Journal of Marine Systems 78 (2009) 1–8

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Journal of Marine Systems

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Distribution and characteristics of polycyclic aromatic hydrocarbons (PAHs) insediments of Hadhramout coastal area, Gulf of Aden, Yemen

Alaa R. Mostafa a,⁎, Terry L. Wade b, Stephen T. Sweet b, Abdel Kawi A. Al-Alimi c, Assem O. Barakat a

a Department of Environmental Sciences, Faculty of Science, Alexandria University, 21511 Moharam Bek, Alexandria, Egyptb Geochemical and Environmental Research Group, Texas A&M University, College Station, Texas, TX 77845, USAc Department of Environmental Sciences, Faculty of Environment and Marine Biology, Hadhramout University, Yemen

⁎ Corresponding author. Fax: +2 03 4253477.E-mail address: alaa_mostafa@link.net (A.R. Mostafa

0924-7963/$ – see front matter © 2009 Elsevier B.V. Adoi:10.1016/j.jmarsys.2009.02.002

a b s t r a c t

a r t i c l e i n f o

Article history:

To assess the status of poly Received 11 April 2008Received in revised form 3 January 2009Accepted 3 February 2009Available online 13 February 2009

Keywords:Polycyclic aromatic hydrocarbons (PAHs)Marine sedimentsGulf of Aden, Yemen

cyclic aromatic hydrocarbon (PAH) contamination in sediments of Hadhramoutcoastal area, Gulf of Aden, Yemen, 17 surface sediment samples were collected in March–April 2005 andanalyzed for PAHs with 2–6 benzene rings by gas chromatography–mass spectrometry (GC-MS).The concentrations of PAHs in surface sedimentswere in the range of 2.2–604ngg−1 (average value:82.4 ngg−1).PAHs contamination is highest in proximity to harbour activities, near Al-Dhabah petroleum terminal and urbanareas. Comparison of the concentration rangewith aworldwide surveyof sedimentary PAHconcentrations rankedPAH contamination in Hadhramout coastal sediments as low to moderate. Assessment of PAH sources inHadhramout coastal sediments suggested that they originated largely from petrogenic sources. PAHs of pyrolyticoriginwere found in sediments fromurbanized areas. Adverse effects on benthic communities are not expected atthe levels of PAHs contamination observed from harbour and industrial areas.

© 2009 Elsevier B.V. All rights reserved.

1. Introduction

The contamination of the marine environment by organic andinorganic pollutants in the Gulf of Aden and Arabian Sea is a majorconcern of all countries in the region. There is a need for baseline datato determine the extent of environmental contamination.

Because of the potential impact of the pollution from anthropo-genic sources on marine life and fisheries, it is important to know theextent of the contamination, how it may affect marine life, and howlong the effects may last. The coastal waters of Yemen arecharacterized by its high primary and secondary productivity makingit a basic feeding and nursery ground for marine species.

More than 600 species of marine organisms have been recorded inYemen waters (MFW, 2001). The extent of contamination of themarine environment in the Republic of Yemen coastal area bypersistent organic pollutants and heavy metals is largely unknown.Untreated domestic wastewater, industrial wastewater, and agricul-tural drainwater, run-off during rainy periods, ship and boat traffic, oiltransportation, oil spillage, and atmospheric fallout are all potentialsources of contamination (Heba et al., 2000).

Coastal sediments act as temporary or long-term sink of naturaland anthropogenic organic matter from land-based sources. Hydro-carbons are important components of the land-derived organic inputs

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ll rights reserved.

to coastal areas. These compounds are readily adsorbed ontoparticulate matter, and bottom sediments act as a reservoir for thesehydrophobic contaminants (Budzinski et al., 1997).

The composition of hydrocarbon compounds found in sedimentsreflects the relative contributions from different sources: biogenic,diagenetic, petrogenic and pyrogenic (Lipiatou et al., 1997; Hostettleret al., 1999).

PAHs sources can be divided into three main classes according totheir characteristic fingerprints. One important input of PAHs into themarine environments is from pyrogenic sources, that is combustion oforganic matter, anthropogenic industrial activity, or natural fires.These sources give rise to complex mixtures of PAHs characterized bya high abundance of parent PAHs and a low proportion of alkylatedPAHs. The second group is petroleum hydrocarbons from petroleumtransportation, off-shore exploitation, oil spills or natural oil seeps.The composition of petroleum hydrocarbons is very complex and ischaracterized by a high abundance of alkylated PAHs. Finally, a fewcompounds may have a diagenetic origin. Most frequently detected,perylene can be derived from biogenic precursors via short-termdiagenetic processes. Reducing sediments, which receive significantamounts of terrestrial organic matter, contain relatively high amountsof perylene. Perylene could also derive from aquatic material ordiatoms and during combustion processes (Venkatesan, 1988).

