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Heavy metal concentrations insediments from the coast ofBahrainM. Salim Akhter & Osama Al-JowderPublished online: 21 Jul 2010.

To cite this article: M. Salim Akhter & Osama Al-Jowder (1997) Heavy metalconcentrations in sediments from the coast of Bahrain, International Journal ofEnvironmental Health Research, 7:1, 85-93, DOI: 10.1080/09603129774039

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0960-3123/97/010085-09 � 1997 Journals Oxford Ltd

International Journal of Environmental Health Research 7, 85 ±93 (1997)

Heavy metal concentrations in sediments fromthe coast of BahrainM. SALIM AKHTER and OSAMA AL-JOW DER

Department of Chemistry, University of Bahrain, PO Box 32038, Isa Town, Bahrain

The concentration of lead, zinc, cadmium, nickel, copper and vanadium in the sediments of nineteen

coastal stations in Bahrain were determined by atomic absorption spectrophotometer (AAS). The results

showed widespread occurrence of anomalously high levels of heavy metals owing to pollution, especially,

zinc and lead, and the overall mean value in sediments for Pb, Zn, Cd, Ni, Cu and V of 111, 104, 1.17, 40.5,

15.1 and 21.9 mg/kg, respectively. In certain areas, the concentrations of some of these heavy metals,

especially lead, were much higher. This could be the result of pollution from land-based industrial and

urban sources, namely automobiles, which contribute to the overall pollution in the coastal areas.

Refineries and other industries, as well as sewage effluents, discharge their liquid wastes in the shallow

coastal areas and are sometimes untreated or partially treated. Heavy metal concentrations in areas located

near industries were generally higher than in the other regions of the island. The trend that has been noted

in this study suggests that this pollution, if left unchecked, could pose a threat to mankind and to marine

life. This study represents a limited number of sampling stations in Bahrain. To assess metal pollution in

Bahrain and within the Arabian Gulf, and to establish a more realistic baseline, it is suggested that a more

detailed study of metal concentrations in the sediments from the coastal areas of Bahrain be conducted.

Keywords : sediments; trace metals; pollution; health effects.

Introduction

Prolonged input of trace metals and bio-resistant organic pollutants to coastal waters soon lead

to accumulation in the aquatic ecosystem. As a consequence of long-term input, local sediments

and biota are enriched in these contaminants.

Pollution of coastal marine environments with trace metals is a major concern since it may

lead to deterioration of natural habitats by depleting ecologically sensitive species or eliminating

or tainting commercial species (Reimer et al. 1975, Foster 1976, Forstner 1977, Vernet et al.

1977, Bowen 1977, Schaule and Patterson 1978, Bowen 1979, Kabata-Pendis and Pendis 1984,

Irgolic and Martell 1985, Adriano 1986, Marschner 1986, Arndt et al. 1987, Sansoni 1987,

McKenzie and Sm ythe 1988, Nriagn and Pacyna 1988, Caroli et al. 1989, Markert and Weckert

1989, Markert and Thornton 1990). It also poses a serious health hazard like the one which

developed in the well documented and often cited case of `Minamata disease’ , in which more

than 700 people died or were disabled through eating fish or shellfish contaminated with methyl

mercury (Saha 1972) .

The accumulation of trace metals in bottom sediments occurs to a large extent by adsorption

to sediment particulate material, such as clays, minerals, organic detritus, sulfides, hydrated iron

oxides, and planktonic organisms. Therefore sediments may provide a reliable record of recent

and longterm pollutants input of pollutants.

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86 Akhter and Al-Jowder

In Bahrain, trace metal enrichm ent of marine environm ents may result from a number of

human activities, especially from the petroleum and petrochemical industries, high traffic

density areas, and port activities. The Gulf is naturally a highly stressful environment, even

without the significant input of anthropogenic contaminants. It covers 239 000 km 2 and is

990 km long and 200±300 km in width. The Gulf is shallow, with an average depth of only

35 m, rarely exceeding 100 m. It is almost land-locked because the only connection to the

open water is the Strait of Hormuz, which is only 86 km wide. The turnover and flushing

time have been estimated to be in the range 3 ±5 years, indicating that the pollutants are likely

to reside in the Gulf for a considerable time. The range in coastal sea temperature is

10 ±39ÊC, and the salinity ranges from 38 to 70 ppt (Emergy 1956, Purser and Seibold 1977,

John et al. 1990).

