Polychlorinated Dibenzo-p-dioxins andDibenzofurans in Sur®cial Sediments ofthe Venice Lagoon (Italy)L. G. BELLUCCI *, M. FRIGNANI , S. RACCANELLIà and C. CARRARO§ Istituto di Geologia Marina del CNR, Via Gobetti 101, 40129 Bologna, ItalyàConsorzio Interuniversitaro Nazionale ``La Chimica per l ÕAmbiente'' ± Via della Libert�a 5/12- 30175 Marghera (VE),Italy§EniChem SpA, Stabilimento di P.to Marghera, Via della Chimica, P.to Marghera (VE), Italy

Concentrations of polychlorinated dibenzo-p-dioxins(PCDDs) and dibenzofurans (PCDFs) have been mea-sured in samples from 24 sites in the Venice Lagoon. Theyranged from 16 to 13 642 ng kgÿ1 (dioxins) and from 49 to126 561 ng kgÿ1 (furans), with TEQs spanning between0.5 and 2857 ng kgÿ1. The highest concentrations havebeen found in sediments of the canals of the 1st IndustrialArea. These sediments represent a potential risk for thelagoon environment because they can be episodically re-suspended by dredging operations or passage of ships.Lagoon sediments are much less contaminated. Threedi�erent PCDD/F congener pro®les have been identi®ed:one is mainly octachloro dibenzo-p-dioxin (OCDD) andcomes from combustion, the second is characterized by thealmost exclusive presence of octachloro dibenzofuran(OCDF) and can be associated to the stripping of vinylchloride monomer (VCM), the third contains signi®cantamounts of di�erent congeners, and was probably origi-nated by di�erent productions within the 1st IndustrialArea. Ó 2000 Elsevier Science Ltd. All rights reserved.

Keywords: sediments; PCDDs; PCDFs; Venice Lagoon;urban and industrial pollution; sources of contaminants.

Polychlorinated dibenzo-p-dioxins (PCDDs) anddibenzofurans (PCDFs) are ubiquitous, very toxic con-taminants, which arise from a number of well-identi®edsources including incineration, chemical manufacturingprocesses involving the use of chlorine, sewage sludge,vehicle exhausts and domestic ®res (Swerev and Balls-chmiter, 1989). These chemicals display high a�nity forparticulate matter and accumulate in sediments(Dannenberg et al., 1997). In recent years the VeniceLagoon environment has been heavily a�ected by an-thropogenic activities and uncontrolled discharge ofpollutants from both di�use and point sources (Pavoni

et al., 1987). Dioxins and furans became a major con-cern for the Municipality of Venice in 1995, when theenvironmentalist organization Greenpeace revealed aheavy pollution of sediments (Marcomini et al., 1997)but the ®rst researches had started in 1992 with the workof Turrio Baldassarri et al. (1994) and Fattore et al.(1997) who analysed the same set of samples of sur®cialsediment (the thickness of the layer considered was notspeci®ed) including ®ve sites in the lagoon and one in theAdriatic Sea. The highest values were found in a canal ofVenice and in sediment close to the industrial area ofPorto Marghera, but the degree of contamination wasconsidered moderate.

Recently, di Domenico et al. (1998), Jimenez et al.(1998) and Ramacci et al. (1998) presented their resultson the PCDD/F contamination of Venice Lagoon andnearby Adriatic sediments. A comprehensive review onthis subject had been published by Marcomini et al.(1997). The data show that both civil and industrialactivities contributed signi®cantly to the contaminationof lagoon sediments. The authors maintain that twopro®les of PCDD/Fs can be recognized: one is due tountreated domestic sewage and combustion (Fattoreet al., 1997) and prevails in sediments of urban areas,while the other is widely distributed and imputed to theproduction of vinyl chloride monomer (VCM). DiDomenico et al. (1998) stated that all the PCDD/Fpro®les in the lagoon are derived by the combination ofthese two. According to these authors the total toxicityequivalents (TEQs) span from 0.35 to 8.5 ng kgÿ1 inlagoon sediments, from 12 to 570 ng kgÿ1 in industrialcanals, from 5 to 23 ng kgÿ1 in the canals of Venice andMurano, and from 0.07 to 17 ng kgÿ1 in Adriatic Sedi-ments. The same authors found the highest levels (570ng kgÿ1) in a sample obtained by mixing sediments takenfrom di�erent locations in the Nord Industrial Canal.

This paper discusses the presence of PCDDs andPCDFs in sur®cial sediments of the central Venice La-goon in order to assess the degree of pollution and the

Marine Pollution Bulletin Vol. 40, No. 1, pp. 65±76, 2000

Ó 2000 Elsevier Science Ltd. All rights reserved

Printed in Great Britain

0025-326X/00 $ - see front matterPII: S0025-326X(99)00171-X

*Corresponding author. E-mail: bellucci@igm.bo.cnr.it

65

relative importance of the sources. To do that, wesampled lagoon sediments, canals of the industrial areaand salt marshes.

Study Area and Sampling Strategy

Study area and sampling locations are shown in Figs.2±4. We studied the industrial canals and part of thecentral lagoon closest to the industrial area of PortoMarghera. The sampling strategy was designed to un-derstand the relative importance of the sources ofPCDDs and PCDFs. Salt marshes M1 and M2 werestudied to assess the in¯uence of the atmospheric de-livery: since the wind blows prevailingly in a NE±SWdirection, site M1 is windward and M2 is leeward withrespect to both the urban and the industrial areas.Among the four lagoon samples, E1 was chosen becauseit can be directly in¯uenced by industrial pollution(Frignani et al., 1998) and E14 because it represents thezone near the incinerator and may have accumulateddioxins from this source.