Different sources (pyrolytic, petroleum and diagenetic hydrocar-bons) give rise to different characteristic PAH patterns and it istherefore possible to estimate the major processes that generate thesecompounds (Soclo et al., 2000).

2 A.R. Mostafa et al. / Journal of Marine Systems 78 (2009) 1–8

PAHs formed during the pyrolysis of virtually all organic matterand are ubiquitous organic contaminants in aquatic sediment. Theiracute toxicity and sublethal effects to aquatic organisms, including themutagenic and genotoxic potential of some PAHs through the foodchain, has generated interest in the study of their composition anddistribution in the environment (Oros and Ross, 2004; Hartmannet al., 2004; Kannan et al., 2005; Viganò et al., 2007).

PAHs from pyrolytic processes are more strongly associated withsediments and much more resistant to microbial degradation thanPAHs of petrogenic origin (McGroddy and Farrington, 1995; Gustafs-son et al., 1997).

The present study is the first investigation of the current status ofPAHs concentration in surface sediments of Hadhramout coastal area.The results provide a valuable reference data set for environmentalmanagers.

2. Materials and methods

From March to April 2005, seventeen surface sediment samples(0.1–10 cm)were collected from seventeen sites in five regions using aPeterson grab sampler (EPA, 2001). The sediment samples werecollected to cover the coastal area of Hadhramout which is an area ofintense industrial and urban activities. In addition, one referencesediment sample was collected from Ras Sharmah beach (a protectedarea) which is located in the extreme eastern region of the Gulf ofAden (Fig. 1). During this study special precautions were taken toavoid sample contamination during collection, transportation, pre-servation and laboratory analyses. To prevent contamination of tools,instruments and other materials, which may come in contact with thesamples, only clean glassware and other materials of high purity wereused. In general, all sampling procedures were carried out accordingto Wade et al. (1994). Collected samples were frozen on dry ice andtransferred to the laboratory for processing. Sample preparation andanalysis methods have been described in Wade et al. (1998).

Aliquots of the homogenized samples were extracted and analyzedfor PAHs at the Geochemical and Environmental Research Group,Texas A&M University.

Fig. 1. Location map o

Briefly, about 10 g of freeze-dried sediment was extracted withdichloromethane (DCM) using Accelerated Solvent Extractor (ASE)The surrogates d8-Naphthalene, d10-Acenaphthene, d10-Phenan-threne, d12-Chrysene, d12-Perylene were added to the samples priorto extraction. Concentrated extracts were fractionated with alumina/silica gel (80–100 mesh) column chromatography. Target analyteswere eluted from the column with 200 mL of 1:1 pentane–dichloromethane (PAH/PCB/pesticide fraction). This fraction wasthen concentrated to 1 mL using Kuderna–Danish concentratedtubes heated in a water bath at 60 °C to 70 °C.

Polycyclic aromatic hydrocarbons (PAHs) were analyzed with aHewlett Packard 5890 gas chromatograph equipped with a 5970Bmass selective detector (GS/MS) using a 3 m×0.25 mm (i.d.) DB-5fused silica capillary column (J & W Scientific) and operating in theselected ion mentoring (SIM) mode. Instrument conditions, identifi-cation quantification and QA/QC procedures used for GS/MS analyseshave been described elsewhere (Wade et al., 1998). Matrix spikes,laboratory sample duplicates, and laboratory blanks were processedwith each batch of samples (10 samples/batch) as part of thelaboratory internal quality control. All the quality control proceduressatisfied their acceptable ranges. Recoveries ranged from 60% to 105%.Reproducibility of analyses was tested by four replicate analyses ofsediment extracts; it ranged from 3.2% to 10.1% of relative standarddeviation. Standard Reference Materials (SRMs), provided by theNational Institute of Standards and Technology (NIST) were analysedto monitor the performance of the analytical methods. The recoveriesof PAHs in a certified marine sediment SRM 1941a (NIST) were N83%The method detection limits for the low molecular weight PAHs(MWb202) and highmolecular PAHs (MWN202) were in the range of0.5–1.2, 1.0–2.0 ng g−1dry weight, respectively. Known quantity ofinternal standard fluorene-d10 and benzo[a]pyrene-d12 were added tothe samples prior to the instrumental analysis in order to quantify thePAH concentrations. The quantification limit for individual PAHspecies was set at five times the detected amount in the proceduralblank. Procedural blanks for PAHs normally gave ng g−1 total PAHs persample, corresponding to ng g−1 total PAHs. The compoundidentification is based on a comparison of the retention times of thetarget compounds contained in the calibration standards with the

f the study area.

