Origin of Polycyclic Aromatic Hydrocarbons (PAHs) in Coastal Marine Sediments: Case Studies in Cotonou (Benin) and Aquitaine (France) Areas

PII: S0025-326X(99)00200-3

Marine Pollution Bulletin Vol. 40, No. 5, pp. 387±396, 2000 Ó 2000 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0025-326X/00 $ - see front matter

Origin of Polycyclic Aromatic Hydrocarbons (PAHs) in Coastal Marine Sediments: Case Studies in Cotonou (Benin) and Aquitaine (France) Areas H. H. SOCLO *, PH. GARRIGUESà and M. EWALDà  Unit e de Recherche en Ecotoxicologie et Etude de Qualit e, Coll ege Polytechnique Universitaire/Universit e Nationale du B enin 01 BP 2009, Cotonou (Benin), France àESA 5472 CNRS, Universit e de bordeaux I, 351 cours de la Lib eration, 33405 Talence Cedex, France Polycyclic Aromatic Hydrocarbons (PAHs) were identi®ed and quanti®ed in recent sediments of the Cotonou coastal zones (Benin) in the total concentration range 25± 1450 ng gÿ1 , while the Aquitaine sediment samples (France) exhibited total PAH concentrations in the range 4±855 ng gÿ1 . The highest contents of PAHs were found in the harbours, as well in Cotonou as in the Aquitaine region, with the maximum values in the Cotonou harbour. However, the PAH concentrations were comparable with those of slightly contaminated zones. Good correlations observed between a certain number of pairs of isomer PAH concentrations allowed to identify six origin molecular indices that were used to identify the PAH contamination sources in the studied sampling stations: Phe/ An, Flt/Py, Chry/BaA, LMW/HMW, Per/+(PAH), and Per/+(penta-aromatics). In general, the Cotonou lagoon sampling sites were contaminated mainly by petrogenic PAHs, due to petroleum trade at individual scale along the lagoon, and also waste oils from mechanics shops; the Aquitaine samples were polluted by pyrolytic origin PAHs. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed in the harbours due to petroleum products deliveries and fuel combustion emissions from the ships staying alongside the quays. Diagenetic origin of perylene was con®rmed in this study, but its possible formation by combustion of organic matter was also considered because of the relatively higher concentrations of this PAH in the harbours of Cotonou and of Aquitaine region sediment samples. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: PAH; sediments; origin indices; Lagoon of Cotonou; Estuary of Gironde; Arcachon Bay. * Corresponding author. Fax: +229-36-01-99. E-mail address: [email protected]

Introduction Many studies have been made on polycyclic aromatic compounds (PACs) in the di€erent compartments of the environment, owing to their carcinogenic and mutagenic activities in living and/or human beings (Lehr and Jerina, 1977). They have been intensively studied for their geochemical interest as markers in identifying sedimentary deposits origin and evolution in the aquatic environment (Grimmer and B ohnke, 1975; Heit et al., 1981). Polycyclic aromatic hydrocarbons (PAHs) form a widespread class of environmental chemical pollutants. They can be introduced in the environment by various processes (Ne€, 1979; McElroy et al., 1989): incomplete combustion at higher temperatures of recent and fossil organic matter (pyrolytic origin), slow maturation of organic matter under the geochemical gradient conditions (petrogenic origin) and short-term diagenetic degradation of biogenic precursors (diagenesis). Direct PAH biosynthesis by organisms such as bacteria, fungus, and algae has not yet been clari®ed (Parlanti, 1990). Most PAH inputs in the environment are linked to the anthropogenic activity that is generally considered to be the major source of these compounds (e.g., wastes from industrialized and urbanized areas, o€-shore petroleum hydrocarbons production or petroleum transportation). Each source (pyrolytic, petroleum and diagenetic hydrocarbons) gives rise to characteristic PAH pattern, and it is therefore possible to get access to the processes that generate the compounds. Kinetic and/or thermodynamic criteria, and the nature of organic matter govern the PAH distribution in the environment. PAHs have di€erent distribution patterns according to their production sources. Diculties exist in identifying their origins in sedimentary medium, owing to the possible co-existence of several sources 387

Marine Pollution Bulletin

(various pyrolytic sources, petrogenic contamination, early diagenesis). In addition, physical-chemical properties of some PAH, like chemical reactivity (photooxidation, oxidation), can contribute to modify the original distribution pattern of the emission sources (Butler and Crossley, 1981). In marine ecosystems, PAHs can undergo degradation by photooxidation in the super®cial water layer(Mill et al., 1981), and by microbial activities into the sediments (Cerniglia and Heitkamp, 1989). However, PAH ubiquity in the sediments indicate that accumulation phenomena dominate degradation processes in sedimentary matrices (Readman et al., 1984; Smith and Levy, 1990), so, some PAHs could exhibit comparable evolution kinetics. Molecular indices based on PAH physical-chemical behaviour covariability were developed to assess the various origins of these pollutants (Soclo, 1986; Baumard et al., 1998). With simultaneous association of various molecular indices, it is possible to determine which process generated such hydrocarbons in the studied matrices (Lake et al., 1979; Ne€, 1979; Budzinski et al., 1997). The present study is focused on sediment samples collected from nearshore waters and lagoon of Cotonou (Benin), and also from the Estuary of Gironde and Arcachon Bay (France). The di€erent climatic regions, added to their di€erent levels of industrialization, would be perhaps interesting criteria that would in¯uence the PAH distributions in the aquatic environment. The interest of this work is thus to identify and quantify PAHs recommended by US-Environmental Protection Agency (US-EPA) as priority pollutants to be monitored in the framework of the environmental quality control. The lowest molecular weight PAHs such as naphthalene, acenaphthene, acenaphthylene, and ¯uorene were not taken account in this study, because of their higher volatility resulting in losses during the experiments. Two other non-US-EPA list PAHs, such as Benzo(e)pyrene and perylene, were also studied, because of additional information they would provide on PAH origins; perylene was usually considered as terrestrial origin marker of organic matter in the sediments (Louda and Baker, 1984; Venkatsen, 1988; Parlanti, 1990).

