Heavy metals pollution in sediment cores from the Gulf of Aqaba, Red Sea

doi:10.4236/ns.2011.39102

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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: [email protected]

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

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

0.02

0.03

0.04

MSS1

MSS2

MSS3

HA1

HA2

HA3

IA1

IA2

IA3

PLB1

PLB2

PLB3

TB1

TB2

TB3

interval sites

concentration (µg.g)

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)

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)

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)

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)

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)

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)

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:



123 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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