Table 1Concentrations of PAH, % TOM and silt/clay in surface sediments of Hadhramout coastal area, Gulf of Aden.

No. Activity % TOM Silt/clay

∑PAH(ng g−1)

∑EPA-PAHs(ng g−1)

Alk/Nalk

HMW/LMW

Ph/An Chr/BaA

Fl/Py

Fl/(Fl + Py)

Py/BaPy

∑COMB/EPA-PAH

IND/(IND + BghiP)

Perylene(ng/g)

1 Old harbour – Sewage discharge –

fishing port0.11 0.66 19.7 9.8 1.32 0.02 24.75 0.00 0.74 0.42 190.0 0.03 NA 0.03

2 East of Burum 0.11 3.07 2.2 2.1 NA 1.61 2.11 0.55 0.05 0.05 20.0 0.60 NA 0.093 Fishing port-discharging waste

(domestic and industrial)0.15 4.4 174 47.8 2.61 0.37 2.62 1.08 1.10 0.52 2.16 0.59 0.51 1.59

4 Main harbour 0.24 7.4 197 48.5 2.89 0.50 2.03 1.14 1.13 0.53 1.36 0.71 0.44 0.775 Stranded wrecks 0.18 2.8 64.6 19.7 2.47 0.46 7.53 1.01 1.12 0.53 1.09 0.56 0.40 0.406 Electrical power station, Fishing

industries0.14 1.7 55.9 33.8 0.22 2.58 2.92 2.44 0.92 0.48 0.61 0.83 0.42 1.67

7 Intermittent stream 0.13 1.6 12.8 6.2 0.63 0.91 21.50 2.05 1.05 0.51 2.33 0.69 0.51 0.078 Intermittent stream, fishing

industries0.13 1.66 16.5 6.2 1.46 0.28 13.40 1.82 1.05 0.51 1.0 0.42 0.52 0.08

9 Petroleum terminal 0.13 7.04 37.7 22.5 1.13 0.06 240.0 0.03 1.46 0.59 260.0 0.06 NA ND10 Petroleum terminal 0.13 6.38 17.9 5.2 2.63 0.09 12.57 3.00 0.95 0.49 190.0 0.14 NA 0.0611 Petroleum terminal (west) 0.13 5.69 126 24.2 11.1 0.07 4.15 1.45 1.24 0.55 0.83 0.10 NA 0.1112 Petroleum terminal (east) 0.37 2.27 13.6 8.1 0.82 0.18 2.79 1.80 1.22 0.55 360.0 0.19 NA 0.0913 Petroleum terminal (east) 0.33 7.62 8.50 4.3 1.43 NA 5.12 0.00 1.00 NA NA NA NA ND14 Intermittent stream (east)

and sewage discharge0.13 1.29 604 199 1.92 0.98 1.54 1.40 1.09 0.52 2.69 0.85 0.45 3.14

15 Fishing port – sewage discharge 0.10 1.39 21.5 7.2 2.75 0.01 4.27 0.00 1.67 0.63 90.0 0.03 0.00 0.0216 Sewage discharge 0.10 1.7 22.3 5.0 4.95 0.01 7.30 0.00 111 0.99 NA 0.02 NA 0.0117 Protected area 0.13 1.69 6.0 2.5 1.38 0.04 4.92 0.00 1.00 0.50 110.0 0.09 NA ND

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sample set to confirm GC/MS system performance and calibration.Concentrations of the target analytes are reported as nanograms/gram (ng g−1) based on dry sediment weight.

Total organic mater content (TOM)was determined by the methodof loss in weight by ignition described by Byers et al. (1987).Sediments grain size was determined by the procedure of Folk(1974), utilizing sieving to separate gravel and sand fraction from theclay and silt fractions. The latter fractions were subsequentlyseparated by pipette (settling rate) method. To examine whetherOM and sediment grain size were the major factors controlling thedistribution of PAHs in the study area, correlation analysis wasperformed using SPSS 11.0 for Windows.