These observations generally apply to the coastal areas of Bahrain. The state of Bahrain is an

archipelago composed of 33 islands located in the Arabian Gulf with a total area of 695 km 2. The

temperature in the coastal areas of Bahrain ranges from 14 to 35ÊC and salinities range from

42 ppt in the northeast to 60 ppt in the northwest and up to 70 ppt in some of the shallow lagoons

along the coast. More detailed information on the State of Bahrain is given elsewhere (Madany

et al. 1988, Akhter and Madany 1993, Madany et al. 1994).

It is of paramount importance to conduct comprehensive investigations on the trace metal

concentrations in the sediments from the Arabian Gulf along the coast of Bahrain that badly

needed is the main purpose of this study. Another objective was to provide baseline

information.

Experimental section

Study areas

The areas under investigation included all the coastal areas around Bahrain, and were

represented by a total of 19 sampling stations (Fig. 1). For the purposes of this investigation,

they were divided into the following six categories: (1) site affected by indusrial effluents and

outfall, including localities in the vicinity of major industries, namely a refinery, a methanol and

ammonia plant, a ship building and repairing yard, an iron pelletizing plant, a reverse osmosis

desalination plant, and an abattoir; (2) site polluted with domestic effluent; (3) major and minor

ports; (4) urban residential areas and public beaches; (5) marinas and mooring areas for local

fishermen; and (6) remote (background) coastal locations that are relatively distant from land-

based sources of oil pollution.

The coastal areas studied are generally shallow tidal regions, and the tidal water amplitude

varies from 0 to about 3 m. This results in poor water exchange and relatively stagnant

conditions in the coastal areas.

Sample collection and analysis

Samples of the finest sediment particles (only fine grained sediment was sampled because

metals are concented in it owing to its high adsorption capacity) were collected from nineteen

different coastal stations in Bahrain (Fig. 1). As the southern part of the island was inaccessible,

therefore no samples were obtained from there. Sediment sampling was carried out only where

the bottom consists of relatively soft and homogenous sands. Plastic containers (bottles or bags)

were used to collect the samples. These containers were washed thoroughly with soapy water

and rinsed thoroughly with distilled water and finally deionized water. A list of the samples, the

sampling location, and descriptions of samples is given in Table 1.

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1000

kmIRAN

SAUDIARABIA

KUWAIT

GATAR

BAHRAIN

Ar a b i a n

G u l f

13

34

910

MUHARRAQ ISLAND

MUHARRAQHIDD

CausewayCauseway

Asry GrycockDesalination

MANAMA

MINA SULMAN

ISA TOWNA’ALI

Causeway Route

11BUDAIYA

JIDDA

18

Causeway toSaudi Arabia

UM AN-NASSAN

JeoelDukhan1

ZELLAQ

Ras al-Barr HAWAR ISLANDS

7

6

5

17

15Gulf PetrochemicalIndustries Company(GPIC)

Silra JettySITRA ISLAND

Aerial RopewayRacecourse

EAST RIFAA

Stadium

HAMED TOWN

WEST RIFFA

Oil pipeline

AWALI19

Plant & Power Station

CausewayNABISALIH

12

8

BAHRAIN

100

km

N

TownAluminium Bahrain (Alba) SmelterBapco RefineryOil WellTropospheric Scatter Station

Al-Areen Wildlife Station

Traffic Police

Airport

Major Road

Heavy metal concentrations 87

Approximately 1.5 g of each sediment sample was dried in an oven at 105ÊC for 24 h and

0.250 g of each dried sample was weighed into a dried, pre-washed Teflon beaker. 10 ml of

concentrated HNO3 and 5 ml HF were added to the sample for digestion. The mixture was

heated slowly until a dried mixture was obtained. Samples were cooled to room temperature and

extracted with 1% HNO3 solution. Samples were filtered until a clear solution was obtained

from each one. A blank solution was prepared following the same procedure. Each sample was

analyzed in triplicate for Pb, Zn, Cu, Ni, Cd, and V, using a PYE-UNICAM, SP-9-800 atomic

Fig. 1. Map showing coastal areas of Bahrain and the location of the sampling sites.