Experimental Procedure Sampling The samples were collected in Benin, during the rainy seasons (September) when rivers and urban channels discharged great quantities of terrestrial and run-o€ materials in the coastal aquatic ecosystems (lagoon of Cotonou and sea). The sampling sites in the lagoon and in the harbour of Cotonou are indicated in Fig. 1(a) and described in Table 1. In the Aquitaine Region in France, two groups of sediments can be distinguished: Estuary of Gironde (since the Garonne river until the estuary mouth in 388

Verdon), and the Arcachon Basin samples. These ecosystems are presented in Fig. 1 and Table 1. Super®cial sediments samples (0±2 cm deep) were collected with a Schipeck grab, then wrapped in aluminium foil, and transferred in an ice box to the laboratory where they were frozen at ÿ20°C. Sample preparation for chemical analyses The freeze-dried sediments were extracted as reported previously (Monin et al., 1978; Soclo et al., 1986). Prior to extraction, the internal standards, namely phenanthrene-d10 and benzo(a)pyrene-d12 , were added to the freeze-dried sediments. The extraction conditions were: one mechanical stirring extraction step during 45 mn with 100 ml chloroform/toluene mixture (2:1 by volumes) heated at 45°C. Activated copper was added in the extraction vessel to reduce or eliminate the elemental sulphur content from the extract. The sample was ®ltered and the total organic extract reduced to about 1 ml using a rotary evaporator, and then puri®ed by liquid chromatography on ¯orisil microcolumn (Sep-Pak, Waters-Millipore) to eliminate polar compounds and resins. The puri®ed fraction was reduced under nitrogen gas stream to a ®nal volume of 1 ml for HPLC-Fluorimetry analyses. HPLC-spectro¯uorimetry analyses The hydrocarbons fraction was analysed by high performance liquid chromatography (HPLC) coupled to spectro¯uorimetry. The column used was an octadecyl (C18) (L ˆ 25 cm; / ˆ 4:6 cm; Vydak 201 TP, 5 lm). Isocratic elution was executed with acetonitrile-water mixture (85:15 by volumes) by means of a pump (Constametric III; LDC Milton Roy). The PAH detection was made on a spectro¯uorimeter programming 14 couples of wavelength (excitation/ emission; pathway: 10 nm) according to the compounds' retention times (spectro¯uorimeter LS-5, Perkin± Elmer). They were quanti®ed relative to perdeutered PAHs (Quilliam et al., 1994; Baumard and Budzinski, 1997) added to the sediments matrix prior to the extraction. Phenanthrene-d10 was used for the lower molecular weight PAHs, and benzo(a)pyrene-d12 for the higher molecular weight ones. The response factors of the di€erent aromatic compounds were measured by injecting a standard reference solution of the 18 PAHs spiked with the same internal standards. The studied parent PAHs ranged from the di-aromatics to the hexa-aromatics. Because of their relative higher volatility, naphthalene, acenaphthene, acenaphthylene and ¯uorene were not quanti®ed. Those that were measured ranged from the tri-aromatics (phenanthrene, anthracene) to the hexa-aromatics (1, 2, 3, c-d-indenopyrene). The abbreviations used for the PAHs are: phenanthrene (Phe); anthracene (An); ¯uoranthene (Flt); pyrene (Py); chrysene

Volume 40/Number 5/May 2000

Fig. 1 (a) Location of the sampling sites in the Cotonou nearshore and lagoon. (b) Location of the sampling sites in the Gironde estuary and in the Arcachon bay.

(Chry); Benzo(a)anthracene (BaA); benzo(e)pyrene (BeP); benzo(b)¯uoranthene (BbF); perylene (Per); benzo(k)¯uoranthene (BkF); Benzo(a)pyrene (BaP); dibenzo(a,h) anthracene (DBA); and 1, 2, 3, c-d indenopyrene (IPy). Total PAH is the sum of the precited 14 parent PAH concentrations, given in ng gÿ1 dry weight.