3. Results and discussion

The results of PAHs (∑46PAHs) and % TOM and fine fraction insurface sediment of Hadhramout costal area is presented in (Table 1).Sediment grain size fractions were classified as fine (silt-clay;b0.063 mm), sand (0.063–2 mm). Sand generally predominates(N92%) in bottom sediments. Total organic matter (%TOM) contentsrange between 0.10% and 0.37%, with average value of 0.16%. Nostatistically significant correlation between % TOM and grain sizefractions was detected.

The processes controlling the level of PAHs in the sediments arecomplex. It has been demonstrated that the nature of the sedimentsinfluences the distribution and concentration of PAHs. The distribu-tions of PAHs in the sediments are affected by chemical composition ofthe sediments such as organic matter and clay content. Sedimentswith high organic content were characterized with high values ofPAHs (Yang, 2000).

In the present study the regression analysis was completed toinvestigate the relationship between the concentration of∑PAHs andthe percentage of organic matter and fine fraction. The linearregressions between these parameters show no significant correlationof ∑46PAHs with total organic matter (r2=−0.06) or silt-claycontent (r2=−0.03).

Mostafa et al. (2003) demonstrated similar results of no significantcorrelation for sediments from the western harbour of Alexandria.These studies, including the present work, suggest that the distribu-tion and concentration of PAHs in sediments is determined more bydirect input, rather than by the type of the sediment found locally.

Data in Table 1 show the geographical distribution of PAHsconcentration in surficial bottom sediment of the Hadhramout costalarea. Total concentrations of PAHs vary from 2.2 to 604 ng g−1 drysampleweight (average value: 82.4 ng g−1). Among the areas surveyed,Al-Sheher (station14) showed thehighest contentof PAHs (604ngg−1)followed by Al-Mukalla at Stations 3 and 4 (174 ng g−1 and 197 ng g−1

respectively). Station 14 is located near the mouth of the Wadi Al-Asiaintermittent stream draining in the east and Al-Sheher harbour in thewest. The pollution in this area is affected by agriculture runoff and highurban impact with contamination due to the input of untreated sewagewhich is directly discharged to the sea through a number of sewer pipesin addition to the pollution from Al-Sheher harbour where residentialpopulation is high and small industrial shipping activities are intenseand activities of fishery and fish processing are common.

Stations 3 and 4 are located inside the harbour zone of Al-Mukallawhere heavy traffic of tankers and commercial cargo boats arecommon. The stations are also located near the ship lift, dry dock aswell as the naval ships facilities. Al-Mukalla city is one of the mainindustrial areas along the coastal area of Hadhramout, having largefish processing works, power stations, and petroleum and chemicalstorage facilities in addition to numerous industrial facilities. Al-Mukalla harbour receives between 9000 and 10,000 tons of petroleumproducts per week. They are in the form of petrol, diesel, gas, oil andkerosene for domestic use in the region (EPA, 2003).

Sediment samples from relatively pristine region such as Burum,Shiher Coast and Ras Sharmah contained less PAH content.

The geographic distribution of PAHs in the coastal area ofHadhramout indicates that PAHs contamination in the coastalenvironment is closely related to oil spills at Al-Sheher Oil Terminaland deblasting tankers and passing ships are major sources con-tributing to PAHs contamination. The other sources include thesewage effluents of oil supply stations, and other service installationsthat are mainly located at Al-Mukalla port.

All surficial sediment samples show higher proportions of lowmolecular weight PAH (2–3 rings). The high molecular weight (4–6rings) PAH (HMW) are dominated only in Al-Mukalla port and Shihercoast where the Electrical Power Plant of Khalaf Suburb (in Al-Mukallaport zone) is located (Fig. 2).

Also station 14 in Al-Sheher area has high contamination of HMWcompound compared with stations in Al-Mukalla and Shiher coastareas. The concentrations of two, three, four, five and six ringed PAHsfrom different sites of Hadhramout coastal area are illustrated in Fig. 2.

Fig. 3. Distribution of alkylated/non-alkylated and HMW/LMW PAH ratios in thesediments samples of Hadhramout coast.

Fig. 2. Distribution of LMW PAH (2–3 ring PAH) and HMW (4–6 ring PAH).

4 A.R. Mostafa et al. / Journal of Marine Systems 78 (2009) 1–8

In general, low molecular weight PAH species (LMW) with 2–3rings originate from petroleum products, incomplete combustion offossil fuels and biomass at low to moderate temperature and naturaldigenesis, while Pyrogenic (Pyrolytic) procedures mainly generatehigh molecular weight (HMW) PAH components with 4 or more ringsat high temperature (Yuan et al., 2001; Mai et al., 2002).

