mm i.d.,
0.25 µm film thickness). Helium was used as carrier gas.
The oven temperature program employed was the same
as in GC/ FID.
3. Results and Discussion
3.1. Fraction 1
This fraction corresponds to non aromatic hydrocarbons
(NAH). They are composed of normal and isoprenoid
alkanes, alkenes, hopanoids and an envelope of unre-
solved complex mixture (UCM). They were present in all
samples. The total NAH concentrations range from 24.1
to 2731 µg/g dry weight (dw) (Table 1), being maxi-
mized at S4 station, which is located off the mouth of
Martil river. This latter is well known for being a major
source of pollution in the area.
The comparison of our results with those obtained for
bivalve organisms in other studies proves to be difficult
for two major reasons: first, the species used in almost all
studies dealing with hydrocarbon contamination are not
the same and second, NAH concentrations have not been
reported in any of these studies. Concentrations generally
reported are the sum of total n-alkanes. This can facili-
tate the comparison; nevertheless it can also underesti-
mate the bulk amounts of NAH.
3.1.1. n-Alkanes
Concentrations of total n-alkanes vary between 2.2 and
68.2 µg/g dw (Table 1), with few exceptions recorded
for some sites such as S4 station (A: 169.8 µg/g and D:
97.4 µg/g) and S3 station (C: 243 µg/g). In comparison
with other studies dealing with NAH contamination in
bivalve organisms, these results remain within the range
reported for areas considered as mildly polluted [16].
Concentrations for all seasons except summer are higher
than those reported for mussels in Guanabara Bay [17],
Southeast Florida [18], Galicia [7,16], southern Baltic
sea [19] and Gulf of Naples [6] (Table 2). The levels in
summer fall in the same range as those reported for Bay
of Todos os Santos (Brazil) [20]. However, the total
n-alkane concentration recorded in S4 and S3 are very
high but similar to those found by Soler and al., [21] for
mussels in Galicia (Table 2).
The results obtained show a general distribution of n-
alkanes ranged between n-C15 and n-C30; compounds
lighter than n-C15 could be lost during the evaporation of
extraction solvent. This distribution appears bimodal for
most samples (Figure 2). The first mode, consisting in
short chain n-alkanes, is predominant and constitutes
more than 50% of total n-alkanes (% C < 25 vary from
22 to 100%) (Table 1). Bimodal n-alkane distribution
has also been reported in oysters [22], winkles [23] and
limpets [24] and has been proposed as originated from
mixed contributions of terrestrial plant waxes and petro-
leum sources [25].
The dominant peaks are mainly n-C17, n-C27, n-C29 and
n-C31 in most samples. This feature is related to plank-
tonic [26-28] and terrestrial plant wax sources [29].
Nevertheless, some samples show higher abundance of
n-C18 and n-C19 over n-C17, which is often attributed to
bacterial sources [28]. The biogenic source is also con-
firmed by the presence of n-alkenes, identified in the
range of C16 to C21. C15 to C19 n-alkenes are related to
Copyright © 2011 SciRes. IJG
Table 1. Non aromatic hydrocarbon (NAH) levels (µg/g dry weight) in cockle samples from stations along the northwestern
Moroccan Mediterranean coast collected in different seasons (spring (A), summer (B), autumn (C) and winter (D)). .