The detection limit of each PAH is an average of about 3 pg for the sediment samples. The protocol was validated by the use of material which has been used in an intercalibration exercise (Vo Dinh and Martinez, 1981). The recoveries of PAHs in a certi®ed Solvent Re®ned Coal (SRC II) averaged >85% with a variation coecient <10%. 389

Marine Pollution Bulletin TABLE 1 Description of the sampling sites. Country Benin Benin Benin Benin Benin Benin France France France France France France France France

Sampling sites

Sites description

Harbour basin (IB ) Trading boats accosting in the Gulf of Guinea Sitty mud near the quay Harbour basin (IIB ) Petroleum boats accosting, near the quay Sitty mud Harbour basin (IIIB ) Exit of the harbour Muddy sand Mouth of the Entrance the channel near the stones closure Mud + shell debris lagoon (IVB ) (urbanised area) Nokoue lake (VB ) Nokoue entrance from the channel Mud + plant debris Rural channel linking Cotonou and Fine sand+shell Channel of Totche Porto-Novo lagoons, remote to urban area debris (VIB ) Soulac (IF) Continental shelf near the coast Sandy Cordouan (IIF) At the mouth of the Estuary of Gironde Sandy (grass sand with shell debris) Royan (IIIF) Inside the harbour Sandy Channel of the Middle of the channel of the Estuary of Sandy Estuary (IVF ) Gironde (in front of Verdon) Verdon (VF) Near the old tidemeter, Petroleum pipeline Sandy, muddy silt termi-Nal, tanks inloading area Verdon (VIF ) Sheckle of Verdon Muddy Garonne±Bordeaux Garonne River bank Muddy cream (VIIF ) Arcachon Bay Important oyster farming and tourism Sandy (VIIIF ) activity zone in summer

Chemicals, reagents and samples The HPLC grade pentane, acetonitrile and methanol were puri®ed by distillation, and tested by ambient temperature ¯uorescence (MPF-44, Perkin±Elmer). The water was puri®ed by elution through an anion exchange cartridge (demino 1100, Sadon, TEE, Bordeaux, France). The copper (40 mesh, 99.5% purity, Aldrich, Strasbourg) was activated by hydrochloric acid (1N) and then washed with water, acetone and dichloromethane. The compounds used as internal standards were perdeutered phenanthrene and benzo(a)pyrene, supplied by Cambridge Isotope Laboratories, Cambridge (Great Britain). The Standard Reference Material Aromatic Hydrocarbons were supplied by National Institute of Standards and Technology (NIST, Gaithersburg, MD, USA) as well as SCR II (coal liquid fuel).

Results and Discussion Sediment pollution levels There are no previously published data on organic pollutant contents such as individual PAHs on the coastal water ecosystems in Benin. Tables 2(a) and (b), Fig. 2(a)±(c) exhibit quantitative results obtained, respectively, in Cotonou lagoon and nearshore environment in one side, and in the Estuary of Gironde and Arcachon Bay in the other one. A wide range of total PAH concentrations was observed from less than 4 ng gÿ1 to more than 1400 ng gÿ1 (dry weight). The greatest pollution levels were observed for sediments sampled in stations IIB and VIF showing the harbours of Cotonou (1410 ng gÿ1 ) and Verdon (853 ng gÿ1 ) as being the most contaminated by PAHs among all the studied sites. What was surprising was that, the 390

Sample grain facies

Latitude (North) 0

6° 15 32

00

Longitude (East) 2° 260

6° 160 0900 6° 150 5400 6° 170 0700

2° 260 3400 2° 270 2400 2° 260 2400

6° 200 5800 6° 250 1800

2° 260 2° 350 3600

45° 300 1200 45° 350

1° 090 1200 1° 060

45° 360 0900 45° 33' 4000

2° 020 3000 1° 000 3000

45° 310

1° 040

sediments collected inside Cotonou harbour (1205±1411 ng gÿ1 ) were found to be polluted to a higher extent than those sampled in the Bordeaux and Verdon harbours (respectiveley 491 and 853 ng gÿ1 ), in spite of many shipping activities usually registered in the latter sampling stations. One possible explanation would be probably the abundant release of petroleum residues in the Cotonou harbour by the ships, in de®ance of the existing regulations; beaches of the Gulf of Guinea contain quantities of tarballs resulting from bilge water discharged by commercial ships (WACAF II, 1988). The contamination levels in Cotonou and Bordeaux harbours appeared however lower than those found by Baumard et al. (1998) in Barcelona (1700 ng gÿ1 ) and Port Vendres (6900 ng gÿ1 ) harbours, in Spain and France, respectively. The sampling sites were also less contaminated than Mediterranean coastal sediments characterized by PAH concentration values in the range 100±13 000 ng gÿ1 (Raoux, 1991; Raoux and Garrigues, 1993). These values were comparable with PAHs levels found by Baumard et al. (1998), for French (35±1000 ng gÿ1 ) and Spanish (1±850 ng gÿ1 ) coasts. Globally, these quantitative results showed relatively low concentrations as well in the Estuary of Gironde as in the Cotonou aquatic ecosystems; these PAH levels in the studied sites, closed to the mean values (1400 ng gÿ1 ) found by Budzinski et al. (1997) in the Gironde estuary, were similar to the slightly contaminated zones. Except in harbours, all the coastal sediment samples were contaminated in the range 25±120 ng gÿ1 . Mean PAH concentrations were respectively 94 ng gÿ1 (Cotonou) and 8.4 ng gÿ1 (estuary of Gironde). The same tendency in increasing of the PAH contents was observed also for the lagoon and estuarine ecosystems. The higher PAH concentrations found in the lagoon of

Volume 40/Number 5/May 2000 TABLE 2A Concentrations of individual parent Polycyclic Aromatic Hydrocarbons (PAHs) in sediments collected in the lagoon and in coastal waters in Cotonou±Benin (ng gÿ1 ). Stations

Harbour basin (IB) Harbour basin(IIB) Harbour basin (IIIB) Mouth of the Lagoon (IVB) Nokoue Lake (VB) Channel of Totche (VIB) a

PAHs Phe

An

Flt

Py

BaA

Chry

BeP

BbF

Per

BkF

BaP

DBA

Bper

Ipy

 PAH

36 66 6 7 15 5

5 9 0.1 0.4 1 1

72 224 4 10 21 7

80 163 4 11 29 15

154 160 n.q.a 1 5 2

175 230 n.q. 9 17 6

313 112 n.q. n.q. n.q. n.q.