3.1. Composition and source identification of PAHs

Compositions and relative abundance of individual PAHs inmost ofthe investigated sediments were more or less quite similar (Fig. 2),except for stations 2, 6, 7 and 14 where the four to six-ring PAHs werepredominant. Similarity of PAHs distribution suggests that the PAHcontamination in the bulk of Hadhramout coastal sediments comesfrom similar petrogenic sources.

Among all 46 PAHs, naphthalenes, fluoranthene and phenan-threnes were predominant species and accounted for approximately21.26%, 6.19% and 2.37% of total PAHs, respectively in samples frommost of the sites. On the other hand, indeno[1,2,3-cd]pyrene, benzo[ghi]perylene, benzo(a)anthrarathene, chrysene were prevalent insediments at stations 2, 6, 7 and 14 (Table 1).

The PAH congener distribution varies with the production sourceas well as the composition and combustion temperature of the organicmatter. Molecular indices based on ratios of concentrations selectedPAHmay be used to differentiate PAHs from pyrogenic and petrogenicorigins. Six specific PAH ratios were calculated: Ph/An, Fl/Pyr, Chr/BaA, Flu/(Fl+Py), InP/(InP+BgP), and Py/BaP. To estimate the originof the PAHs in sediment samples of Hadhramout coastal area, theHMW/LMW ratio (the sum of the low molecular weight PAHconcentrations to the sum of higher molecular weight PAH concen-trations; i.e., Naph+Aceph+Ace+Fl+Phe+An+Fl+Py+BaA+Chr+BbF+BkF+BaP+Inp+DBA+BgP) was determined.

The abovemolecular indices were used recently by others to assessand determine the origin of PAHs observed in various environments(Woodhead et al., 1999; De Luca et al., 2005; Qiao et al., 2006; Yimet al., 2007).

The ratios of alkylated/non-alkylated and HMW/LMW (highmolecular weight/low molecular weight) are widely used diagnosti-cally. Alkylated PAHs are found mainly in petroleum and petroleum

products. Refined petroleum products, in particular, consist primarilyof LMW PAHs and alkylated PAHs. Pyrogenic processes, such ascombustion of coal, oil and wood, pyrolysis, industrial activator fires,mainly produce non-alkylated PAHs and HMW PAHs (Baumard et al.,1998; Yuan et al., 2001). The ratios of alkylated/non-alkylated PAHsand HMW/LMW PAHs can therefore be used as indicators to definethe sources of PAHs (Budzinski et al., 1997).

The higher alkylated/non-alkylated and lower HMW/LMW PAHratios in sediment samples from Burum (Station 1), Al-Dhabah(Stations 9, 10, 11 and 13), Al-Sheher (Stations 15 and 16) and Ras-Sharma (Station 17) indicate that the major source of PAH pollutionwas contributed by petroleum input (Fig. 3). This is likely to be due toinputs of hydrocarbons from shipping (e.g. ship discharges and oilspills into the coastal area of Hadhramout). Some sediment samplesfrom Burum (Station 2), Al-Mukalla (Station 6), Shiher (Station 7) as

Table 2Characteristic values of selected molecular ratios for pyrolytic and petrogenic origins of PAHs.

Pyrolytic origin Petrogenic origin This study References

HMW/LMW High Low 0.1–2.58 Sicre et al. (1987); Budzinski et al. (1997)Alk/Nalk Low High NA–11.1 Prahl and Carpenter (1983)Ph/An b10 N15 NA–24.75 Soclo (1986); Baumard et al. (1998)Chr/BaA b1 N1 0.0–3.0 Parlanti (1990); Soclo et al. (2000)Fl/Py N1 b1 NA–1.67 Sicre et al. (1987); Baumard et al. (1998)Fl/(Fl+Py) N0.5 b0.5 0.05–0.63 Budzinski et al. (1997); Gogou et al. (1998)Py/BaPy N10a NAb NA–2.69 Macias-Zamora et al., 2002

LMW/HMW: sum of (Naph, Aceph, Ace, Fl, Ph and An,) concentrations against sum of (Fl, Pyr, BaA, Chr, BbF, BkF, BaP, Inp, DBA and BgP) concentrations. Alk/Nalk: sum of alkylatedPAH concentrations against sum of non-alkylated (parent) PAH concentrations. Ph/An: concentration of Phen against concentration of Ant. Fl/Py: concentration of Fl againstconcentration of Py. Fl/(Fl + Py): concentration of Fl against sum of concentrations of Fl and Py. By/BaP: concentration of Py against concentration of BaP.

a From urban origin.b NA, not available.