Data regarding sediment densities and compositions,metal pollution, and role of eutrophication on the be-haviour of trace metals were provided by Cossu andDeFraja Frangipane (1985), Zonta et al. (1992), Sfrisoet al. (1995). Sediment grain size composition is ratherheterogeneous because of the intense water dynamicsclose to the main lagoon channels, and ®ne materials areabundant principally close to the mainland and at thecentre of mud ¯ats (Zonta et al., 1992). The scienti®cliterature regarding the industrial area is surprisinglyscarce. Some information was provided by Pavoni et al.(1987) and by Ramacci et al. (1998). In the industrialarea about 130 outfalls have been identi®ed but only 20are permanently active, the others being used to drainmeteoric waters (Ramacci et al., 1998). Factories areconnected to treatment plants since the early 1980s,whereas before sewages were less e�ciently treated.Some canals have been partially dredged at di�erenttimes in order to prevent in®lling and allow the passageof ships. For instance, the terminal part of the NordIndustrial Canal was dredged in 1997.

Materials and Methods

Sediments were taken from eighteen sites in the in-dustrial canals and four in the lagoon. Sampling wascarried out at di�erent times in May 1996, February1997, January and March 1998 by means of a manualpiston corer. In the Malamocco±Marghera Canal and inthe Nord Industrial Canal, where water depth is higherthan 2.5 m, a small gravity corer was used. Salt marshesM1 and M2 were sampled inserting a plexiglass tubeinto the sediment.

Cores were immediately extruded to obtain mostly 2cm thick sections which were put in glass jars with al-

uminium foil caps. In some cases sections were thicker,up to 8 cm in the case of the sandy and incoherentsediment at C14. Samples were then frozen and stored atÿ18°C until the analysis. A separate core was taken ateach location for the other analyses (heavy metals, grainsize, organic carbon, radiotracers). These cores wereextruded in situ and sectioned at intervals of 2 cm.

The analysis of chlorinated organic compounds wascarried out using established GC±MS methods (EPA1613/94/revision b) for the determination of 17congeners 2,3,7,8 substituted of PCDDs and PCDFs.Wet samples were freeze-dried and then ground to ®nepowder. Then 10 g were spiked with a series of 15 13C-labelled PCDD/F congeners as internal standards, andsoxhelet extracted with toluene. The extracts weretransferred to hexane and treated with sulphuric acid(98%) and potassium hydroxide (20%) in a separatoryfunnel. The clean-up procedure was completed usingpre-packed disposable columns containing multilay-er silica, alumina and carbon in the automatic threecolumn system Dioxin Prep (Fluid Management Sys-tem Inc.). The HRGC/HRMS analyses were carried outusing an HP 6890 Plus gas chromatograph coupled to aFINNIGAN MAT 9SS mass spectrometer operating inEI mode at 70 eV with a resolution of 10.000 (10%valley). Sample injections were performed in the split-less mode on di�erent columns: (a) 30 m (0.25 mmID, 0.25 lm ®lm), Restek RTX 5MS or J&W DB5MS; (b) 60 m RTX 5MS (Restek 0.25 mm ID, 0.25lm ®lm); (c) 30 m Rtx 200 (Restek 0.25 mm ID, 0.25 lm®lm) for veri®cation. Fig. 1 shows three ion currentpro®les relative to very di�erent samples. Thequantitative determination of PCDD/Fs was performedby an isotope dilution method using relative responsefactors previously obtained from ®ve standard solutionsinjections (EDF 9999 Cambridge Isotope Laborato-ries, Woburn, MA), as recommended by the US-EPA. GC/MS system performance and calibration wereveri®ed daily for all PCDD/Fs and labelled com-pounds with the CS3 calibration veri®cation standardand the isomer speci®city test standard. Recoveries werealways between 40% and 120%, with a variationcoe�cient of 20% (for the low values) or better. Blankswere obtained analysing uncontaminated naturalsamples: a calcareous rock and a coastal sand. Thesesamples, run once a week, gave PCDD/F concentrationsand TEQs always lower than 80 and 0.02 ng kgÿ1,respectively.

Organic carbon (OC) contents were obtained using aCHN analyser, after elimination of the carbonate frac-tion with HCl directly in a silver capsule. Grain sizeanalyses were carried out by wet sieving, to separatesands, after a pretreatment with H2O2. Core sampleshave been used to obtain the history of pollution and theresults will be discussed elsewhere. All concentrationsare referred to dry weight.

66

Marine Pollution Bulletin

Fig. 1 Ion current pro®les of native PCDD/F congeners (from tetrato octa substituted) relative to samples C12 (a), C11 (b) andM1 (c). Note that the scale expansion used for M1 is 100 timeshigher than the others. The chromatographic column is a 30 mJEW DB5 MS.

67

Volume 40/Number 1/January 2000

Results and Discussion

Micropollutant concentrations and distributionsThe analytical results are given in Table 1. PCDD and

PCDF concentrations, as sums of congeners 2,3,7,8substituted, are listed in Table 2 together with toxicequivalents (TEQs), which sum the seventeen 2,3,7,8-substituted congeners on the basis of their toxicequivalence to 2,3,7,8-TCDD (US EPA, 1989). PCDDconcentrations in sur®cial sediments range from 67 to13 642 ng kgÿ1 in the industrial canals and from 33 (E9)to 273 (E1) ng kgÿ1 in the lagoon. Similarly, PCDFconcentrations in sur®cial sediments range from 592 to126 550 ng kgÿ1 in the industrial canals and from 206 to1976 ng kgÿ1 in the lagoon. In terms of TEQs, the levelsare 2.3±2857 and 1.9±34 ng kgÿ1 in canal and lagoonsediments, respectively.