119 92 2 7 7 4

16 34 1 3 4 29

40 68 1 5 4 3

56 124 1 7 4 4

24 9 1 4 4 2

54 56 4 6 6 2

61 64 1 14 n.q. n.q.

1205 1411 25.1 84.4 117 80

n.q.: not quanti®ed. TABLE 2B

Concentrations of individual parent Polycyclic Aromatic Hydrocarbons (PAHs) in sediments collected in the Estuary of Gironde and in the Arcachon Bay in France (ng gÿ1 ). PAHs Stations

Phe

An

Flt

Py

BaA

Chry

BeP

BbF

Soulac (IF) Cordouan (IIF) Royan (IIIF) Channel of Estuary (IVF) Verdon (VF) Verdon (VIF) Garonne±Bordeaux (VIIF) Arcachon Bay (VIIIF)

0.5 1 1 1 18 74 33 12

0.1 0.1 0.1 0.1 8 18 10 3

1 0.5 1.5 1 43 100 63 51

1 1 1.5 1 42 102 46 43

0.3 0.5 1.4 1.5 32 68 24 26

0.2 1.5 1.5 5 23 45 19 23

n.q.a 2 1 n.q. 37 103 20 35

0.2 0.1 1.5 1 31 79 36 17

a

Per

BkF

n.q. 0.1 <0.1 <0.1 0.5 1 2 0.5 45 17 52 24 101 21 7 9

BaP 0.1 n.q. 1 0.5 27 52 35 16

DBA Bper n.q. n.q. 0.1 0.5 2 12 9 3

n.q. n.q. 1 1 21 73 28 25

Ipy n.q. n.q. 1.5 n.q. 25 51 46 22

PAH 3.5 6.7 14.6 15.1 371 853 491 293

n.q.: not quanti®ed.

Cotonou compared with those of the Estuary of Gironde, by a factor of 10 relative to Aquitaine values, could be explained by the geomorphology of the lagoon system which receives untreated wastes. The PAH higher concentrations in the lagoon of Cotonou were found at the station situated near the mouth. This sampling station (IIIB ) was chosen at the upperstream side of the site built in 1978 to regulate the water circulation from the lake and rivers. Another high value of PAH was found in the small channel of Totche; a rural site remote to any urban activities. This 5 km channel links the two lagoon ecosystems of Cotonou and Porto-Novo. Identi®cation of the PAH contamination sources The aromatic compound distributions di€er according to the production sources, and on the chemical composition and temperature combustion of the organic matter (Ne€, 1979). The ®ngerprints of PAHs from pyrolytic or petrogenic origin may be used to di€erentiate these origins by using molecular indices based on ratios of selected PAH concentrations (Colombo et al., 1989). One diculty in identifying PAH origins, is the possible coexistence of many contamination sources, and the transformation processes that PAHs can undergo before deposition in the analysed sediments (Butler and Crossley, 1981). Nevertheless, some compounds could

exhibit comparable evolution kinetics that could be used to identify the origin of organic matter in the environment. Possible covariability between PAH concentrations The PAHs whose concentrations are susceptible of covarying in the environment were identi®ed in this study on the basis of the correlation factor values (Tables 3(a) and (b)) (Bourbon et al., 1986; Sletter et al., 1986). This statistical approach is based on the fact that each pollution source produces a characteristic PAH pattern; so, the correlation factors between the sediment concentrations of all the individual PAHs can give an idea whether they all originate from the same source or not. From the calculated correlation factors, a certain number of observations were made. One preliminary remark was that the correlation coecients calculated for the Cotonou samples appeared to be higher (mean value of r2 ˆ 0.90) than those obtained for the sediment samples collected in the Aquitaine region (r2 ˆ 0.60). The low PAH correlation in this latter case would suggest fewer contamination sources in the Cotonou lagoon and in its surrounding zones, probably because of the lower industrialization level in Cotonou. In Benin, PAHs would originate mainly from petrogenic and/or pyrolytic sources, whereas in the Aquitaine region, interferences of many PAH sources would be responsible for the lowest correlation factors. 391

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ferent ecosystems suggests that perylene originates from terrestrial organic matter; the other PAHs would be generated from pyrolytic or petrogenic/diagenetic processes (Venkatesan, 1988; Parlanti, 1990). Five signi®cant PAH ratios were drawn from the correlation factors Tables and were calculated for the studied samples: Phe/An, Flt/Py, Chry/BaA, LMW/ HMW …i:e: Phe ‡ An ‡ Py ‡ Flt=BaA‡ Chry ‡ BbF‡ BkF ‡ BaP ‡ BeP ‡ Per‡ DBA ‡ Bper ‡ Ipy† and Per/ S(Penta-aromatic isomers). Penta-aromatic isomers are recognized as being PAHs with six rings, such as Per, BeP, BaP, DBA, BbF and BkF. In recent studies, these above-calculated indices were used by other authors to assess and determine with accuracy the origin of the PAHs from various environments (Sicre et al., 1987; Budzinski et al., 1997; Benlahcen et al., 1997; Baumard, 1997; Baumard et al., 1998).