5A.R. Mostafa et al. / Journal of Marine Systems 78 (2009) 1–8

well as Al-Sheher (Station 14) have relatively lower concentrations ofalkylated PAHs and higher amounts of HMW PAHs (Fig. 3), indicatinga greater proportion of pyrogenic PAHs in these samples. Anabundance of high molecular weight PAHs was also typicallyencountered in atmospheric particles and urban aerosols (Sicre etal., 1987). The relatively low alkylated/non-alkylated and low HMW/LMW PAH ratios in the other samples (Fig. 3) may result from theoccurrence of petroleum in addition to pyrolytic inputs.

The Phe/An index reflects that phenanthrene (Ph) is morethermodynamically stable than anthracene (An). Because of theirdifferent physico-chemical properties, they might behave differentlyin the environment with characteristic Ph/An values for theidentification of the PAH origin. Similarly, fluoranthene (Fl) is lessthermodynamically stable than pyrene (Py); they are often associatedwith each other in natural matrices and a predominance of Fl over Pyis characteristic of a pyrolytic process, while in petroleum-derivedPAHs, pyrene is more abundant than fluoranthene. Generally, a Ph/Anratio b10 and Fl/Py ratio N1 indicates that the contamination by PAHsresults from a combustion process (Soclo et al., 2000). Nevertheless,for both ratios, the limits between the two processes are not preciseand the two indices must be considered simultaneously to provide agood estimate of the different PAH sources (Budzinski et al., 1997 andreferences therein). Some typical values of these indices are given inTable 2.

Some of the investigated samples exhibit pyrolytic input (Table 1,Fig. 4). Phenanthrene to anthracene ratios in the sediment samplesconsistently demonstrate the classical value of pyrogenic sources(b10). However, Fl/Py ratio showed slightly higher value than otherreports. Sediment samples with Ph/An N10 and Fl/Py b1 showedstrong petrogenic origin. Sediment samples with Ph/An b10 and Fl/Py

Fig. 4. Ratio of Phenanthrene (Ph)/ anthracene(An) against fluoranthene (Fl) /pyrene (Py).

b1 were characteristic of a mixed pattern of pyrolytic and petrogeniccontamination. The different ratios might also relate to the degree ofphoto-degradation or biodegradation and also to grain size of thesediment samples (Tam et al., 2001).

Typical combustion origin (COMB) PAHs can be represented by thesum ofmajor combustion specific compoundswhich are fluoranthene,pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-c,d)pyrene and benzo(g,h,i)perylene (Prahl and Carpenter, 1983). The ratio COMB/∑EPA-PAHs was low to moderate (0.0–85) in most of the sediment samplesfrom the coastal area of Hadhramout indicating that there is noextensive combustion activities in the study area except at station 6 inAl-Mukalla harbour (0.83) and station 14 near the mouth of Wadi Al-Sheher intermittent stream draining the Al-Sheher valley (0.85). Fig. 5illustrates the distribution of COMB/∑EPA-PAHs, HMW/LMW andalkylated/non-alkylated PAHs and confirmed the view of a generalpetrogenic origin for PAHs in the sediments of Hadhramout coastalarea, whereas the pyrolytic origin is more commonly found for PAHsin sediments of stations 2, 6, 7 and 14.

3.2. Perylene

In addition to pyrolytic and petrogenic sources, perylene is alsoproduced by in situ degradation of biogenic precursors (Venkatesan,1988; Baumard et al., 1998). Indeed, perylene is probably the mostimportant diagenetic PAH encountered in sedimentary environmentsand, thus a high abundance of perylene relative to the other PAHs canindicate an important natural origin of the compound. The highestconcentrations of perylene were observed in sediments near themouth of Wadi Al-Aisa intermittent stream draining the Al-Aisa valley(Station 14). The large amount of perylene found in this near shoresediment was believed to originate mainly from terrestrial input.Perylene has been frequently associated with inputs from rivers andestuaries (Laflamme and Hites, 1978; Baumard et al., 1998). Theseauthors have suggested that concentrations of perylene which arehigher than 10% of the total penta-aromatic isomers indicate aprobable diagenetic input whereas those in which perylene less than10% indicate a probable pyrolytic origin of the compound. In thepresent study perylene was studied in all sediment samples and itsconcentration ranged from ND to 3.14 ng g−1 dw (Table 1).Concentrations of perylene relative to the penta-aromatic isomersindicate most of the values are less than 10%, indicating a pyrolyticorigin. High values are, 13–50%, observed in Al-Mukalla Harbour(Stations 3 and 6) and Al-Dhabah (Station 10), indicating diageneticorigin for the presence of perylene.