NAH UCM U/R %UCM Tot n-alk %C < 25Pr/Ph n-C17/Pr n-C18/PhCPI
S1-A 40.8 23.4 1.34 57.18 34.19 70.3 0.57 3.28 0.86 1.59
S3-A 42.5 31.6 2.91 74.44 1.84 81.1 0.63 3.89 1.64 1.01
S4-A nd nd nd nd 169.8 72.8 0.72 3.74 2.95 0.5
S5-A 38.9 18.6 0.92 47.91 83.56 69.3 -- 0.85 -- 0.97
S6-A 453.7 380.4 5.19 83.84 16.09 97.3 0.44 1.26 0.56 1.19
S7-A 24.1 12.0 0.99 49.87 1.89 82.6 0.73 1.15 0.65 1.36
S1-B 40.9 32.16 3.68 78.62 1.77 77.6 1.25 2.91 1.07 1.64
S2-B 45.5 32.45 2.48 71.28 3.19 83.8 0.81 3.21 1.15 1.4
S3-B 38.0 17.5 0.85 46.04 3.28 59.8 0.73 7.47 1.28 1.97
S4-B 43.5 -- -- -- 2.31 85.8 0.23 2.20 2.84 0.84
S5-B 56.3 37.46 0.98 66.52 5.12 68.7 0.45 4.08 1.92 1.27
S6-B 78.7 50.33 1.78 63.99 7.63 84.2 0.38 4.37 2.34 0.86
S7-B 43.5 26.77 1.6 61.56 3.77 67.9 0.44 3.11 1.17 1.11
S1-C 191.0 -- -- -- 3.31 22.63 1.05 1.88 1.37 1.92
S2-C 122.04 10.83 0.10 8.87 1.26 32.61 0.79 1.39 0.87 1.58
S3-C nd nd nd nd 243 95 0.6 2.9 1.10 1
S4-C 255.35 243.05 19.77 95.19 3.66 22.51 0.76 0.08 0.51 2.05
S5-C 153.27 140.72 11.21 91.81 3.02 53.32 0.56 4.47 1.69 1.91
S6-C 179.77 24.36 0.16 13.55 1.63 41.77 0.15 0.76 0.91 1.69
S7-C 135.75 21.78 0.19 16.04 2.09 65.90 0.38 4.58 1.99 1.48
S3-D 81.99 33.85 0.70 41.28 2.17 98.02 0.69 4.17 1.57 1.08
S4-D 2731.89 2227.51 4.42 81.54 97.41 100 0.53 2.06 1.00 0,94
S5-D 391.13 241.10 12.81 92.76 2.69 87.19 0.53 2.15 1.42 0.73
S6-D 180.72 85.41 0.28 21.84 3.48 89.75 0.53 1.95 1.40 0.94
S7-D 259.92 36.43 0.25 20.16 2.16 70.59 0.44 3.27 1.57 1.06
algal sources [30] and are phytoplankton biomarkers (e.g.
[28,30-33]). The squalene, a biogenic compound [28,34]
is also identified in most samples.
On the other hand, the profiles of n-alkanes show a
homogenous distribution between odd and even number
of carbons without any predominance. This fact was
confirmed by the CPI (Carbon Preference Index) values
close to unity (0.5 - 2.05) (Table 1). This could indicate
an oil contamination [15,29,35]. However, microbial
contributions of long chain n-alkanes or microbial altera-
tion of terrestrial n- alkanes [34-36] cannot be excluded.
3.1.2. UCM
In addition to the chromatographically resolved com-
pounds, an unresolved complex mixture (UCM) of hy-
drocarbons is present in most samples (Figure 3), in the
range n-C25 to n-C35. However, in some samples, it ap-
pears as a bimodal hump in the range n-C17 to n-C25 and
n-C29 to n-C35. The UCM is generally considered as a
mixture of many structurally complex isomers and ho-
mologs of branched and cyclic hydrocarbons that cannot
be resolved by capillary columns [36,37]. Further, the
presence of the UCM in the aliphatic fraction is consid-
ered as the most important indicator of petrogenic pollu-
tion by weathered or degraded petroleum residues [36]
when the maximum height occurs mainly in the higher
molecular weight. Yet, it has also been linked to bacterial
degradation of natural organic inputs (algal detritus)
[36,37]. The UCM concentrations vary from 10 to 2227
µg/g dry weight (Table 1). The ratio of the unresolved to
resolved components (U/R) has been calculated for most
samples. Usually U/R > 4 is used as a criterion for the
presence of important petroleum residues [38]. In this
study, 5 samples show U/R > 4, (S4: C, D; S5: C, D; S6:
A). These results can be explained by the nearness to
continental discharges.