Fig. 2 (a) Plot of total PAH levels in the di€erent sediment sampling sites (in the studied Cotonou and Aquitaine coastal water ecosystems). (b) Plot of total PAH levels in the Cotonou sampling sites. (c) Plot of total PAH levels in the Aquitaine sampling sites.

In addition, a lack of correlation or negative correlation was noticed between perylene and the other PAHs (r2 ˆ 0.11±0.69). The perylene behaviour in the two dif392

Sources of PAH contamination in the studied stations In fact, phenanthrene and anthracene are two structural isomers. Because of their di€erent physico-chemical properties, they could behave di€erently in the environment and could lead to di€erent values for their Phe/An ratio that would give useful information on the PAH origin (Gschweng and Hites, 1981). Phenanthrene is more thermodynamically stable than anthracene, so, Phe/An ratio is observed to be very high in PAH petrogenic pollution, but lower in pyrolytic contamination cases. Good correlations were observed between the two isomeric PAHs (r2 ˆ 0.98 for the Cotonou samples; r2 ˆ 0.79 for the Aquitaine ones). This slight di€erence between the two series of sediment samples concerning the phenanthrene and anthracene correlation could be explained by their tendency to degrade. In the same way, ¯uoranthene and pyrene were often associated during natural matrices analyses and were considered as typical pyrogenic products derived from high-temperature condensation of lower molecular weight aromatic compounds. The excellent coecient factor (r2 ˆ 0.98 for the both Cotonou and Aquitaine samples) observed between these two PAHs indicates probably their similar behaviour independently of the sediment sampling sites. Chrysene and benzo(a)anthracene are derived from processes of organic matter combustion at high temperature, with values of Chry/BaA ratio lower than 1 (Parlanti, 1990). In contrast, low maturation of organic matter during burial in the sedimentary matrix could lead to an inversion of this tendency: Chry/BaA ˆ 1 (Parlanti, 1990). It has been shown that chrysenic derivatives are more stable than benzanthracenic ones, because of the possibility of the latter ones to convert to chrysenic compounds. To estimate the origin of the pollution in the Cotonou and Aquitaine sediment samples, the Low/High ratio (sum of the low molecular weight PAH concentrations versus sum of higher molecular weight PAH concen-

Volume 40/Number 5/May 2000 TABLE 3A Correlation factors between the PAH concentrations in the sediments (Benin samples). PAHs

PAHs

Phe

An

Flt

Py

BaA

Chry

BeP

BbF

Per

BkF

BaP

DBA

BPer

Ipy

1.00

0.99 1.00

0.98 0.97 1.00

0.99 0.99 0.99 1.00

0.91 0.94 0.82 0.89 1.00

0.96 0.98 0.90 0.95 0.96 1.00

NSa NS NS Ns NS NS 1.00

0.84 0.88 0.73 0.79 0.98 0.94 1.00 1.00

0.63 0.68 0.68 0.69 0.52 0.56 NS 0.50 1.00

0.99 0.99 0.96 0.99 0.94 0.98 NS 0.88 0.67 1.00

0.99 0.99 0.99 0.99 0.90 0.96 NS 0.82 0.69 0.99 1.00

0.55 0.60 0.38 0.51 0.79 0.67 NS 0.91 0.25 0.61 0.48 1.00

0.92 0.94 0.84 0.90 0.99 0.98 NS 0.98 0.55 0.95 0.90 0.82 1.00

0.91 0.94 0.81 0.90 0.99 0.98 NS 0.97 0.89 0.94 0.88 0.77 0.99 1.00

a

Phe An Flt Py BaA Chry BeP BbF Per BkF BaP DBA BPer Ipy

NS: Not Signi®cant.

TABLE 3B Correlation factors between the PAH concentrations in the sediments (Gironde samples). PAHs

PAHs

Phe

An

Flt

Py

BaA

Chry

BeP

BbF

Per

BkF

BaP

DBA

BPer

IPy

1.00

0.79 1.00

0.97 0.63 1.00

0.97 0.49 0.98 1.00

0.90 0.80 0.83 0.90 1.00

0.87 0.35 0.92 0.92 0.71 1.00

0.90 0.49 0.94 0.97 0.94 0.98 1.00

0.98 0.87 0.91 0.93 0.95 0.75 0.85 1.00

0.40 0.51 0.33 0.21 0.07 0.16 0.11 0.37 1.00

0.87 0.53 0.90 0.87 0.65 0.91 0.87 0.80 0.55 1.00

0.97 0.70 0.96 0.95 0.81 0.89 0.91 0.93 0.50 0.96 1.00

0.83 0.52 0.96 0.60 0.67 0.92 0.89 0.81 0.48 0.54 0.95 1.00

0.90 0.85 0.82 0.86 0.96 0.60 0.75 0.94 0.14 0.56 0.76 0.65 1.00

0.93 0.76 0.92 0.85 0.69 0.74 0.75 0.88 0.68 0.89 0.94 0.93 0.74 1.00

trations) was the ®rst origin index used in this study (Fig. 3(a) and (b)). The choice of this origin index was founded on the fact that the petrogenic contamination was characterized by the predominance of the lower molecular weight PAHs (tri- and tetra-aromatics) (Ne€, 1979; Wise et al., 1988; Berner et al., 1990), while the higher molecular weight PAHs dominated in the pyrolytic PAH contamination distribution (Muel and Saguem, 1985). Examination of Fig. 3(a) and (b) shows for the majority of the samples, values of the ratio LMW/HMW lower than 1 (values between 0.19 and 0.63), indicating pyrolytic origin pollution. Only, sediment samples from sites IIIB (situated near the coast outside the harbour basin), IVB (entrance of Nokoue lake) and from Soulac (near the coast in the open sea, but not far from the Gironde estuary), revealed LMW/HMW ratio values higher than 1 (1.3 and 2.9). As lower molecular weight PAHs (like phenanthrene, anthracene, pyrene) dominate the higher molecular weight PAHs during low-

