Vol.3, No.9, 775-782 (2011) Natural Science
http://dx.doi.org/10.4236/ns.2011.39102
Heavy metals pollution in sediment cores from the Gulf
of Aqaba, Red Sea
Tariq Al-Najjar1*, Mohamad Rasheed2, Zaid Ababneh3, Anas Ababneh3, Hosam Al-Omarey3
1Faculty of Marine Sciences, Department of Marine Biology, Jordan University, Aqaba Branch, Aqaba, Jordan;
*Correspondence Author:
2Marine Science Station, Aqaba, Jordan;
3Physics Department, Yarmouk University, Irbid, Jordan.
Received 9 August 2011; revised 11 September 2011; accepted 25 September 2011.
ABSTRACT
The distribution of metals (Cd, Cr, Pb, Cu, Ni and
Zn) was determined in sediment cores collected
from five major areas representing different an-
thropogenic activities along the Jordanian coast
during 27 February-11 March 2008. Metal con-
centrations in these sediments were relatively
low compared to reported values from polluted
areas. At some of the sites metal concentrations
showed fluctuations with depth in the core
suggesting changes in metal loading with time.
The calculated contamination factors (CFs) for
the suite of metals decreased in the following
order Cd > Pb > Cr > Ni > Zn > Cu. The Pollution
Loading Index (PLI) calculated for the different
areas were highest at Phosphate Loading Berth
(0.008, 0.2607, 0.0161, 0.007, 47.9375 and 0.0296
for Cu, Pb, Ni, Zn, Cd and Cr, respectively) and
lowest at Hotel Area (0.0001, 0.0075, 0.0008,
0.0006, 1.0483 and 0.0005 for Cu, Pb, Ni, Zn, Cd
and Cr, respectively) with others sites between
these extremes. Result of this study could be
used to assess the magnitude of pollution at
each site and guide rational management deci-
sions. Moreover, the data constitutes a baseline
against which future anthropogenic effects can
be assessed.
Keywords: Metals; Core sediments; Pollution
Loading Index; Contamination Factor; Gulf of Aqaba;
Red Sea
1. INTRODUCTION
Within rapid industrialization and economic develop-
ment in coastal areas around the world heavy metals are
introduced to the coastal environment [1,2]. Studies have
been curried to evaluate heavy metal distribution in sur-
face sediments to assess the degree of pollution in the
marine environment [3,4]. Heavy metals are transported
as either dissolve species in water or in association with
suspended sediments and are subsequently deposited and
stored in bottom sediments. After burial some the distri-
bution of some redox sensitive metal could be modified
by natural processes in the sediment. The bioaccumula-
tion of heavy metals in coastal sediments can be hazar-
dous to the local population which uses the coast area for
fishing and recreation activities [5,6]. Metal abundance
in sediments cores can provide a historical record of
changes in metal contamination over time and their rela-
tion to historical changes in land use and anthropogenic
activity [7,8]. Specifically, if the sediment core is intact
and sediments remain undisturbed by human activities or
extensive bioturbation then a continuous record over
time could be obtained [6,9]. Most of the previous stu-
dies, dealing with levels of heavy metal pollution in the
coastal areas along the Jordanian coast focused on relat-
ing heavy metals in surface sediments to those seen in
living organisms such as algae and seagrass [10], sea
urchin [11] and sea cucumber [12]. The objective of this
work is to study the concentration of six metals nickel
(Ni), copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd)
and chromium (Cr) in sediment cores collected at 3 water
depths (5, 15 and 35 m) at five sites characterized by
various industrial and tourism activities along the Jorda-
nian coast of the Gulf of Aqaba. These data will provide
a historical record of spatial and temporal changes in
metal pollution. To quantify the magnitude of pollution
two measures were employed: Contamination Factor (CF)
and Pollution Load Index (PLI).
2. METHODS
2.1. Study Area
The Gulf of Aqaba is the north eastern segment of the
Red Sea. It is located between 28˚ - 29˚30'N and 34˚30' -

T. Al-Najjar et al. / Natural Science 3 (2011) 775-782 776
35˚E [13] (Figure 1). The Gulf is deep (max. depth 1800
m) and narrow (180 km long, 14 - 26 km wide) and is
surrounded by desert mountains with negligible inputs of
fresh water or run-off. This area has a hot and dry
climate with average temperature of 23˚C. The sea sur-
face temperature ranges between 21˚C during winter and
27˚C during summer with temperatures of 21˚C even in
deep waters. The net evaporation in this area is 0.5 - 1
cm·day–1 [13]. The study area lies within the Jordanian
portion of the Gulf of Aqaba, located at the most nor-
thern and northeastern side of the Gulf and extended
about 27 km [14]. The coastal areas on the Gulf are im-
portant environmental, economical, and recreational
areas in Jordan.