Copyright © 2011 SciRes. IJG
Table 2. Aliphatic hydrocarbon levels (µg/g dry weight) in organism samples from the Mediterranean coast and other coasts
in the world.
Sites Organism Sampling Total aliph/alk UCM NAH Reference
Galicia (Spain)
Mussels (Mytilus
galloprovincialis) Cockles
(Cerastoderma edule)
89.46 - 5098.01 ng/g
317.49 - 17,579.37 ng/g
Not reported Not reported Carro et al., 2006
Guanabara bay
(Brazil) Mussels (Perna perna) 1996
Winter: 520 - 1461 ng/g
Summer: 309 - 829 ng/g
Not reported Not reported Azevedo et al.,
Gulf of Naples
Mussels (Mytilus
Fish (Boops boops,
Scorpaena scrofa,
Trachinus araneus, Gobius
paganellus, Coris julis,
Merluccius, Boops salpa)
771 - 33,202 ng/g
630 - 48,200 ng/g
(C18,C20,C22,C24,C26 ,C28,C30,C32 ,C36)
Not reported Not reported Amodio-Cocchieri
et al., 2003
Florida Bivalves (Peria Columbus) 1990-1992 Mean value +/– 1; sd: 3156 +/– 1212
(C12-C30) Not reported Not reported Snedaker et al.,
Galicia (Spain) Mussels (Mytilus
galloprovincialis) 1990-1991
Free-population: 0 - 6196 ng/g
Raft-farmed population: 613 - 4690 ng/g
(C18,C19,C20,C22,C24 ,C28,C32,C36 )
Not reported Not reported Hermida et al.,
Galicia (Spain) Mussels (Mytilus
galloprovincialis) 1990-1991
Natural population Mean value (sd):
1430(717) - 2038(677) ng/g
Raft-farmed population Mean value (sd):
1133(110) - 1845(867)
(C18,C19,C20,C22,C24 ,C28,C32,C36 )
Not reported Not reported Hermida et al.,
Galicia (Spain) Mussels (Mytilus
reported 4.6 - 220 µg/g (Resolved hydrocarbons)46 - 760 µg/g Not reported Soler et al., 1989
Bay of Todos os
Santos (Brazil)
Mussels (Mytilus sp.)
Oysters (Crassostrea sp.) 1985-1986
3.2 µg/g
2.4 µg/g
5.8 µg/g Not reported Tavares et al.,
Southern Baltica
Sea Mussels (Mytilus edulis) 1981 250 - 7900 ng/g
(C13-C30, Prystane, Phytane) Not reported Not reported Law and
Andrulewicz, 1983
NW Moroccan
coast Cockles (Acanthocardia
Tuberculata) 2003
Spring: 1.7 - 169.8 µg/g(C17-C28)
Summer: 1.6 - 7.6µg/g (C16-C30)
Autumn: 1 - 236 µg/g (C17-C34)
Winter: 1.5 - 96.2 µg/g (C17-C25)
10 - 2227 µg/g 24 - 2731 µg/g This study
3.1.3. Isoprenoids
Pristane (Pr) and phytane (Ph) are the most common iso-
prenoids detected in marine organisms, sediments and
waters [24]. They are present in most of our samples.
The ratio of pristane vs. phytane (Pr/Ph) has been used as
an indicator of the redox conditions in sediments and/or
as an indicator of oil slicks [24,39]. In uncontaminated
sediment the Pr/Ph ratio is higher than one (usually be-
tween 3 and 5) [40]. The ratio Pr/Ph in all our samples is
lower than 1 confirming a petrogenic contamination.
On the other hand, the ratios n-C17/Pr and n-C18/Ph,
usually used as indicators of hydrocarbon degradation
[41], indicate, for most samples, degraded material of
biogenic inputs. However, most samples show high val-
ues of n-C17/Pr ratio which could be related to the rela-
tively high contents of n-C17 in several stations.