The distribution of TEQs in sur®cial samples of theindustrial canals is displayed in Fig. 2. The concentra-tion gradient is similar to that shown by metals(Frignani et al., 1998) but much stronger: the maximumvalue (2857 ng kgÿ1) characterizes sample C12, locatedin the Brentella Canal, but very high values have beenalso found in the Nord Industrial Canal (938±1712 ngkgÿ1) and in the Salso Canal (566 ng kgÿ1). This maxi-mum is 29±1000 times higher than the levels found atother locations inside the 2nd Industrial Area. In par-ticular, concentrations in the highly polluted zone are18±119 times that found at C11, representative of arelatively ®ne sediment from the Brentelle Canal, whereplants for the production of VCM discharged withoutcontrol until 1980. Our results, divided for the di�erentsubareas, are compared with those reported by diDomenico et al. (1998) in Table 3. Most of our valuesare consistent with the values found by the other authorsbut we revealed that exceptionally high concentrationscharacterize areas not or scarcely considered by previousstudies. In particular, di Domenico et al. (1998) hadalready found very high concentrations in sediments ofthe Nord Industrial Canal, but they did not have thepossibility to further explore the PCDD/F distributionthere. On the other hand, a comparison between ourresults and previous data is not straightforward: theproblem is that literature values are not relative to real``sur®cial samples'' because they represent layers of un-de®ned thickness or, sometimes, tens of centimetresthick, whereas we have always chosen to sample with ahigh vertical resolution. Table 4 shows that the con-tamination of the industrial canals of the Venice Lagoonis high, compared to other areas worldwide.

Fig. 3 shows the pattern of TEQ concentrations inlagoon and marsh samples, together with some selectedvalues from industrial canals for comparison. Sur®cialsamples from the lagoon (E1, E3, E9, E14) are charac-terized by low concentrations with respect to thosefound in nearby industrial canals. The big di�erencebetween TEQ concentrations between the canals of the1st Industrial Area and the lagoon sample E1, suggests

that polluted sediments of these canals are relativelyimmobile. We think that they can be resuspended anddisplaced only by episodic events, such as dredging op-erations or passage of ships, and have some in¯uence onthe contamination of site E1, which shows TEQ con-centrations of PCDD/Fs that are three times higher withrespect to site E14, close to the town of Venice and tothe old incinerator, active until 1983.

Concentrations of PCDD/Fs in marsh sur®cial sam-ples do not re¯ect the real distribution of atmospheric¯uxes: we know that salt marsh M2 recorded concen-trations one order of magnitude higher than M1, asshown by some metals (Bellucci et al., 1999), due to theprevailing SW direction of winds in the area. The dis-crepancy shown by sur®cial samples is due to a processof marsh degradation occurring at M2 (Bellucci et al.,1999). The data of Tables 1 and 2 show a di�erentcomposition of the ¯uxes: PCDFs are high at M2, due tothe in¯uence of the industrial area, whereas PCDDs arerelatively more abundant at M1.

Role of sediment featuresThe comparison of micropollutant concentrations in

sediments is better accomplished through a normaliza-tion against a common parameter (Lohse, 1991;Dannenberg et al., 1997) because organic micropollu-tant distribution is driven by the combination of factorssuch as proximity to the sources, grain size compositionof sediments, content of apolar lipid material and par-titioning coe�cient (Tyler and Millward, 1996). Wemeasured grain size compositions and organic OCcontents so as to check the role of these sedimentcharacteristics on PCDD/F distribution. The normal-ized data are reported in Table 2, together with originalresults.

It is evident that the strong concentration gradientbetween the two industrial areas cannot be determinedby di�erences in the grain size composition of samplesand/or in their organic carbon content. Organic carbonis particularly high in the Brentelle Canal (2nd Indus-trial Area), and the normalization against OC increasesthe di�erence between sites C9 and C11, and the mostpolluted sites C10, C12 and C13. On the other hand, thenormalization against grain size (the concentration iscalculated assuming that contaminants are linked onlyto the ®ne fraction) substantially con®rms the previousdistribution. The only relevant di�erence is relative tosample C9, due to the very low content of ®nes (8.4%).This normalization makes values of TEQs in samples C9and C11 very similar, showing that the ®ne sediment hasalmost the same TEQ concentration in the BrentelleCanal. This is due to the fact that the two sites have beenin¯uenced by the same sources.