2.2. Sample Collection and Treatment
Sediments were collected by scuba diving at five
coastal locations along the Jordanian coast (Hotels Area
(HA), Phosphate Loading Berth (PLB), Marine Science
Station (MSS), Tala Bay (TB) and Industrial Area (IA))
(Figure 1). Cores were all obtained within a short time
interval between the 27th of February and 11th of March
2008. The selected locations represent the different types
and extend of anthropogenic activities occurring along
the Jordanian coast. Specifically the Hotels Area lies on
the beach of city of Aqaba and is impacted by a high
density of visitors; the Phosphate Loading Berth (PLB) is
situated about 3 km south of Aqaba city and it is the port
used for loading and export of phosphate from Jordan;
the Marine Science Station (MSS) is located 10 km south
of Aqaba city close to the passengers port where ferry
traffic arrives from Egypt, the MSS sites is known for its
wide variety benthic habitants and excellent back reef
lagoon; Tala Bay Marina (TB) lies about 14 km south of
the city of Aqaba, it is an integrated residential and
tourist resort; the Industrial Area (IA) site is located 15
km south of the main port of Aqaba, at this location
several plants for fertilizer and phosphate ore production
and handling as well as storage and loading facilities.
Sediment cores were collected at three different water
column depths (5 m, 15 m and 35 m) at each location
using a sharp stainless steel core of 8 cm in diameter.
Each core was about 15 cm long and was sectioned in the
laboratory into three sections (0 - 5 cm, 5 - 10 cm and 10
- 15 cm). Sediment samples were dried until a constant
weight was obtained, after that samples were homoge-
nized and kept in Naylon bags. A subsample (100 g) was
used for grain size analysis using standard dry sieving
and sedimentation techniques [15].
2.3. Heavy Metal Analysis
For heavy metal analysis 0.2 g of the homogenized
sediment was dried at 105˚C, placed in pre-cleaned 100
ml glass beakers, and 8 ml of 69.5% ultra-pure nitric acid
was added to each beaker. Samples were left to react at
room temperature for 4 hrs. Beakers were then put on a
hot plate at 100˚C for 6 hrs, allowed to cool to room
temperature and heated again to near dryness in order to
remove the nitric acid. The residue was dissolved in 8ml
of 1% nitric acid and kept on a hot plate for about 1 hr to
34.8 34.85 34.9 34.953535.05
Longitude (E)
29.35
29.4
29.45
29.5
29.55
Latitude (N)
Marine Science Station
G U L F O F A Q A B A
0 1 2 3 4 5 km
34 34.5 35 35.5
27
28
29
Red Sea
Gulf of Aqaba
Hotels Area
Phosphate Port
Tala Bay
Industrial Area
Figure 1. Sampling sites at the northern Gulf of Aqaba, Red Sea.

T. Al-Najjar et al. / Natural Science 3 (2011) 775-782 777
enhance dissolution. The samples were allowed to cool
to room temperature and then filtered on a Whatman
filter paper number 43. Samples were finally diluted to
25 ml with 1% nitric acid. Concentrations of Cd, Cr, Ni,
Pb, Cu and Zn were measured on a Jena AA 400 atomic
absorption spectrophotometer by direct aspiration into
air-acetylene flame. The instrument was programmed to
report the mean value and standard deviations of three
repeat analyses of each sample. The precision of the
whole procedure was assessed by 10 replicates for a
sample and the results agreed to within 3%. Duplicate
blanks were prepared and analyzed with each batch of
digested samples. The mean value of the blank was
subtracted from the readings of the sample to give the
final reading. Three standard solutions that expected
range of the element concentrations in the samples were
also prepared and analyzed along with the samples. The
standard calibration curves were linear. The final element
concentrations are reported in µg·g–1 unit.
3. RESULTS AND DISCUSSION
3.1. Sediment Type
The texture and chemical properties of the sediment at
the different sites were quite different. Sediments from
the northernmost locations were fine, black and oxygen
deficient, whereas sediments from the southern locations
were white, better oxygenated, and slightly coarser [16].