3.1.4. Hopanes
Hopanes are ubiquitous compounds in crude oils, and
resistant to weathering processes and bacterial degrada-
tion [36]. Their composition is usually characteristic of
pollution sources; therefore they have been used as an
identifier of petroleum pollution [42,43]. In this study,
hopane series have been identified in all samples by mo-
nitoring m/z 191 in GC/MS analysis. The identified
compounds have the thermodynamically stable 17α(H),
21β(H) configuration. Such isomeric configuration occurs
in crude oil and mature rocks [42]. The hopane distribu-
tion is characterized by the presence of C30 with subordi-
nate amounts of 18α(H)-22,29,30-trisnorneohopane (Ts),
17α(H)-22,29,30-trisnorhopane (Tm), 17α(H),21β(H) 29-
norhopane and the extended C31-C35 α-hopanes series.
Copyright © 2011 SciRes. IJG
Figure 2. n-Alkane distribution from C15 to C35 of cockle samples collected from KSr station during the 4 seasons corre-
sponding to S7-A, S7-B, S7-C, and S7-D.
Figure 3. Chromatogram of Non Aromatic Hydrocarbons obtained by GC/FID for cockle samples in stations S3 (spring) and
S6 (summer).
These latter occur as 22S and 22R epimers, characteris-
tics of oil derived hydrocarbons [44], which confirms a
fossil origin as already suggested by the CPI values, the
presence of UCM and the Pr/Ph ratio (Figure 4).
3.2. Fraction 2
Inversely to what expected, polycyclic aromatic hydro-
carbons (PAH) are present in very low concentrations,
below the limit of GC detection in all organism samples.
However, the analysis showed the presence of com-
pounds known as Long Chain Alkylbenzenes (LAB).
These compounds were reported, for the first time, by
Grimalt et al., [45] in sediments from the Catalane coast.
3.2.1. Long Ch ain Al kylbenzenes (LAB s)
Long chain alkylbenzenes are important intermediates in
the manufacture of the detergent surfactants [46]. They
are the raw material for the industrial production of the
linear alkylbenzenesulfonates (LAS) [43,47,48], which
are the anionic surfactants commonly used in domestic
synthetic detergents [43,47].
1% to 3% of LABs are unsulfonated during the syn-
thesis of LAS-detergents [43,47,48], and can be carried
into the aquatic environment in association with domestic
wastes [43,47-50]. Since LABs are more resistant to mi-
crobial attack in the environment than LAS [47,48,51,52],
they have been widely utilized for monitoring sewage
inputs [48,51]. They have been detected in river waters
[48,53], marine sediments [52,54] and marine organisms
In this study, linear alkylbenzenes containing alkyl
chains ranging from 13 to 14 carbon atoms were detected
in most samples analyzed by monitoring m/z 91 and m/z
105 in the GC/MS analysis (Figure 5). Total concentra-
tions of LABs vary from 478 to 1954 ng/g dw (Table 3).
The absence of the lighter homologs could be related to
the selective metabolism by the organism as observed in
fishes [56]. It can also be related to the mode of nutrition
of cockles. These organisms are known to have an active
suspension feeding mode; they feed on the particulate
phase. Indeed, it has been demonstrated that this phase
Copyright © 2011 SciRes. IJG
Figure 4. Characteristic GC/MS mass fragmentogram for m/z 191. Ts: 18α(H)-22,29,30-trinorneohopane; Tm: 17α
(H)-22,29,30-trinorhopane, C29: 17α(H), 21β(H) 29-norhopane, Hopanes; (C31-C35): hopane series with 22S and 22R epi-
Table 3. Linear alkylbenzenes concentrations (ng/g dw) in
cockles from sampling sites of North-Western Moroccan
Mediterranean coasts.