Phe An Flt Py BaA Chry BeP BbF Per BkF BaP DBA BPer IPy

temperature maturation of organic matter (Ne€, 1979; Garrigues et al., 1993), these ratios indicate that these three stations were contaminated mainly by petrogenic PAHs. LMW/HMW values equal to 2.9 in Soulac sample seemed to indicate that the petrogenic pollution source was greater in this sampling site than in the two other ones. It was noticeable that petrogenic PAH pollution was greater in Soulac (LMW HMW ˆ 2.9) than in the two other samples such as IIIB and VB in Cotonou. For the other sites, LW/HW ratio values were in the ranges 0.2± 0.5 (for Cotonou). In order to better characterize the PAH distribution, the molecular origin indices Phe/An (Phenanthrene concentration versus anthracene concentration) were plotted against Flt/Py (Fluoranthene concentration versus pyrene concentration) (Fig. 4). Following the approach adopted by Baumard et al. (1998) two Standard Reference Materials (SRM) were used as PAH origin indicators in the sediments. Coal 393

Marine Pollution Bulletin

Fig. 4 (a) Plot of the isomeric ratios Phe/An against Flt/Py for the studied samples (Cotonou). (b) Plot of the isomeric ratios Phe/ An against Flt/Py for the studied samples (Aquitaine). Fig. 3 (a) Plot of sum of lower molecular weight PAH concentrations versus sum of higher molecular weight PAH concentrations (for Cotonou samples). (b) Plot of sum of lower molecular weight PAH concentrations versus sum of higher molecular weight PAH concentrations (for Aquitaine samples).

Tar SRM 1579 is characteristic of pyrolytic PAH origin, and Shale Oil SRM 1580 of petrogenic PAH contamination. Their respective Phe/An and Flt/Py ratio values were introduced in the preceding plot (Fig. 4). The majority of Cotonou samples grouped in the Flt=Py < 1 zone including shale oil SRM 1580 point (FltPy ˆ 0.75; Phe/An ˆ 58). On the contrary, Aquitaine samples grouped around the point of coal tar SRM 1579 (Flt/Py ˆ 1.37; Phe/An ˆ 2.60). Considering ®rst the individual values of the Phe/An and Flt/Py ratios, most of the sites were characterized by Phe/An values < 10 and Flt/Py values  1, which is characteristic of pyrolytic and petrogenic contaminations with strong pyrolytic input. The plot of Phe/An against Flt/Py, the stations IIB (Cotonou harbour), VIIF (Bordeaux harbour) and VIIIF (Arcachon bay) shows pyrolytic PAH contamination in these sampling sites. This would originate from fossil fuel combustion particulates emitted by commercial 394

ships. Arcachon bay has intense tourist activities during the summer. The pyrolytic contamination of the bay could be attributed to pleasure boat combustion particles emission. The pyrolytic PAH inputs in Arcachon bay are con®rmed by the Chry/BaA ratio values which are lower than 1. In Aquitaine, many discrimination problems exist because their origin indices are at the border between pyrolytic and petrogenic zones …Flt=Py ˆ 1 or Phe= An ˆ 10†. In Cotonou, IB , IVB , VB , and VIB were characterized by Flt/Py values lower than 1 (0.5ÿ1), and Chry/BaA higher than 1. These sampling sites appeared to be contaminated by petrogenic PAH. However, in spite of the diculty in identifying the PAH origin in the point IIIB because of the Chry/BaA value equal to zero, the very high value of Phe/An ratio …Phe=An ˆ 60† indicated petrogenic pollution of this site. The high predominance of thermodynamically stable phenanthrene on its isomer anthracene is characteristic of contamination by petroleum products (Baumard, 1997). The position of the site IIIB in the graph Phe/An versus Flt/Py was also close to that of shale oil SRM 1580. Position of station IIB close to coal

Volume 40/Number 5/May 2000

tar SRM 1579 point in the graph of the Phe=An ˆ f (Flt/Py) indicated pyrolytic PAH pollution. On the contrary, the majority of the Aquitaine samples (IF , VF , VIF , VIIF , and VIIIF ) lay around the coal tar SRM 1579, indicating pollution by pyrolytic PAH origin. Discrimination was made for the stations IIF …Cordouan: Flt=Py ˆ 0:5 and Phe=An ˆ 10†, IIIF (Royan), and IVF …Flt=Py ˆ 1 and Phe=An ˆ 10† using Chry/BaA ratio as origin indicator. The Chry/BaA value > 1 for this station, showing petrogenic PAH contamination, with probably a slightly pyrolytic PAH contamination, due perhaps to the shipping trac in the harbour of Verdon and in its surrounding zones.