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88 Akhter and Al-Jowder

absorption spectrophotometer (AAS). A com puterized PU 9095, videographic furnace with

autosampler, a PM 8251 chart recorder and a Pu 9090 data computer, interfaced with the

spectrophotometer, were used for the analysis.

Continuum source background correction was used whenever needed.

Quality control assurance

For quality assurance, these analyses were also done using a Baird Atomic Ltd (Model Alpha

4) (AAS) at the Tubli plant. After each analytical run, the calibration curve was displayed on the

screen and a visual check was made for linearity and replication. Prior to each analysis, the

instruments were calibrated according to the manufacturer’ s recommendations. All the standard

solutions (1000 ppm) for Pb, Zn, Cu, Ni, Cd and V were certified and obtained from Fisher

Table 1. List of sampling locations and descriptions of sediments samples

Sample Name of coast Station Description of sample

1 Al-Jazayar beach Al-Jazayar beach Bahrain near

Zallaq

Light brown sand containing small

stones

2 Marina beach Behind Grand Mosque in Manama Soft, fine greyish sediments

3 Galali East of Galali towards Hidd Fine dark grey particles

4 Busatin beach One km north of Muharraq

Causeway

Dark brown particles

5 Askar South of Askar village Fine, sticky, ash-grey sediments

6 Jau South of Jau village Fine grey sand

7 Ad-Dur North of Dur village Fine grey sand

8 Sitra Between south of Sitra and north

of Askar near tanks

Blackish brown sand

9 Manama beach Opposite Hilton Hotel Large grey and brown stones

10 Karanah beach North of Karanah village Dark brown slightly coarse

11 Budaiya beach Abu Subah beach north west of

Bahrain

Very sticky black sediments

12 South Manama Two km south of Tubli Brownish grey sediments

13 Al-Dair West of Dair village Dark brown sediments

14 Asry ± bay side Near Asry dock (bay side) Light brown sediments

15 Near GPIC Towards the southern coast ofSitra (500 m from GPIC)

Greyish black very stickysediments

16 Asry ± open side Near Asry dock (bay side) Brown fine particles

17 Al-Bandar resort Southern side of Sitra near Al-

Bandar resort

Grey black sticky sediments

18 Al-Jasra village Two km south of Saudi Bahrain

causeway

Greyish fine particles

19 Al-Malkiyah Coast of Malkiyah village Brown fine sediments

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Heavy metal concentrations 89

Scientific Company, USA. These solutions were diluted carefully to the required concentrations

with doubly distilled deionized water.

Prior to analysis, standard reference materials obtained from the National Bureau of

Standards, Washington, DC, USA, were also analyzed in order to ensure that our procedures for

sample preparation and analysis were reliable.

Results and discussion

The trace metal concentrations in sediments from various stations in Bahrain are reported in

Table 2. The overall mean values and ranges are as follows:

Cu, 15.1 (0.6±36.9); Zn, 104.0 (12.5 ±191.1); Ni, 40.4 (0.6±68.4); Cd, 1.17 (0.3 ±4.6);

Pb, 111.6 (33.9±343.1) and V, 21.9 (8.6±42.5)

It can be seen from Table 2 that the values obtained for certain industrial areas were high

compared to other regions. For example, the concentrations of zinc, nickel and lead were quite

high for sample 5, which is located near Askar (Fig. 1); and the nickel concentration in this

region was found to be the highest, since this area is located near BAPCO (Bahrain Petroleum

Com pany). The anomalously high lead concentration may be due to the deposition of particulate

Table 2. Mean metal concentrations in sediments in various coastal regions in Bahrain (mg/kg) (seeTable 1, Fig. 1)