S1 S3 S4 S5 S6 S7
13-LAB 6 20.92 44.39 17.91 32.79 22.2226.04
13-LAB 5 24.67 17.39 23.01 33.18 16.5312.42
13-LAB 4 0.89 24.11 31.90 48.33 26.9220.09
13-LAB 3 35.57 65.19 67.65 139.79 72.6362.00
13-LAB 2 346.04 463.33 523.46 1081.44 501.67510.11
14-LAB 6 579.37 16.61 29.56 66.46 26.7416.62
14-LAB 5 17.46 14.77 36.39 69.86 168.4621.09
14-LAB 4 31.56 35.31 38.55 64.88 36.4937.88
14-LAB 3 20.72 37.26 57.66 142.74 71.9330.08
14-LAB 2 103.57 92.32 113.62 285.48 134.19125.95
LAB 1166.80 788.47 935.31 1954.42 1076.50847.66
concentrates the higher homologs of LABs [57].
4. Seasonal and Spatial Variations
This monitoring study points out the important amounts
of hydrocarbons accumulated in bivalve organism’s tis-
sues. The concentrations of non aromatic hydrocarbons
vary from 24.1 to 2731.89 µg/g. Maximum values were
observed in S4 and S6 sites corresponding to stations
located near the mouths of Marltil and Oued Laou rivers,
respectively. Moreover, site S2, located near the pleas-
ance harbor of Kabila, shows sometimes high values of
NAH. On the other hand, minimum values were found at
stations located far from any sources of pollution.
The distribution of NAH shows both seasonal and spa-
tial variations. The spatial variation was also revealed by
the results of the MYTILOS project, which underlines
the urban and industrial poles and the mouths of the main
streams as the most polluted sectors, with a distinct dilu-
tion effect noted for the organic compounds [58].
Indeed, the coastal fringe from F’nideq (S1) to Kaâ
Srass (S7) receives pollutant inputs from various point
Copyright © 2011 SciRes. IJG
Figure 5. Characteristic GC/MS mass fragmentogram for m/z 91 showing the distribution of linear alkylbenzenes (13 and 14
indicate the alkyl chain length, and n refers to the position of the phenyl group on the alkyl chain).
sources. The spatial variation is strongly influenced by
the proximity to the sources, marine ones as harbors and
shipping activities, and continental ones as urban dis-
missals. The latter is strongly marked by the presence of
LABs compounds. In fact, this zone receives an impor-
tant amount of mineral and organic pollutants emanating
from coastal agglomerations. Therefore, Martil and Oued
Laou rivers mouths would be the most exposed sites to
anthropogenic effluents. However, LABs are also present
in sites far enough from the zone of pollution emissions
(e.g., station S6). This can be attributed to the transport
of pollutants by currents, and to the resistance of
hydrocarbon pollutants.
Our results also reveal significant seasonal variations.
Concentrations in winter and autumn are much higher
than those in warm seasons, with maximum values re-
corded in winter. This is likely due to the higher river
flow in humid seasons (winter and autumn) when rivers
expel important discharges and associated pollutants
seawards. In dry seasons highest concentrations are re-
corded in stations close to marine sources, such as har-
bors (Kabila site) and shipping activities.
Seasonal and spatial distributions of NAH, illustrated
in Figure 6, show that the accumulation of NAH is
strongly controlled by the proximity to marine pollution
sources as well as to land-based ones. The latter are con-
firmed by the presence of the long chain alkylbenzenes
reflecting domestic wastewater inputs.
5. Conclusions
This investigation provided important information on the
contamination of western Mediterranean coasts of Mo-
rocco by hydrocarbons. Concentrations of total non aro-
matic hydrocarbons are important but still not alarming.
In comparison with other sites, our results fall within the
Figure 6. Seasonal and spatial distribution of total non
aromatic hydrocarbon concentration in the study area
(Fnideq-Kaâ Srass) (spring (A), summer (B), autumn (C)
and winter (D).
range reported for areas considered to be mildly polluted.
The qualitative and quantitative analysis points out two
major sources of hydrocarbons: natural sources linked to
phytoplankton, bacteria and continental plants and anth-
ropogenic sources related to petrogenic inputs from
shipping activities and harbors as well as to urban wastes
from nearby agglomerations transported by rivers. The
distinct anthropogenic sources strongly control the sea-
sonal and spatial variations observed.
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