Perylene origin Perylene concentrations were in the ranges 1±35 ng gÿ1 for the Cotonou stations and less than 0.1±100 ng gÿ1 for the Aquitaine sediment samples. But the highest concentrations were found in the harbours: in the range 16±34 ng gÿ1 for Cotonou, and 37±103 ng gÿ1 for the Aquitaine harbours where the maximum was detected in Bordeaux (101 ng gÿ1 ) and Verdon (103 ng gÿ1 ) harbours. In order to access with accuracy the perylene origin in recent samples, the relative concentrations of perylene (concentration of perylene versus sum of penta-aromatic concentrations) were plotted against the sampling stations (Fig. 5(a) and (b)). The plot obtained presented the same trend with that of perylene concentration versus sum of PAH concentrations. The relative perylene concentrations of the majority of the sampling stations were in the range 1±6%. Exception was noticed for the sites IB , VB and VIIF , where perylene was relatively very abundant (36.25% for the Totche channel station, 20.57% for the garonne station, and 12.13% for Verdon). As indicated above, the channel of Totche links the two lagoon ecosystems of Cotonou and Porto-Novo, and receives a good part of material deposition from the Oueme river. The station VF was situated the mouth of the Gironde estuary while site VIIF was in the Garonne river. These higher relative concentrations could result from terrigenous precursors whose degradation could lead to the formation of perylene. Thus perylene presence in these three speci®c stations enriched by rivers discharges could be related to a diagenetic origin (Venkatsen, 1988). We thank the technical personal of the ``Bureau dÕEtudes de la Dircetion Generale du Port Autonome de Cotonou'' and particularly Mr Celestin Noumon, for their technical help in sediment samplings in Cotonou area. CNRS is knowledged for research vessel C^ ote dÕAquitaine-Region Aquitaine and for ®nancial support.

Fig. 5 (a) Plot of relative concentration of perylene (Per/Penta-aromatics and Per/Total PAH) against the Cotonou sampling sites. (b) Plot of relative concentration of perylene (Per/Pentaaromatics and Per/Total PAH) against the Cotonou sampling sites.

Baumard, P. (1997) Biochimie des composes aromatiques dans lÕenvironnement marin. PhD thesis Nr. 1788, University Bordeaux I, Bordeaux, France. Baumard, P. and Budzinski, H. (1997) Internal standard quanti®cation method and gas chromatograph±mass spectrometer (GC±MS): a reliable tool for polycyclic aromatic hydrocarbon (PAH) quanti®cation in natural matrices. Analysis 25, 246±252. Baumard, P., Budzinski, H., Michon, Q., Garrigues, P., Burgeot, T. and Bellocq, J. (1998) Origin and bioavailability of PAHs in the Mediterranean sea from mussel and sediment records. Estuarine, Coastal and Shelf Science 47, 77±90. Benlahcen, K. T., Chaoui, A., Budzinski, H., Bellocq, J. and Garrigues, P. (1997) Distribution and sources of polycyclic aromatic hydrocarbons in some mediterranean coastal sediments. Marine Pollution Bulletin 34, 298±316. Berner, B. A. Jr., Bryner N. P., Wise S. A., Mulholland G. H., Lao, R. C. and Fingas, M. F. (1990) Polycyclic aromatic hydrocarbon emissions from combustion of crude oil on water. Environmental Science and Technology 24, 1418±1427. Bourbon, P., Esclassan, J., Giroux, M., Vandaele, J., Lepert, J. C. and Savoya, L. (1986) Etude comparative et statistique des concentrations de HAP es site industrial et urbain (en relation avec d'autres polluants et des parametres climatiques). Polluting Atmospherique 36±42.