On the other hand, there are sites in the same canal,such as C1, C15 and C16 in the Sud Industrial Canal,that are characterized by very di�erent TEQ values: 8.7,98, and 65 ng kgÿ1, respectively. These discrepancies arenot due only to OC content and grain size composition

68

Marine Pollution Bulletin

TABLE

1

Analyticalresults:concentrationsofthe17congeners2,3,7,8

substitutedofPCDDsandPCDFsin

sur®cialsedim

ents.a

Site

Level

(cm)

2,3,

7,8-

1,2,3,

7,8-

1,2,3,

4,7,8-

1,2,3,

6,7,8-

1,2,3,

7,8,9-

1,2,3,4,

6,7,8-

1,2,3,4,

6,7,8,9-

2,3,

7,8-

1,2,3,

7,8-

2,3,

4,7,8-

1,2,3,

4,7,8-

1,2,3,

6,7,8-

1,2,3,

7,8,9-

2,3,4,

6,7,8-

1,2,3,4,

6,7,8-

1,2,3,4,

7,8,9-

1,2,3,4,

6,7,8,9-

TCDD

PeC

DD

HxCDD

HxCDD

HxCDD

HpCDD

OCDD

TCDF

PeC

DF

PeC

DF

HxCDF

HxCDF

HxCDF

HxCDF

HpCDF

HpCDF

OCDF

C1

0±2

<0.010

<0.010

<0.015

<0.015

<0.015

<0.020

0.095

0.012

<0.010

<0.010

0.048

<0.015

<0.015

<0.015

0.171

0.025

0.599

C2

0±2

<0.010

<0.010

<0.015

<0.015

<0.015

0.023

0.123

0.015

0.012

<0.010

0.064

0.021

<0.015

<0.015

0.210

0.034

0.654

C3

0±2

<0.010

<0.010

<0.015

<0.015

<0.015

0.052

0.333

0.026

0.020

0.014

0.095

0.031

<0.015

<0.015

0.416

0.056

1.272

C4

0±2

<0.010

<0.010

<0.015

<0.015

<0.015

0.053

0.401

0.027

0.017

0.013

0.072

0.023

<0.015

<0.015

0.487

0.035

1.276

C5

0±2

<0.010

<0.010

<0.015

<0.015

<0.015

0.049

0.403

0.025

<0.010

0.015

0.042

<0.015

<0.015

<0.015

0.443

<0.020

1.239

C6

0±2

<0.010

<0.010

<0.015

<0.015

<0.015

0.073

0.487

0.032

0.023

0.019

0.121

0.034

0.019

<0.015

0.432

0.066

1.425

C9

0±2

<0.001

<0.001

<0.003

<0.003

<0.003

0.007

0.060

0.004

0.002

0.001

0.005

<0.003

<0.003

<0.003

0.040

<0.003

0.540

C10

0±3

<0.001

0.032

<0.002

0.070

0.087

0.995

3.931

0.644

<0.001

0.423

3.696

1.128

0.766

0.115

11.849

1.960

26.500

C10B

0±4

0.010

0.021

0.037

0.044

0.053

<0.005

2.154

0.368

0.277

0.265

2.079

0.590

0.438

0.096

6.162

1.141

11.966

C11

0±2

<0.001

<0.001

<0.003

<0.003

<0.003

0.037

0.349

0.029

0.013

0.014

0.048

0.015

0.009

<0.003

0.164

0.018

3.793

C12

0±2

0.040

0.101

0.152

0.208

0.184

2.645

10.311

1.602

1.456

1.136

8.793

2.742

1.973

0.355

28.333

5.687

74.484

C13

0±2

0.008

0.014

0.027

0.030

0.046

0.092

2.401

0.239

0.313

0.172

2.015

0.490

0.364

0.342

6.257

1.133

16.337

C14

0±8

<0.001

0.005

0.035

0.044

0.019

0.047

0.233

0.020

0.018

0.018

0.118

0.035

0.022

0.007

0.422

0.070

1.254

C15

0±4

<0.001

<0.003

<0.003

0.011

0.006

0.117

0.703

0.061

0.050

0.045

0.357

<0.003

0.076

0.014

1.247

0.120

4.311

C16

0±2

<0.001

<0.003

0.004

0.003

<0.003

0.056

0.173

0.017

0.014

0.093

0.072

0.021

0.013

0.004

0.255

0.041

0.720

C17

0±3

<0.001

<0.003

<0.003

<0.003

<0.003

<0.003

0.268

0.018

0.011

0.011

0.097

0.030

0.020

<0.003

0.322

0.050

1.099

C18

0±4

<0.001

0.057

0.125

0.110

0.080

1.709

7.510

0.801

0.935

0.652

6.037

1.643

1.339

0.153

17.631

3.637

44.518

C19

0±3

<0.001

0.015

0.030

0.025

0.015

0.439

2.273

0.200

0.147

0.175

1.416

0.382

0.284

0.075

5.173

0.918

14.728

E1

0±3

<0.001

<0.001

<0.002

0.003

<0.002

0.050

0.221

0.021

0.029

<0.010

0.143

0.046

0.033

<0.002

0.571

0.076

1.056

E3

0±3

<0.010

<0.010

<0.015

<0.015

<0.015

<0.020

0.035

<0.010

<0.010

<0.010

0.017

<0.015

<0.015

<0.015

0.067

<0.020

0.130

E9

0±3

<0.001

<0.001

<0.003

<0.003

<0.003

0.006

0.027

0.003

<0.003

<0.003

0.014

0.005

0.003

<0.003

0.064

<0.003

0.117

E14

0±3

<0.001

<0.001

<0.002

<0.002

<0.002

0.020

0.119

0.012

<0.001

<0.001

0.042

0.013

0.009

<0.002

0.166

0.016

0.242

M1

0.5±1<0.001

0.001

<0.003

<0.003

<0.003

0.013

0.110

0.004

0.002

0.005

0.002

<0.003

0.003

0.001

0.018

<0.003

0.022

M2

0.5±1<0.001

<0.001

<0.003

<0.003

<0.003

0.003

0.009

0.001

<0.001

<0.001

0.003

<0.003

<0.003

<0.003

0.013

<0.003

0.034

aNote

thatvalues

are

inlg

kgÿ1.