Table 1 shows the sediment type at the various sampling
locations. The sediment texture is sandy at MSS, TB and
IA indicating of the high energetic regime of alongshore
currents allowing the washout the finer particles [6,17];
the hotel area has sandy silt sediments and the sediments
are PLB are dominated by clays. The fine sediments at
PBL are a result of substantial amounts of phosphate
powder deposited at the site from dust ore blowing dur-
ing the process of shipment. This site also has a higher
sedimentation rate compared to the other sites along the
Jordan coast [16].
3.2. Trends in Element Concentrations in
the Sediment Cores
The heavy metals concentration profiles obtained from
the collected cores are shown in Figure 2. Different
elements exhibited different trends in their vertical dis-
tribution at the different sites.
For Chromium (Cr), at most sites the highest detected
concentrations were recorded in the interval between 10 -
15 cm. However, PLB Cr profiles showed an additional
peak at 5 - 10 cm. Analytical results obtained by [18,19]
indicated that Cr as (Cr6+) is relatively mobile and mig-
rate to the reduced zone which is typically present at the
deeper levels in our cores. Indeed this may explain the
presence of a Cr peak at the deepest interval where oxy-
gen is most depleted and the presence of a peak at shallo-
wer depth at PLB where sedimentation rates are highest
and thus oxygen penetration is retarded. Nickel (Ni),
which is quite abundant in the Earth’s crust, enters sur-
face waters from the dissolution of rocks and soil, from
biological sources, atmospheric fallout, and especially
Table 1. Depth, date, location color, type and organic matter content in sediments at each of the sampling sites.
Site Depth (m) Date Latitude Longitude Color Type
MS 5 7 Mar 2008 29˚27'555''N 34˚58'435''E Brown to Gray Sandy
MS 15 4 Mar 2008 29˚27'555''N 34˚58'435''E Brown to Gray Sandy
MS 35 7 Mar 2008 29˚27'555''N 34˚58'435''E Brown to Gray Sandy
HA 5 27 Feb 2008 29˚27'986''N 34˚59'532''E Black Sandy Silt
HA 15 4 Mar 2008 29˚27'986''N 34˚59'532''E Black Sandy Silt
HA 35 4 Mar 2008 29˚27'986''N 34˚59'532''E Black Sandy Silt
IA 5 12 Mar 2008 29˚22'705''N 34˚57'602''E White Sandy
IA 15 12 Mar 2008 29˚22'705''N 34˚57'602''E White Sandy
IA 35 12 Mar 2008 29˚22'705''N 34˚57'602''E White Sandy
PL 5 10 Mar 2008 29˚30'191''N 34˚59'465''E Gray to Black Clay
PL 15 10 Mar 2008 29˚30'191''N 34˚59'465''E Gray to Black Clay
PL 35 10 Mar 2008 29˚30'191''N 34˚59'465''E Gray to Black Clay
TB 5 11 Mar 2008 29˚26'386''N 34˚58'148''E Brown to Gray Sandy
TB 15 11 Mar 2008 29˚26'386''N 34˚58'148''E Brown to Gray Sandy
TB 35 11 Mar 2008 29˚26'386''N 34˚58'148''E Brown to Gray Sandy

T. Al-Najjar et al. / Natural Science 3 (2011) 775-782 778
0.00
0.01
0.01
0.02
0.02
0.03
0.03
0.04
0.04
MSS1
MSS2
MSS3
HA1 HA2 HA3
IA1 IA2 IA3
PLB1 PLB2 PLB3
TB1 TB2 TB3
interval sites
concentration (µg.g)
Cu
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
MSS1
MSS2
MSS3
HA1
HA2
HA3
IA1
IA2
IA3
PLB1 PLB2 PLB3
TB1 TB2 TB3
interval sites
concentration (µg.g)
Pb
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
MSS1
MSS2
MSS3
HA1 HA2 HA 3
IA1
IA2
IA3
PLB1 PLB2 PLB3
TB1 TB2 TB3
interval sites
concentration (µg.g)
Zn
0.00
0.20
0.40
0.60
0.80
1.00
1.20
MSS1
MSS2
MSS3
HA1 HA2 HA3
IA1 IA2 IA3
PLB1
PLB2
PLB3
TB1
TB2
TB3
interval sites
concentration (µg.g)
Cr

T. Al-Najjar et al. / Natural Science 3 (2011) 775-782 779
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
MSS1
MSS2
MSS3
HA1
HA2
HA3
IA1 IA2 IA3
PLB1
PLB2
PLB3
TB1
TB2
TB3
interval sites
concentration (µg.g)
Ni
0.000
1.000
2.000
3.000
4.000
5.000
6.000
MSS1
MSS2
MSS3
HA1
HA2
HA3
IA1
IA2
IA3
PLB1
PLB2
PLB3
TB1
TB2
TB3
interval sites
concentration (µg.g)
Cd
0.000
0.200
0.400
0.600
0.800
1.000
1.200
MSS1
MSS2
MSS3
HA 1
HA 2
HA 3
IA1
IA2
IA3
PLB1
PLB2
PLB3
TB1
TB2
TB3
interval sites
concentration (µg.g)
Cr
Figure 2. Mean metal concentration (µg·g–1) at all sampling site.