395

Marine Pollution Bulletin Budzinski, H., Jones, I., Bellock, J., Pierard, C., Garrigues, P. (1997) Evaluation of sediment contamination by polycyclic aromatic hydrocarbons in the Gironde estuary. Marine Chemistry 58, 85±97. Butler, J. D. and Crossley, F (1981) Reactivity of polycyclic aromatic hydrocarbons adsorbed on soot particles. Atmosphere Environment 15, 91±94. Cerniglia, C. E. and Heitkamp, M. A. (1989) In Microbial Degradation of PAH in the Aquatic Environment, ed. U. Vanarasi, pp. 41±68. CRC press, Boca Raton, FL. Colombo, J. C., Pelletier, E., Brochu, C., Khalil, M. and Cataggio, J. A. (1989) Determination of hydrocarbon sources using n-alkanes and polyaromatic hydrocarbon distribution indices. Case study: Rio de la Plata estuary, Argentina. Enviromental Science and Technology 23, 888±894. Garrigues, P., Narbonne, J. F., Lafaurie, M., Ribera, D., Lemaire, P., Raoux, C., Michel, X., Salaun, J. P., Monod, J. L. and Romeo, M. (1993) Banking of environmental samples for short-term biochemical and chemical monitoring of organic contamination in coastal marine environments: the GICBEM experience (1986±1990). Science Total Environment 139/140, 225±236. Grimmer, G. and B ohnke, H. (1975) Pro®le analysis of polycyclic aromatic hydrocarbons and metal contents in sediment layers of a lake. Cancer. Let. 1, 75±84. Gschweng, P. M. and Hites, R. A. (1981) Fluxes of polycyclic aromatic hydrocarbons to marine and lacustrine sediments in the northeastern United States. Gechimica et Cosmochimica Acta 45, 2359±2367. Heit, M., Tan, Y., Klusek, C. and Burke, J. C. (1981) Anthropogenic trace elements and polynuclear aromatic hydrocarbon levels in sediment cores from two lakes in the Adirondak acid lake region. Water, Air and Soil Pollution 15, 441±464. Lake, J. L., Norwood, C., Dimock, C. and Bowen, R. (1979) Origins of polycyclic aromatic hydrocarbons in estuarine sediments. Geochimica et Cosmochimica Acta 43, 1847±1854. Lehr, R. E. and Jerina, D. M. (1977) Metabolic activation of polycyclic aromatic hydrocarbons. Archives of Toxicology 39, 1±6. Louda, J. W. and Baker, E. W. (1984) Perylene accurrence, alkylation and possible source in deep sea sediments. Geochimica et Cosmochimica Acta 48, 1043±1058. McElroy, A. E., Farrington, J. W. and Teal, J. M. (1989) In Bioavailability of polycyclic aromatic hydrocarbons in the aquatic environment, ed. U. Vanarasi, pp. 1±40. CRC press, Boca Raton, FL. Mill, T., Mabey, W. R., Lan, B. Y. and Baraze, A. (1981) Photolysis of polycyclic aromatic hydrocarbons in water. Chemosphere 10, 1281± 1290. Monin, J. C., Pelet, R. and Fevrier, A. (1978) Analyse geochimique de la matiere organique extraite des roches sedimentaires. IV. Extraction des roches en faibles quantites. Rev. Inst. Fr. de P etr., MarsAvril 1978 33 (2), 78012. Muel, B. and Saguem, S. (1985) Determination of 23 polycyclic aromatic hydrocarbons in atmospheric particulate matter of the Paris area and photolysis by sun light. International Journal Environmental Analytical Chemistry 19, 111±131.

396

Ne€, J. M. (1979) Polycyclic aromatic hydrocarbons in the aquatic environment, sources, fates, and biological e€ects. Applied Science, London, Great Britain, 262 pp. Parlanti, E. (1990) Utilisation des hydrocarbures comme traceurs dÕorigine de la matiere organique sedimentaire en mileu marin. Etude du Golfe du Lyon et du Golfe de Gascogne (Programme Ecomarge) PhD thesis Nr 495, University Bordeaux I, Bordeaux, France; 289 pp. Quilliam, M. A., Hardsta€, W. R., Analecto, J. F., Leblanc, M. D., Stergiopoulos, V., Dick, K. L., Bowser, M. T., Curtis, J. M., Embree, D. J., Greig, Sim, P. and Boyd, K. (1994) Preparation and certi®cation of solutions of predeutered polycyclic aromatic compundsintended for use as surrogate standards. Fresenius Z. Analytical Chemistry 350, 109±118. Raoux, C. (1991) Modelisation du mecanisme de contamination par des hydrocarbures aromatiques polycycliques (HAP) des sediments marins c^ otiers de Mediterranee: consequences sur la biodisponibilite des HAP dans le milieu marin. PhD Thesis, Nr 565, University bordeaux I, Bordeaux, France; 136 pp. Raoux, C. Y. and Garrigues, P. (1993) Mechanism model of polycyclic aromatic hydrocarbons contamination of marine coastal sediments from the Mediterranean sea. In Proceedings of the 13th International Symposium on Polynuclear Aromatic Hydrocarbons, pp. 443±450. Bordeaux, France, Gordon and Breach Publishers. Readman, J. W., Mantoura, R. F. C. and Rhead, M. M. (1984) The physical-chemical speciation of polycyclic aromatic hydrocarbons (PAH) in aquatic systems. Fresenius Z. Analytical Chemistry 319, 126±131. Sicre, M. A., Marty, J. C. and Saliot, A. (1987) Aliphatic and aromatic hydrocarbons in di€erent sized aerosols over the mediterranean sea: occurrence and origin. Atmosphere Environment 21, 2247± 2259. Smith, J. N. and Levy, E. M. (1990) Geochronology of polycyclic aromatic hydrocarbon contamination in sediments of the Saguenay Fjord. Environmental Science and Technology 24, 874± 879. Soclo, H. H., Garrigues, P. and Ewald, M. (1986) Analyse quantitative des hydrocrabures aromatiques polycycliques dans les sediments recents par chromatographie en phase liquide et detection spectro¯uorimetrique. Analusis 14 (7), 344±350. Soclo, H. H. (1986) Etude de la distribution des hydrocarbures aromatiques polycycliques dans les sediments recents. Identi®cation des sources. PhD Thesis, Nr 50, University Bordeaux I, Bordeaux, France, 158 pp. Venkatsen, M. I. (1988) Occurrence and possible sources of perylene in marine sediments ± a review. Marine chemistry 25, 1±25. Vo Dinh, T. and Martinez, P. R. (1981) Direct determination of selected PAH in a coal liquefaction product by synchronous luminecence techniques. Analytical Chemistry 125, 13±19. Wacaf II project (1988) Workshop, Accra, Ghana, April 1988. Wise, S. A., Hilpert, L. R., Rebbert, R. E., Sander, L. C., Schantz, M. M., Chesler, S. N. and May, W. E. (1988) Fresenius Z. Analytical Chemistry 332, 573±582.