69

Volume 40/Number 1/January 2000

(Table 2) but could be ascribed to the in¯uence of sec-ondary discharges and to the scarce mobility of thesecontaminants, or to the dishomogeneous e�ects of var-ious dredging operations. The same holds for concen-trations of PCDD/Fs in the canals of the First IndustrialArea: the highest TEQ values are those of the BrentellaCanal, where ®ne sediments predominate, but they areprobably also the result of direct dumping into this ca-nal (there was an outfall from nearby factories that wasdiverted in the mid 1980s to join the wastes delivered tothe treatment plant). The relatively high value found inC14 is due to the size of the sample, representing a layer8 cm thick, which accounts for a mixture of old andpresent inputs. This site is in¯uenced by materialscoming from the most polluted zones of the 1st Indus-trial Area through the Malamocco±Marghera Canal,and from the outfall of the treatment plant of the mu-nicipal and industrial wastes. In the Ovest IndustrialCanal, TEQ concentrations span between 21 and 39 ngkgÿ1, whereas the range of normalized value is 23±58 ngkgÿ1, without a signi®cant variation. It should be notedthat C6, which shows the highest level, is located deepinside the 1st Industrial Area. In the Nord IndustrialCanal, values of samples C10, C10B and C18 becomemore comparable after normalization against grain size.

Source identi®cationUnder certain conditions it is possible to elucidate the

source of dioxins and furans found in environmentalsamples by comparing their homologue or congener

pro®les with characteristic source pro®les (Swerev andBallschmiter, 1989; Hagenmeier et al., 1994; Cleverlyet al., 1997). This approach, already followed by otherauthors (Fattore et al., 1997; Marcomini et al., 1997; diDomenico et al., 1998; Ramacci, 1998), can be mis-leading in the absence of a complete data set. Because ofthis, our identi®cation of the sources is based on a largenumber of sites and takes into account both gradientsand pro®les. Our homologue pro®les (histograms of permil 2,3,7,8 chlorosubstituted homologues referred to thesum of all isomers with a concentration above detectionlimits: Marcomini et al., 1997) are shown in Fig. 4, to-gether with their areal distribution.

The pro®les we obtained are fairly similar to thosealready described in the literature, with the exception ofthose characteristic of samples C9 and C11, collected inthe Brentelle Canal. Therefore, contrary to the otherauthors who identi®ed only two pro®les of PCDD/Fs inlagoon and canal sediments (di Domenico et al., 1998;Fattore et al., 1997; Ramacci et al., 1998), we foundthree of them (Fig. 4) that should correspond to as manyprincipal sources: (1) OCDD is produced by the bulk ofcombustion processes (tra�c, incinerators, electricpower plants, heating), is widely distributed through theatmosphere but can be found also in untreated domesticsewage, urban wastes and boat exhausts (with a speciale�ect of the two cycle engines cooled by salt water).Because of this, OCDD prevails in sediments of theGrand Canal (Fattore et al., 1997; Marcomini et al.,1997) and in sediments of salt marsh M1, close to

TABLE 2

Concentrations of PCDDs, PCDFs, TEQs, OC and ®ne sediments.a

Station Level PCDDs PCDFs TEQs OC Silt+clay TEQs TEQs(cm) (ng kgÿ1) (ng kgÿ1) (ng kgÿ1) (%) (%) (ng gÿ1 OC) (ng kgÿ1 ®nes)

C1 0±2 95 855 8.7 0.69 47.44 1.26 18.3C2 0±2 146 1010 14 0.92 43.69 1.52 32.0C3 0±2 385 1928 30 1.98 97.80 2.54 30.7C4 0±2 454 1950 27 2.28 97.18 1.18 27.8C5 0±2 452 1764 21 2.80 92.09 0.75 22.8C6 0±2 560 2171 39 1.87 67.86 2.09 57.5C9 0±2 67 592 2.3 0.57 8.40 0.40 27.4C10 0±3 5181 47 083 938 1.84 49.14 51.0 1909C10 B 0±4 2896 23 382 624 1.82 55.01 34.3 1134C11 0±2 386 4103 24 3.31 83.40 0.73 28.8C12 0±4 13 642 126 561 2857 2.65 82.45 107.8 3464C13 0±2 2618 27 661 566 1.86 34.79 30.4 675C14 0±8 373 1984 49 1.29 46.99 3.80 104C15 0±4 837 6371 98 1.58 82.21 6.20 119C16 0±2 236 1250 65 2.38 62.61 2.73 104C17 0±3 268 1658 27 4.70 42.51 0.57 64C18 0±4 9591 77 346 1712 2.24 90.74 76.4 1887C19 0±3 2797 23 318 427 1.74 87.68 24.5 1953

E1 0±3 273 1976 34 1.58 78.06 2.15 43.6E3 0±3 43 236 1.9 0.67 43.94 0.28 4.32E9 0±3 33 206 3.3 0.31 19.50 1.06 16.9E14 0±3 140 500 10 1.05 97.15 0.95 10.3

M1 0.5±1 124 56 4.4 4.30 98.89 0.10 4.44M2 0.5±1 16 49 0.5 1.70 92.69 0.03 0.54

a TEQ concentrations normalised against OC and grain size are also reported. In the case of marsh cores we analysed the section 0.5±1 because thetopmost sediment is full of roots.