from industrial processes and waste disposal [20]. The
vertical distribution of Ni exhibited a distinct in- crease
in concentrations in the 10 - 15 cm section at both PLB
and IA and similar profiles with somewhat lower
concentrations at other sites. According to [21], the in-
crease of Ni content at subsurface layers is due to Ni sor-
ption onto manganese oxyhydroxides. It is well known
that Ni is insoluble at the pH values of marine en- viron-
ment (>6.7) and exist predominantly as Ni hydroxides
[22] which is turn are quickly incorporated into particles.
Copper (Cu), is one of the most common contaminants
associated with urban runoff. Important anthropogenic
inputs of Cu in estuarine and coastal waters include sewage
sludge dump sites, municipal waste discharge, and anti-
fouling paints [23]. In relatively clean sediments, Cu
concentrations are about 50 µg·g–1 while sediments with
concentration of >60 µg·g–1 are classified by the EPA as
contaminated [24]. According to the cal- culated overall
average concentration of Cu (0.03 µg·g–1) in the five
studied sites the sediments studied are uncontaminated
with respect to Cu. The vertical profiles of Cu in the
studied cores showed similar patterns of distribution at

T. Al-Najjar et al. / Natural Science 3 (2011) 775-782 780
all sites. At PLB slightly higher concentration at 5 - 15
cm (0.034 µg·g–1) was recorded but the difference be-
tween this concentration and those recorded at other sites
is not statistically significant. Zinc (Zn) is a naturally
abundant element present as a common contaminant in
agricultural food wastes, manufacturing of pesticides as
well as in antifouling paints. The vertical distribution
pattern of Zn was similar to that of Cr. Down core
profiles of Zn suggest no changes in Zn pollution over
time in this region as also recognized by [25]. However,
at PLB a maximum in Zn was found in the 5 - 10 cm
interval (0.42 µg·g–1) with lower values above and below.
This finding might be attributed to the upward migration
of Zn during organic matter degradation [25] or possibly
to a period with higher Zn pollution at this site.
Cadmium (Cd) which is a transition element behaves in
the environment as a cumulative toxin [24]. It is listed by
EPA as one of 129 priority pollutants and among the 25
most hazardous substances. Moreover, there is an inter-
national agreement forbidding discharge of any Cd into
the sea [26]. It has been suggested that natural sources of
Cd contribute 10% - 30% through windblown transport
of soil particles and volcanic emissions [23]. The main
source of Cd to the marine environment is mainly
anthropogenic through atmospheric loading of refining
and use of Cd [23]. The vertical distribution pattern of
Cd in our cores showed an increase of its content with
increasing depth in the core. Higher Cd contents in the
PLB core (4.79 - 5.23 µg·g–1) compared to the con-
centrations at other sites of this study (0.098 - 0.187
µg·g–1) is consistent with the higher metal contamination
at this site. It is well recognized that Cd is sensitive to
redox changes; it is soluble in oxygenated conditions and
precipitates immediately where reducing conditions are
encountered [27]. Lead (Pb) compounds are also poten-
tially harmful, especially tetraethyl lead [28]. It is listed
by EPA as a carcinogen material. Concentrations of Pb in
the studied sediments like Cd and Zn show low concen-
trations (0.1 - 0.123 µg·g–1) with slightly higher values
of Pb in PLB core, The maximum value of (4.07 µg·g–1)
was obtained in the 5 - 10 cm, interval and the minimum
value was in the 0 - 5 cm section. High Pb concentrations
are attributed to several sources such as boat exhausted
systems, spillage of oil and other petroleum compounds
form mechanized boats employed for fishing [29,30], all
of these sources are present in the study area. In addition
to these sources, atmospheric input of Pb generated from
automobile exhaust emission can contribute a significant
amount of Pb at PLB area which is located at the main
port area where intensive traffic activities exists.