Sample number Cu Zn Ni Cd Pb V

1 22.3 110.1 39.0 2.2 84.2 17.0

2 30.5 144.7 65.5 0.8 121.5 18.23 25.0 175.0 59.2 1.3 156.5 17.4

4 12.1 149.3 35.3 0.8 172.5 14.65 26.2 124.3 68.4 0.9 294.9 42.5

6 19.9 157.6 52.2 1.1 103.6 20.17 23.1 186.9 46.6 1.5 89.7 17.4

8 18.2 168.3 64.8 4.6 127.8 32.49 6.7 191.1 43.6 1.2 343.1 16.0

10 12.2 61.6 62.6 0.3 118.3 8.611 36.9 85.6 52.8 1.3 105.4 30.712 12.1 139.1 19.5 2.6 110.9 12.3

13 4.9 76.9 32.8 0.5 98.2 17.614 0.6 12.5 25.3 0.8 45.0 31.4

15 18.6 69.8 63.1 1.3 38.4 24.616 3.5 21.6 34.3 0.6 42.5 24.7

17 10.6 53.4 ND 0.4 49.0 30.318 1.1 26.4 2.9 ND 34.8 21.8

19 2.2 22.0 0.6 ND 33.9 19.4

Mean 15.1 104.0 40.5 1.17 111.6 21.9Min. 0.6 12.5 0.6 0.3 33.9 8.6

Max. 36.9 191.1 68.4 4.6 343.1 42.5SD 2.4 17.4 6.7 0.16 22.0 7.2

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90 Akhter and Al-Jowder

lead owing to heavy motor traffic in these regions (Foster 1976, Sadiq and Zaidi 1984, Adriano

1986, Fowler 1988, Akhter and Madany 1993, Madany et al. 1994). Lead pollution in these

areas could be the result of marine activities such as boating.

The cadmium concentration of 4.6 mg/kg, in sample 8, is the highest value obtained (Table 2).

This could be the result of oil spills and oil transportation in the neighbour ing regions (Schaula

and Patterson 1978, Sadiq and Zaidi 1984, Fowler 1988), as motor oil contains small amounts

of cadmium. High concentration of zinc and copper may be due to automobile emission and the

dumping of wastes (Foster 1976, Sadiq and Zaidi 1984, Adriano 1986, Fowler 1988, Akhter and

Madany 1993). For example the high value, of zinc for sample number 9 (Table 2) could be due

to the high density of traffic in the region.

Sediments as Askar (sample 5) contained relatively high concentrations of vanadium

suggesting petroleum contamination. More likely, the elevated levels of Pb, Cu, Zn and Cd are

mainly due to the site’ s proximity to the densely populated and industrialized north east sector

of Bahrain. Similar statements can be suggested for samples 8, 11, 14, and 17. The vanadium

concentration is quite high compared to nickel, and because the two metals are related to oil

pollution, these values suggest that the source of nickel contamination could possibly be

automobile emissions (Foster 1976, Sadiq and Zaidi 1984, 1985, Fowler 1988, Akhtar and

Madany 1993, Madany et al. 1994).

On the other hand the values of the trace metal concentrations (samples 18 and 19) obtained

from villages like Al-Malkiyah and Al Jasra were very low in comparison to other coastal areas.

As these villages are located far from any industrial activity, we would not expect them to be

polluted. Owing to the scarcity of traffic in this region lead pollution is expected to be minimal,

and the values of 34.8 mg/kg for sample 18 and 33.9 mg/kg for sample 19 confirm this

assumption.

There are several reasons for the high concentrations of these heavy metals. The textural

differences among the sediment from different coastal areas may account partially for metal

enrichment in the sediments. Harbour and port activities in the sampling regions are

undoubtedly among the major factors contributing towards the metal pollution. In addition large

quantities of oil are being discharged from cleaning of oil tankers into coastal waters, and

appreciable amounts of some heavy metals find their way into the water and the sediments. The

Arabian Gulf, in particular, has been subject to inputs of trace metals from a variety of sources,

and it has been estimated that oil pollution in the Gulf represents 4.7% of the total oil pollution

in the world (National Research Council 1985); recently the quantities have increased even

more. In the first place, over 30% of the world’ s marine transport of oil across the waters of the

Gulf to load crude oil from the 25 major oil terminals. These activities which are accompanied

usually by discharge of ballast water, dirty bilge, sludge, and stop oil (Linden et al. 1990) are

potential sources of oil pollution. In the second place, tanker accidents due to wars are

considered the largest source of spilled oil, and only during the period May 1981 and June 1987,

329 war-related incidents were reported (Linden et al. 1990). Recently, the oil spill due to the

Gulf war discharged approximately 11 million barrels into the Gulf (Price and Sheppard 1991) .