3.3. A comparison of PAHs in sediment

A comparison of PAHs in sediment of Hadhramout coastal areawith published sediments data is given in (Table 3). A quantitativecomparison across reported PAH data is difficult because of variances

Fig. 5. Distribution of COMB/∑EPA-PAHs, HMW/LMW and alkylated/non-alkylated PAHs.

6 A.R. Mostafa et al. / Journal of Marine Systems 78 (2009) 1–8

in the number and type of individual species determined in eachstudy, the sediment fraction analyzed, and the analytical methodsused (Ünlü and Alpar, 2006).

According to Baumard et al. (1998), PAH contents can be describedas low, moderate, high and very high when∑PAH concentrations are0–100, 100–1000, 1000–5000 and N5000 ng g−1, respectively. Thecomparison of the ∑PAH levels in the present study are lowcompared with the international studies worldwide. All stationsexcept 3, 4, 11 and 14 have PAHs concentrations b100 ng g−1 and areindicative of low contamination, whereas values higher than 1000 ngg−1 correspond to chronically polluted industrialized areas andharbour. Stations 3, 4, 11 and 14 had PAHs concentrations of 174,197, 126 and 604 (ng g−1) respectively. On the basis of classificationadapted by Baumard et al. (1998), the sediments from the Hadhram-

Table 3World-wide concentrations of ∑PAHs in surface sediments (ng g−1 dw).

Location ∑PAHs

Tabasco State, Mexico 454–3120Gulf of Mexico, USA 3–3230 (Saudi Arabia, Gulf 11,000–6,West Mediterranean Sea 1.5–20,44Mediterranean Sea 14.6–158.Santos Harbour, Brazil 80–42,39Izmit Bay, Turkey 2500–25,Black Sea 7–640 (∑Santander Bay, Northern Spain 20–25,80Sochi, Black Sea, Russia 61.2–368Black Sea, Ukraine 66.9–635Coastline, Black Sea, Ukraine 7.2–126 (Western Harbour, Alexandria, Egypt 8–131,150Hsin-ta coastal area, Taiwan 98.1–204Gao-Ping River, Taiwan 8–356 (∑Caspian Sea sediments, Iran 94–1789Caspian Sea sediments, Russia 6–345 (∑Caspian Sea sediments, Azerbaijan 338–2988Tianjing, China 787–1,943Gulf and the Gulf of Oman, Oman 1.6–30 (∑Gulf and the Gulf of Oman, Bahrain 13–6600Gulf and the Gulf of Oman, Qatar 0.55–92 (Gulf and the Gulf of Oman, UAE 0.6–9.4 (∑Suez Gulf. Egypt 158–10,46Gemlik Bay, Turkey 50.8–13,4coastal areas, China 189–637Meiliang Bay, Taihu Lake, China 1207 to 4Daliao River watershed, China 61.9–840.Marine environment, Korea 8.80–18,5Naples' harbour, southern Italy 9–31 774(Hadhramout coast, Gulf of Aden, Yemen 2.2–604.4

out coastal area, Gulf of Aden can be considered low to moderatepolluted with PAHs (2.2–604 ng g−1).

3.4. Toxicity assessment

Long et al. (1995) conducted an extensive review of articles thatprovide both concentrations of contaminants in sediments andobserved biological effects. They therefore derive consensus valuesconsidering data for all of the studies reviewed. Sediment concentra-tions shown by the studies to cause biological effects, and judge validwere ranked from low to high. A 10th and 50th percentile were thendetermined. Those were designated effects range low (ER-L) andeffects range median (ER-M). ERM and ERL values are useful inaddressing sediment quality issues and provide qualitative guidelines

References

(∑15 PAHs) Botello et al. (1991)∑18 PAHs) Wade et al. (1995)900,000 (∑13 PAHs) Readman et al. (1996)0 (∑14 PAHs) Baumard et al. (1998)5 (∑28 PAHs) Gogou et al. (2000)0 (∑17 PAHs) Nishigima et al. (2001)000 (∑14 PAHs) Tolun et al. (2001)16 PAH) Readman et al., 2002

