Polycyclic aromatic hydrocarbons in surficial coastal ... - ARPAL

Baseline / Marine Pollution Bulletin 46 (2003) 903–917 907Polycyclic aromatic hydrocarbons in surficial coastal sedimentsof the Ligurian SeaR.M. Bertolotto a , F. Ghioni b , M. Frignani c, *, D. Alvarado-Aguilar c , L.G. Bellucci c ,C. Cuneo a , M.R. Picca a , E. Gollo ba Agenzia Regionale Protezione Ambiente Ligure (ARPAL), Direzione Scientifica, P.za Vittoria 15, 16121 Genova, Italyb Agenzia Regionale Protezione Ambiente Ligure (ARPAL), Dipartimento di Genova, V. Montesano 5, 16121 Genova, Italyc Istituto di Scienze Marine, Sezione di Geologia Marina, CNR, Via Gobetti 101, 40129 Bologna, ItalyKeywords: Polycyclic aromatic hydrocarbons; Sediments; Sources; Ligurian SeaPolycyclic aromatic hydrocarbons (PAHs) are a classof ubiquitous organic compounds with two to sevencondensed aromatic rings. Common characteristics ofPAHs are very low solubility in water, good affinity formany organic solvents, low volatility, except for the verylow molecular weight congeners, and a tendency to adsorbonto sediment particles. Sixteen PAHs are consideredby the US EPA as priority micropollutantsbecause of their carcinogenic and mutagenic properties(Arcos and Argus, 1975).PAHs have numerous sources, both natural and anthropogenic.They are naturally present in tar, bitumenand oil. Furthermore, certain compounds such as peryleneand retene are thought to be produced diagenetically(Wakeham et al., 1980b). Anthropogenic sourcesinclude combustion of fossil fuels, waste incinerationand production of coke, carbon black, coal tar pitch,asphalt and petroleum cracking (Hallet and Brecher,1984; and references therein; McCready et al., 2000).Spillage of fossil fuels is another common anthropogenicsource of PAHs. Pyrolytic and petrogenic sources areknown to generate substantially different PAH assemblages.In general, combustion products are dominatedby relatively high molecular weight (HMW) compoundswith four condensed rings or more. In contrast, mono-,bi- and tricyclic aromatic compounds (LMW) are mostabundant in fossil fuels (Prahl and Carpenter, 1983) andthese PAH mixtures contain high levels of alkylatedcongeners. Much work has been dedicated to the assessmentof PAH contamination levels coupled to theidentification of the sources through study of sediments(e.g. Youngblood and Blumer, 1975; Wakeham et al.,1980a; Canton and Grimalt, 1992; Soclo et al., 2000;McCready et al., 2000). The purpose of this study was todetermine distribution, degree of contamination, sourcesand potential toxicological significance of PAHs* Corresponding author. Tel.: +39-51-6398906; fax: +39-51-6398940.E-mail address: frignani@igm.bo.cnr.it (M. Frignani).in surficial sediments along the coast of the LigurianSea.The Ligurian Sea belongs to the northern part of thewestern Mediterranean. The coastal morphology of theLiguria Region is variable, and frequently cliffs dropsheer to the sea. The limited width of the coastal zonedetermines a gathering of the urban areas with a consequentconcentration of both civil and industrial presencein a narrow but highly populated territory. In particularGenova, but also other cities, have a long history of industrialand harbour activities, whereas long tracts of thecoast are dedicated to tourism. The circulation of theLigurian Sea is dominated by surface and intermediatecurrents that follow a cyclonic circulation. However,local circulation is responsible for the dispersion ofsediment material along the coast, and these longshorecurrents often cause an eastward oriented transport.Sampling was carried out in 1998 at 75 stations in the25 localities shown in Fig. 1. Three sediment sampleswere collected along transects at 500, 700 and 1000 mfrom the shoreline using a Van Veen grab, whose penetrationwas typically 10–20 cm. The topmost sediment(2 cm) was carefully removed with a stainless steel spoonand transferred to glass screw cap jars with aluminiumfoil lid liners. The sediment samples were stored at )18°C before analysis.PAHs determined included naphthalene (Na),1-methylnaphthalene (1mNa), 2-methylnaphthalene(2mNa), fluorene (Fl), phenanthrene (Phe), anthracene(An), fluoranthene (Flt), pyrene (Py), chrysene (Ch),benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF),benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP),indeno(1,2,3-cd)pyrene (IPy), dibenzo(a,h)anthracene(DBA), and benzo(g,h,i)perylene (Per). Results are thuspresented for 14 US EPA priority PAH congeners (all butacenaphthene and acenaphthylene) together with 1- and2-methylnaphthalene. Analyses were carried using a fluorimetricmethod modified from Kootstra et al. (1995).Approximately 15 g of homogenised wet sedimentwas extracted twice with 20 ml of acetone in an

Table 1Quality of the analytical resultsPAH Precision (%) Accuracy a (%) Accuracy b (%) Recovery (%) Detection limit (lg/kg)Naphthalene 6.2 91.2 – 87 8.8 0.16Fluorene 7.4 90.5 – 95.7 2.7 0.20Phenanthrene 6.2 82.7 – 80.4 5.9 0.14Anthracene 4.6 91.0 – 85.2 4.7 0.02Fluoranthene 3.1 85.5 – 82.9 8.1 0.60Pyrene 2.5 85.0 83.3 80.1 10.1 0.20Chrysene 4.9 96.1 – 94.4 2.8 0.10Benzo(a)anthracene 6.9 95.0 79.2 92.1 2.5 0.10Benzo(b)fluoranthene 5.5 96.1 96.9 93.7 4.7 0.18Benzo(k)fluoranthene 3.6 97.1 91.7 96.7 9.6 0.10Benzo(a)pyrene 5.3 95.8 94.8 92.4 2.5 0.12Dibenzo(a,h)anthracene 5.7 95.9 – 87.3 1.9 0.20Benzo(g,h,i)perylene 0.6 84.4 – 81.1 4.1 0.30Indeno(1,2,3-cd)pyrene 11.8 93.5 83.3 98 9.7 2.0a From additions of know amounts of standards.b From the certified material BCR CRM 535 (Freshwater harbour sediment).Baseline / Marine Pollution Bulletin 46 (2003) 903–917 909Genova using sieves to separate the fines (silt pus clay)from the coarser sediment. A Coulter Counter II wasused to quantify the fine sediment fractions.Fig. 1 shows that surface sediments contain a widerange of total PAH concentrations, from very low (

910 Baseline / Marine Pollution Bulletin 46 (2003) 903–917Table 2Analytical results for the 12 sites with the highest PAH concentrations and percent content of fine particlesFines(%)TotalPAH(lg/kg)Per(lg/kg)DBA(lg/kg)IPy(lg/kg)BaP(lg/kg)BkF(lg/kg)BbF(lg/kg)BaA(lg/kg)Ch(lg/kg)Py(lg/kg)Flt(lg/kg)An(lg/kg)Phe(lg/kg)Fl(lg/kg)2mNa(lg/kg)1mNa(lg/kg)Na(lg/kg)Province Transect Distancefrom thecoast(m)Savona Finale Ligure 1000 6.82 2.27 11.8 21.2 1427 465 3244 2931 2128 2042 3515