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Fig.2

DistributionofTEQsofPCDD/Fsin

sur®cialsedim

ents

of

industrialcanals.Note

thathistogramsontherightsideare

notin

scale

withtheothers.

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Venice; (2) the second pro®le shows the almost exclusivepresence of OCDF (ca. 90%) and OCDD (ca. 10%), andis a characteristic of sediments from the Brentelle Canal.According to Stringer et al. (1995) a pro®le with pre-

vailing OCDF can be referrable to the stripping ofvinyl chloride. Therefore, the presence of OCDF in theBrentelle Canal sediments could be associated tothe VCM plants of the 2nd Industrial Area. The

Fig. 3 Distribution of TEQs of PCDD/Fs in sur®cial lagoon andmarsh sediments; some samples from the industrial area arereported for comparison. Note the di�erent scale of somehistograms.

TABLE 4

Comparison of data from di�erent locations. We considered only 2,3,7,8 substituted congeners, except when speci®ed. The TEQs are recalculatedfrom the original data.

Locations PCDDs (ng kgÿ1) PCDFs (ng kgÿ1) TEQs (ng kgÿ1) Reference

Western Baltic Sea and Oder River Est. System 9±2602 2±491 0.1±17.5 Dannenberg et al. (1997)Umber Estuary, UK 1915±2777a 738±1054a 14±24 Tyler and Millward (1996)Black Rock Harbour, Bridgeport, CT, USA 18 226±19946b 4367±4608b 223±250b Norwood et al. (1989)New Bedford Harbour, MA, USA 1707±7564b 258±7543b 10±761b Norwood et al. (1989)Chemieharbour, The Netherlands 2484±5752 39 123±89 395 434±923 Evers et al. (1989)St. Laurensharbour, The Netherlands 3670±31 994 3065±19 956 352±1849 Evers et al. (1989)Frierfjorden, Norway 30 550±70 870 274 900±401 200 6234±19 444 Oehme et al. (1989)

aAs sum of all congeners.bCongeners with nondetected values are not considered.

TABLE 3

TEQ concentrations (original and normalised data) in the various subzones and comparison with literature values.

Locations TEQsa (ng kgÿ1) TEQs (ng kgÿ1) TEQs (ng gÿ1 OC) TEQs (ng kgÿ1 ®nes)

Sud Industrial Canal 57 8.7±98 0.57±6.20 18.3±119Brentelle Canal. ± 2.3±24 0.40±0.73 27.4±28.8Ovest Industrial Canal 32±48 21±39 0.75±2.09 27.8±57.5Malamocco±Marghera Canal 12±130 14±49 1.52±3.80 32.0±104Nord Industrial Canal 570 938±1712 34.3±76.4 1134±1909Brentella Canal ± 427±2857 24.5±107 1953±3464Salso Canal ± 566 30.4 675Lagoon 0.3±20 1.9±34 0.28±2.15 4.32±43.6Marshes ± 0.5±4.4 0.03±0.10 0.54±4.44

a di Domenico et al. (1998).

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Fig.4

Homologuepro®lesofPCDD/Fsin

sedim

ents;asample

from

thetown

ofVenice(M

arcominiet

al.,1997)is

shown

for

comparison.

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concomitant presence of some OCDD, the depth dis-tribution in sediment cores (Frignani et al., submitted),and the available information on industrial activitiesand discharges (L. Liubicich, personal communication)suggest that present contamination is especially due tothe wastes of a plant for the production of liquid gases,which concentrates the atmospheric pollutants. A cer-tain contribution can be also provided by the runo� of170 ha of land in the 2nd Industrial Area, discharged bythe same outfall; 3) the third pro®le, containing mainlyPCDFs, with a prevailing component of OCDF, can befound in all the other canals of the industrial area, inlagoon and marsh sediment (site M2) and belongs tomaterials that, according to the information provided bygradients, were discharged in the Brentella Canal and inthe Nord Industrial Canal, where very high concentra-tions have been found. The pro®le remains the sameeverywhere, independently from the concentration ofPCDD/Fs that can be in¯uenced by the distance fromthe source and sediment composition. This congenerpro®le has always been considered the so-called ``chlo-rine ®ngerprint'' and attributed to the discharge ofVCM plants. Ramacci et al. (1998) found it intheir sample S2, relative to the e�uents of the 1,2dichloroethane/vinyl chloride monomer (DCE/VCM)manufacturing plant discharging into the Malamocco±Marghera Canal, close to our site C2. However, thiscannot be considered the principal source, because thismaterial is much more concentrated in sediments of the1st Industrial Area, relatively far from the DCE/VCMplants. A similar pro®le was ascribed to the productionof chlorinated aliphatic hydrocarbons by Stringer et al.(1995), but it is known that a number of other industrialactivities and burning plants can produce similar pro-®les, even magnesium chloride production (Wenninget al., 1992; Oheme et al., 1989). Our hypothesis is thatthe production of coke, related chemicals and metals inthe 1st industrial area may have been responsible for thiskind of pollution: a distillery of coke, which used saltwater for cooling, was active from 1930 to 1994, andaluminium and other non-ferrous metal foundries usedrecycled materials from 1950 to 1997.