0 (∑15 PAHs) Viguri et al. (2002)(∑17 PAHs) Readman et al. (2002)(∑17 PAHs) Readman et al. (2002)∑17 PAHs) Readman et al. (2002)(∑43 PAHs) Mostafa et al. (2003)

8 (∑27 PAHs) Fang et al. (2003)16 PAHs) Doong and Lin (2004)

(∑46 PAHs) Tolosa et al. (2004)46 PAHs) Tolosa et al. (2004)(∑46 PAHs) Tolosa et al. (2004),000(∑16 PAHs) Shi et al. (2005)19 PAHs) Tolosa et al. (2005)

(∑19 PAHs) Tolosa et al. (2005)∑19 PAHs) Tolosa et al. (2005)19 PAHs) Tolosa et al. (2005)

3 (∑15 PAHs) El Nemer et al. (2006)82((∑13 PAHs) Ünlü and Alpar (2006)(∑18 PAHs) Liu et al. (2007)754 (∑16 PAHs) Qiao et al. (2006)5 (∑18 PAHs) Guo et al. (2007)00 (∑16 PAHs) Yim et al. (2007)∑16 PAHs) Sprovieri et al. (2007)(∑46 PAHs) Present study

Table 4ERL and ERM values for some PAHs in surface sediments of Hadhramout costal area,Gulf of Aden (ng g−1).

Compound ERL ERM Present study

Max Min

Naphthalene 160 2100 7.66 0.00Acenaphthylene 44 640 0.87 0.00Acenaphthene 16 500 0.44 0.00Fluorene 19 540 1.30 0.00Dibenzothiophene 190 1200 2.02 0.00Phenanthrene 240 1500 15.47 0.24Anthracene 85 1100 10.06 0.00Fluoranthene 600 5100 43.33 0.00Pyrene 665 2600 39.71 0.00Benzo[a]anthracene 260 1600 9.16 0.00Chrysene 380 2800 12.84 0.00Benzo[a]pyrene 430 2800 14.75 0.00Indeno[123-cd]pyrene 240 950 9.81 0.00Dibenzo[ah]anthracene 63 260 7.62 0.00Benzo[ghi]perylene 85 330 12.03 0.002-Methylnaphthalene 70 670 5.17 0.001-Methylnaphthalene 85 800 9.65 0.00C2-naphthalenes 150 1450 14.15 0.00C1-phenanthrenes 170 2000 7.82 0.00C2-phenanthrenes 200 2500 21.68 0.00C1-dibenzothiophenes 85 600 32.42 0.00

7A.R. Mostafa et al. / Journal of Marine Systems 78 (2009) 1–8

onwhat needs to be done to effectively protect the aquatic organisms.The concentrations of most organic contaminants detected are belowthe concentration levels that are believed to evoke toxic responses inmarine benthic organisms. The ER-L and ER-M values for some PAHcompounds are listed in (Table 4). The high value recorded ofinvestigated pollutants were 43.3 and 39.7 ng g−1 for Fluorantheneand pyrene respectively. Thus concentrations of PAHs found in thisstudy are not expected to be a threat to benthic marine organismsalong the Hadhramout coastal region.

4. Conclusions

This study has provided data on the levels of PAHs in the surfacesediments of Hadhramout coastal sediments Gulf of Aden. PAHscontamination is closely related to petroleum spills, shipping, sewageinput, runoff of intermittent stream and industrial activities. Finger-printing analysis indicates that PAHs in the sediment were mostlypetrogenic in origin likely due to shipping activities, whereas pyrogenicorigin was found for PAHs in some sediment probably due to the highcombustion inputs and urban runoffs from urbanized areas. Compar-ison of the concentration range with a worldwide survey of sedimen-tary PAH concentrations ranked PAH contamination in Hadhramoutcoastal sediments as low to moderate pollution. This may be related tothe high (%) of sand in these sediments. Adverse effect to benthiccommunities is not expected at the levels of PAHs contaminationobserved from harbour and industrial area. Data on the PAHs found inthis survey can be used as baseline reference concentration for futurePAHs monitoring programs (e.g. in the event of an oil spill).

Acknowledgements

We are grateful to Lisa Reichert, Geochemical and EnvironmentalResearch Group (GERG), for their technical assistance in analysis.Constructive commentsof the co-editor,W. Fennel, andotheranonymousreviewers are highly appreciated.

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