Third, offshore oil exploration, transport, and accidents are another source of oil pollution. For

example, the blow-out of the Iranian Nowruz oil field in February 1983 poured approximately

4000 bbl/day of crude oil, causing the death of large numbers of marine animals and sea birds

(Begley et al. 1983, Sadiq and Zaidi 1984). Finally, land-based industrial and urban sources also

contribute to the overall pollution in the coastal areas. Refineries and other industries, as well

as sewage treatment plants, discharge their liquid waters into the shallow coastal waters, and

they are sometimes untreated or partially treated.

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Heavy metal concentrations 91

The concentrations of cadm ium, lead, zinc and nickel found in the sediments in this study

were compared to the data reported in the literature (Table 3). The concentrations of cadm ium

and nickel found in this study were lower than those in Saudi Arabia and Kuwait Bay (Sadiq and

Zaidi 1984) whereas the values for zinc and lead were much higher. The zinc concentrations in

the sediments of the coastal regions of Bahrain were generally much higher than the values

reported for other parts of the world, except for Taiwan (Table 3).

The present study was limited to small areas at a few locations in Bahrain. However it is

suggested that a more detailed investigation of metal concentration in the sediments from the

coastal regions of Bahrain should be conducted. Further, little was done to determine the source

of trace metal pollution in this study and this aspect should not be overlooked in future

investigation.

C onclusion

The data obtained in the present study indicate widespread occurrence of anomalously high level

of heavy metals owing to pollution, especially Zinc and Lead. This could be the result of

pollution from land-based industrial and urban sources, namely automobile to the overall

pollution in the coastal areas. Heavy metal concentration in the areas near industries were

generally higher than in the other regions of the island. The trend that has been noted in this

Table 3. Metal concentration (mg/kg dry sediments) in the sediments from various parts of the world

Areas Cd Pb Zn Ni Cu V Reference

Arabian Gulf, Bahrain

(present study)

1.2 111.6 104.0 40.6 15.1 21.9

Arabian Gulf 0.04 13.5 N/A N/A 17.6 27.4 (Flower 1988)Bahrain* 0.04 24.0 N/A N/A 11.2 14.0

Arabian Gulf, Saudi Arabia 5.0 4.2 22.6 64.6 N/A N/A (Sadiq and Tahir 1985)

Arabian Gulf, Kuwait Bay 3.9 48.0 123.0 139.0 N/A N/A (Anderlini et al. 1982)

Lebanon coast 3.8 104.6 154.6 38.4 N/A N/A (Shiber 1972)

Mediterranean Sea, Israel 2.2 19.7 18.2 29.0 N/A N/A Roth and Hornung 1977)

Torbay English coast 0.7 65.7 42.0 15.0 N/A N/A (Taylor 1974)

Harbour Island,

Gulf of Mexico

1.1 9.0 28.0 10.9 N/A N/A (Roth and Honung 1977)

Portsmouth Harbour, UK 3.3 114.0 210.0 30.0 N/A N/A (Soulby et al. 1978)

New South Wales, UK 2.5 53.0 144.0 24.0 N/A N/A (Shiber 1972)

North Sea, UK 0.8 238.0 197.5 22.0 N/A N/A (Shiber 1972)

Kaohsiung Harbour, Taiwan 1.8 576.0 3514.0 285.0 N/A N/A (Shiber 1972)

Narraganselt Bay, USA 2.5 81.0 168.0 34.0 N/A N/A (Eisler et al. 1977)

N/A = not available.

*Upper line = Askar (east coast of Bahrain); lower line = Al-Zallaq (west coast of Bahrain).

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92 Akhter and Al-Jowder

study suggests that this pollution, if left unchecked, could pose as threat to mankind and to

marine life. However, these conclusions can not be stated unequivocally; more investigation is

needed and authors are exploring this problem.

Acknowledgement

The author wishes to acknowledge the support from University of Bahrain through research

grant (SC-9404). The author also likes to thank EPC Bahrain for their help in experimental

work, and Mr Essa Fateh for typing this manuscript.

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