A comparison of the distribution of the three pro®lesof PCDD/Fs shows a clear di�erentiation of the sourceseven in those samples where the various inputs aresummed together: a cluster analysis of pro®les (Hag-enmaier et al., 1995) clearly separates the samples inthree groups, corresponding to the prevalence of one ofthe three end members on the basis of the most impor-tant component. The result is shown in Fig. 5. Theanalysis groups together a sample taken from the GrandCanal in Venice (Fattore et al., 1997; Marcomini et al.,1997a) and the salt marsh site M1 that are prevailinglycontaminated by OCDD, and thus by the processes ofcombustion, even though some industrial-derived con-taminants can be present. At these sites the role of at-mospheric delivery is prevailing or signi®cant. A secondgroup is that represented by samples taken from the

Brentelle Canal. It is possible that this channel, char-acterized by low depth and high water ¯ows from boththe Lusore Canal and the outfall SM2, is not easily in-¯uenced by particles coming from other parts of theindustrial area. All the other sites have a commonPCDD/F pattern. Among the others, sites M2 and E14seem to contain a more signi®cant proportion of PCDD,mainly OCDD, probably due to the atmospheric deliv-ery and to the in¯uence of urban sources. Concentra-tions at sites M1 and M2, however, suggest that presentatmospheric ¯uxes are very low. The presence of mate-rials with some other PCDD/F pro®les in the outfallsdelivering wastes to the Malamocco±Marghera Canalhas been reported by Ramacci et al. (1998). The con-tribution of these sources seems not to have signi®cantlyaltered the prevailing patterns. Furthermore, the di�er-ent partitioning coe�cient of congeners can have thee�ect of masking the source identi®cation (Tyler andMillward, 1996) but this should be true when concen-trations are very low, which is not our case, and thethird congener pro®le, which is almost the same every-where, probably is not very in¯uenced by these selectionmechanisms.

Conclusions

Results can be summarized as follows:1. Sediments of the 1st Industrial Area show very

high TEQ concentrations: 938±1712, 427±2857,566 ng kgÿ1 in canals Nord, Brentella and Salso,respectively. Values characteristic of the otherchannels are much lower (2.3±98 ng kgÿ1);

2. Lagoon sediments are much less contaminated(3.3±34 ng kgÿ1). The highest value (sample E1)has certainly been in¯uenced by materials comingfrom the most polluted industrial canals;

3. Sediments of canals of the 1st Industrial Area, es-pecially those of the Nord Industrial Canal, pres-ently represent the potentially most dangeroussource of pollutants within the lagoon system inthat they can be resuspended by dredging opera-tions or by the passage of ships;

4. Three di�erent pro®les of PCDD/Fs can be foundin sediments. One represents the OCDD compo-nent of the atmospheric input, mainly due to com-bustion. Other sources are untreated domesticsewages and boat exhausts. The second is foundonly in the Brentelle Canal, and is mostly derivedfrom both the concentration of atmospheric con-taminants, due to the production of liquid gases,and the runo� of 170 ha of industrial land. Thethird has an uncertain origin, but the materialhas been probably produced by factories locatedin the 1st Industrial Area and discharged into theBrentella Canal through a direct out¯ow.

5. A cluster analysis clearly separates these pro®lesand the sites subject to their in¯uence. It is shownthat pollution coming from the 1st Industrial Area

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is widely distributed over the lagoon, except in theBrentelle Canal, and that sediments of the town ofVenice and salt marsh M1 have been in¯uencedprincipally by OCDD;

6. Atmospheric inputs deliver to lagoon sedimentsmostly OCDD from urban areas and furans fromindustrial activities. Present ¯uxes are very lowand the urban contributions prevail close to thetown of Venice.

This study was funded by EniChem SpA through the Stabilimento diP.to Marghera. The authors wish to thank the members of the Envi-ronment Division of the Istituto per lo Studio della Dinamica delleGrandi Masse (CNR, Venezia), in particular R. Zonta, L. Zaggia andF. Costa assisted in choosing the lagoon sampling sites, and F. Si-mionato, R. Ruggeri and G. Zamperoni provided their support duringsampling operations. M. Mengoli and G. Rovatti carried out grain sizeand OC analyses, respectively. A particular role was played by G.Pompa through the continuous discussion of the di�erent aspects ofthe research. This is contribution n. 1173 of the Istituto per la GeologiaMarina, Consiglio Nazionale delle Ricerche, Bologna.

Bellucci, L. G., Frignani, M., Cochran J. K. and Cecconi, R. (1999)Atmospheric ¯uxes of toxic metals and environmental changes inthe Venice Lagoon as recorded by salt marshes. In Proceedings ofthe VI Symposium on Biogeochemistry of Wetlans, Fort Lauder-dale, Florida, July 11±14, 1999.

Cleverly, D., Schaum, J., Schweer, G., Becker, J. and Winters, D.(1997) The congener pro®les of anthropogenic sources of chlori-nated dibenzo-p-dioxins and chlorinated dibenzofurans in theUnited States. Organohalogen Compound 32, 430±435.

Cossu, R. and de Fraja Frangipane, E. (1986) Stato delle conoscenzesull'inquinamento della laguna di Venezia. Consorzio VeneziaNuova, Servizio Informativo, Venezia, 4 volumes.

Dannenberg, D., Andersson, R. and Rappe C. (1997) Levels andpatterns of polychlorinated dibenzo-p-dioxins, dibenzofurans andbiphenyls in surface sediments from the western Baltic Sea (ArkonaBasin) and the Oder River estuarine system. Marine PollutionBulletin 34, 1016±1024.

di Domenico, A., Turrio Baldassarri, L., Ziemaki, G., De Felip, E., LaRocca,C., Ferrari,G.,Cardelli,M., Volpi, F., Ferri, F., Iacovella,N.,Lupi, C., Rodriguez, F., DÕAgostino, O., Sansoni, R. and Settimo,G.(1998) Priority microcontaminants in sediment samples from theVenice Lagoon: a selection of concentration data and predominantanalytical features. Organohalogen Compound 39, 205±210.