3.3. Estimating Pollution Impacts
A number of methods have been put forward for quan-
tifying the degree of metal enrichment in sediments. Va-
rious authors [2,6,31,32] have proposed pollution impact
scales or ranges to convert the numerical concentration
results into broad groups of pollution ranges (e.g. low to
high intensity). A contamination factor [33] is defined as
the metal concentration in sediment divided by some
background base value for each element. The back-
ground value corresponds to the baseline concentrations
reported by [34] and is based on element abundances in
sedimentary rocks (shale) (Table 2). The ranges used to
describe the contamination factor are: CF < 1 is consi-
dered as low contaminated; 1 < CF < 3 is moderate con-
tamination; 3 < CF < 6 is considerable contamination
and CF > 6 is high contaminations.
The CF values for the various metals are shown in
Table 3. The metal CF levels at all sample sites are pre-
sent in the following order Cd > Pb > Cr > Ni > Zn > Cu.
Cadmium concentration are relatively high in the study
area, the CF ranged between 1 - 1.8 suggesting low to
moderate contamination in all stations except at PLB
where the CF value indicates extreme contamination (CF
= 48). Low contamination factor was observed for Pb, Cr,
Ni, Zn and Cu at all stations.
We also computed the pollution loading index (PLI)
for our samples according to [33] using the following
equation:

1
123 n n
PLICF CFCFCF




where: PLI = pollution loading index; CF = contami-
nation factor; n = number of metals investigated.
The PLI was calculated for the five areas under in-
vestigation using the six investigated metals (Cd, Pb, Ni,
Cu, Zn and Cr). It was observed that the highest PLI was
found at PLB (0.06), while the lowest was calculated for
Tala Bay (0.001), the calculated PLI were found in the
following sequences: PLB > HA > IA > MSS > TB. The
PLI values computed in our study are much lower than
those reported [6], for the Red Sea (7.5 - 5.6; Table 4)
and may indicate that the specific region we studied is
less polluted.
4. CONCLUSIONS
Our results represent the first study on metals in core
sediments of Jordanian coastal areas of the Gulf of
Aqaba, Red Sea. The data indicate that the sediments at
most of our sampling sites are uncontaminated. The only
site with significant contamination particularly for Cd
was found at the PLB site likely due to the extensive
industrial activity at this site. The calculated CFs were
found in the following order Cd > Pb > Cr > Ni > Zn >
Cu. The pollution Loading Index (PLI) calculated for
different areas were found in the following sequences:

T. Al-Najjar et al. / Natural Science 3 (2011) 775-782 781
Table 2. Metal concentrations (µg·g−1) in average continental crust used for calculating PLI [34].
Elements Average continental crust Elements Average continental crust
Cr 35 Pb 14.8
Cu 25 Zn 52
Ni 19 Cd 0.1
Table 3. Contamination Factors for surface sediments.
Area Cu Pb Ni Zn Cd Cr
MSS 0.0001 0.0077 0.0003 0.0003 1.2617 0.0005
HA 0.0001 0.0075 0.0008 0.0006 1.0483 0.0005
IA 0.0001 0.0070 0.0015 0.0008 0.9550 0.0002
PLB 0.0008 0.2607 0.0161 0.0077 47.9375 0.0296
TB 0.0001 0.0084 0.0003 0.0000 1.7600 0.0009
Table 4. Concentrations of metals (µg·g−1) in surface sediments worldwide compared to those in the present study.
Location Cu Pb Ni Zn Cd Cr Reference
Gulf of Aqab 0.03 4.07 0.43 0.42 5.25 1.12 Present study
Red Sea, KSA 25.76 92.86 90.79 93.86 3.95 35.36 [6]
Red Sea, Egypt 21.43 51.4 [35]
Al-Hodeidah, Yemen 11.3 3.48 13.25 30 14.2 20.2 [36]
Aegean Sea 9.6 22.3 38.4 75 0.25 35.7 [37]
Gulf of Mannar 57 16 24 73 0.16 177 [28]
South East Coast-India 506.21 32.36 38.61 126.83 6.58 194.83 [2]
Gulf of Mannar 57 16 24 73 0.16 177 [38]
PLB > HA > IA > MSS > TB. The results of this study
could be used as a baseline against which future anthro-
pogenic effects can be assessed and for management
decision to reduce pollution particularly at the PLB site.
5. ACKNOWLEDGEMENTS
We acknowledge the effort of the Marine Science Station in support
this research. We thank Dean of scientific research, Yarmouk Univer-
sity for their support. Our work was supported by the NATO projects
(SfP 982161 and 981883).
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