Evers, E. G. H., van Berghem, J. W. and Olie, K. (1989) Exploratorydata analysis of PCDD and PCDF measurements in sediments fromindustrial areas. Chemosphere 19, 459±466.

Fattore, E., Benfenati, E., Mariani, G., Fanelli, R. and Evers, E. H. G.(1997) Patterns and sources of polychlorinated dibenzo-p-dioxinsand dibenzofurans in sediments from the Venice Lagoon, Italy.Environmental Science and Technology 31, 1777±1784.

Frignani, M., Bellucci, L. G., Paolucci, D. and Ravanelli, M. (1998)Distribution of heavy metals in sediments of the Venice Lagoon: therole of the industrial area. International Symposium on MarinePollution (Monaco, 5±9 October 1998), Extended Synopses, 264.

Hagenmaier, H., Lindig, C. and She, J. (1994) Correlation ofenvironmental occurrence polychlorinated dibenzo-p-dioxins anddibenzofurans with possible sources. Chemosphere 29, 2163±2174.

Jimenez, B., Hernandez, L. M., Gonzales M. J., Eljarrat, E., Rivera, J.and Fossi, M. C. (1998) Congener speci®c analysis of polychlori-nated dibenzo-p-dioxins and dibenzofurans in crabs and sedimentsfrom the Venice and Orgetello Lagoons, Italy. EnvironmentalScience and Technology 32, 3853±3861.

Lohse, J. (1991) Distribution of organochlorine pollutants in NorthSea sediments. Water Science Technology 24, 107±113.

Marcomini, A., Zanette, M., DÕAndrea, F. and Della Sala, S. (1997)Diossine, ambiente e salute. Arsenale Editrice, Venezia, 102 pp.

Norwood, C. B., Hackett, M., Pruell, R. J., Butterworth, B. C.,Williamson, K. J. and Naumann, S. M. (1989) Polychlorinateddibenzo-p-dioxins and dibenzofurans in selected estuarine sedi-ments. Chemosphere 18, 553±560.

Fig. 5 Dendrogram from a cluster analysis of homologue pro®les insediments of industrial canals, lagoon sediments and saltmarshes. Lower linkage distances mean higher similarities. 1, 2and 3 refer to the three di�erent pro®les described in the text.

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Oheme, M., Mano, S., Brevik, E. M. and Knutzen, J. (1989)Determination of polychlorinated dibenzofurans (PCDF) anddibenzo-p-dioxin (PCDD) levels and isomer patterns in ®sh,crustacea, mussel, and sediment samples from a fjord regionpolluted by Mg-pollution. Journal of Fresenius and Journal ofAnalytical Chemistry 335, 987±997.

Pavoni, B., Donazzolo, R., Marcomini, A., Degobbis, D. and Orio, A.(1987) Historical development of the Venice Lagoon contaminationas recorded in radiodated sediment cores. Marine Pollution Bulletin18, 18±24.

Ramacci, L., Ferrari, G. and Bonamin V. (1998) Sources of PCDDs/PCDFs from industrial and municipal waste water discharges andtheir spatial and temporal distribution in the sediments of theVenice Lagoon. Organohalogen Compound 33, 91±95.

Sfriso, A., Marcomini, A. and Zanette M. (1995) Heavy metals insediments, SPM and phytozoobenthos of the Lagoon of Venice.Marine Pollution Bulletin 30, 116±124.

Stringer, R. L., Costner, P. and Johnston, P. A. (1995) PVCmanifacture as a source of PCDD/Fs. Organohalogen Compound24, 119±123.

Swerev, M. and Ballschmiter, K. (1989) Pattern analysis of PCDDsand PCDFs in environmental samples as an approach to anoccurrence source correlation. Chemosphere 18, 609±616.

Turrio Baldassarri, L., di Domenico, A., Iacovella, N., La Rocca, C.and Rodriguez, F. (1994) PCDD and PCDF contamination ofsediments from the Venice Lagoon. Organohalogen Compound 20,183±186.

Tyler, A. O. and Millward, G. E. (1996) Distribution and partitioningof polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofur-ans and polychlorinated biphenyls in the Humber Estuary, UK.Marine Pollution Bulletin 32, 397±403.

US Environmental Protection Agency. (1989) Interim procedures forestimating risk associated with exposures to mixtures of chlorinateddibenzo-p-dioxins and dibenzofurans (CDDs and CDFs) and 1989upgrade. US EPA, Risk Assessment Forum, Washington DC; EPA/625/3±89/016.

Wenning, R. J., Harris, M. A., Ungs, M. J., Paustenbach, D. J. andBedbury, H. (1992) Chemometric comparison of polychlorinateddibenzo-p-dioxin and dibenzofuran residues in sur®cial sedimentsfrom Newark Bay, New Jersey and other industrial waterways,Archieves of Environmental and Contamination Toxicology 22, 397±413.

Zonta, R., Costa, F., Ghermandi, G., Pini, R., Perin, G., Traverso, P.,Vazzoler, S. and Argese, E. (1992) Geochemical and chemical-phisical characterization of a pollutedmud ¯at in the Venice Lagoon.Bulletin of the Institute of the Oceanography, Monaco 11, 207±226.

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