Introduction

Estuarine systems are of key importance for the removalof suspended matter and associated pollutants from thenatural water cycle. Their environmental significancehas made them the subject of considerable scientificinterest over the last decades. Sediments in coastal sys-tems, which are surrounded by urbanized and industri-alized areas may contain high quantities of heavy metals,which are highly phytotoxic and can affect the biologicalprocesses of the coastal environment. Guanabara Bay isone of the most prominent coastal bays in Brazil(Fig. 1). The bay is an estuary of 91 rivers and channels,surrounded by the cities of Rio de Janeiro, Duque deCaxias, Sao Goncalo, Niteroi and many other smallcities and villages. The bay receives considerableamounts of contaminants introduced from sewageeffluents, industrial discharge, urban and agricultural

runoff, atmospheric fallout, and the combined inputsfrom the rivers. The bay also hosts two airports, holdsone of the countries main naval estates and is crossed bya 12 km long bridge used by thousands of cars daily.

Guanabara Bay has been identified as one of themain polluted coastal environments on the Braziliancoastline, and recently it experienced an environmentaldisaster, when on 18th January 2000, approximately1,300 m3 of marine fuel oil were spilled into the bay as aconsequence of a pipeline rupture at one of the refiner-ies. Previous studies of heavy metal pollution inGuanabara Bay are from the early 1980s (Rebello et al.1986) or concentrate on single sites or metal species inthe bay (Vandenberg and Rebello 1986; Leal and Wa-gener 1993; Barrocas and Wasserman 1995; BaptistaNeto et al. 2000; Faria and Sanches 2001).

The aim of this work is a comprehensive survey of theheavy metal concentrations and distributions in the

Jose Antonio Baptista Neto

Franz Xaver Gingele

Thomas Leipe

Isa Brehme

Spatial distribution of heavy metalsin surficial sediments from GuanabaraBay: Rio de Janeiro, Brazil

Received: 16 May 2005Accepted: 15 November 2005Published online: 1 March 2006� Springer-Verlag 2006

Abstract Ninety-two surface sedi-ment samples were collected inGuanabara Bay, one of the mostprominent urban bays in SE Brazil,to investigate the spatial distributionof anthropogenic pollutants. Theconcentrations of heavy metals, or-ganic carbon and particle size wereexamined in all samples. Large spa-tial variations of heavy metals andparticle size were observed. Thehighest concentrations of heavymetals were found in the muddysediments from the north westernregion of the bay near the mainoutlets of the most polluted rivers,municipal waste drainage systemsand one of the major oil refineries.Another anomalous concentration

of metals was found adjacent to Riode Janeiro Harbour. The heavy me-tal concentrations decrease to thenortheast, due to intact rivers andthe mangrove systems in this area,and to the south where the sandfraction and open-marine processesdominate. The geochemical normal-ization of metal data to Li or Al hasalso demonstrated that the anthro-pogenic input of heavy metals havealtered the natural sediment heavymetal distribution.

Keywords Heavy metals Æ Coastalenvironment Æ Normalization ÆMarine sediments Æ Brazil

Environ Geol (2006) 49: 1051–1063DOI 10.1007/s00254-005-0149-1 ORIGINAL ARTICLE

J. A. B. Neto Æ I. BrehmeDepartamento de Geologia, UniversidadeFederal Fluminense, Av. Litoranea s/n,Gragoata, Niteroi, CEP 24210-340 Rio deJaneiro, Brazil

J. A. B. Neto (&)Departamento de Geografia, FFP/Universidade do Estado do Rio de Janeiro,Rio de Janeiro, BrazilE-mail: jneto@igeo.uff.brTel.: +55-21-26295917Fax: +55-21-26295931

F. X. Gingele Æ T. LeipeInstitut fur Ostseeforschung, Warnemunde(IOW), University of Rostock,Rostock, Germany

whole of Guanabara Bay surficial sediments to deter-mine the extent of pollution in the bay. The concentra-tions of heavy metals are also normalized using Al andLi as conservative elements. Additionally, the enrich-ment factors (EF) and the geoaccumulation index (Igeo)are estimated for the elements analysed.

Environmental setting

Guanabara Bay is in Rio de Janeiro State—SoutheastBrazil, between 22�40¢ and 23�00¢S of latitude and043�00¢–043�18¢W longitude. It is one of the largest bayson the Brazilian coastline and has an area of approxi-mately 384 km2, including it islands. According toAmador (1980) the coastline of the bay is 131 km long;the mean water volume is 1.87·109 m3. The bay mea-sures 28 km from west to east and 30 km from south tonorth, but the narrow entrance to Guanabara Bay isonly 1.6 km wide (Kjerfve et al. 1997). Guanabara Bayhas a complex bathymetry with a relatively flat centralchannel. The channel is 400 m wide, stretches from themouth more than 5 km into the bay, and is defined bythe 30 m isobath. The deepest point of the bay measures58 m and is located within this channel (Kjerfve et al.1997). According to the same authors, north of Rio deJaneiro-Niteroi bridge, the channel loses its character-istics as the bay rapidly becomes shallower, with anaverage depth of 5.7 m, due to the high rates of sedi-mentation, accelerated in the past century by anthro-pogenic activities in the catchment area.

Guanabara Bay lies within the tropics of southeastern Brazil, but because of its coastal location ahumid sub-tropical climate with 2,500 mm (high alti-tudes) and 1,500 mm (low altitudes) of rainfall prevailsbetween December and April. The mean annual tem-perature is between 20 and 25�C (Nimer 1989). Thedrainage basin of Guanabara Bay has an area of4,080 km2, consists of 32 separate sub-watersheds(Kjerfve et al. 1997). However, only six of the rivers areresponsible for 85% (JICA 1994) of the 100 m3 s)1 ofthe total mean annual freshwater input. Nowadays, 11million inhabitants live in the greater Rio de Janeirometropolitan area, which discharges tons of untreatedsewage directly into the bay. The second largestindustrial site of Brazil is found in this area. There aremore than 12,000 industries in the drainage basinwhich account for 25% of the organic pollution re-leased to the Bay (FEEMA 1990). The bay also hoststwo oil refineries along its shore, which processes 7%of the national oil. At least 2,000 commercial shipsdock in the port of Rio de Janeiro every year, makingit the second biggest harbour in Brazil. The bay is alsothe home port to two naval bases, a shipyard, and alarge number of ferries, fishing boats, and yachts(Kjerfve et al. 1997).

In the last 100 years the catchment area aroundGuanabara Bay has been strongly modified by humanactivities, in particular deforestation and uncontrolledsettlement, which increased river flow velocities andsediment load and transport to the bay. Consequentlythe average rates of sedimentation has increased to1–2 cm year)1 (Godoy et al. 1998).

Methodology

Sampling

Surface sediments were collected in November 1999 witha Van veen grab sampler at 92 stations (Fig. 1), pro-viding an almost complete geographic coverage of thebay area. The exact position of each sample was re-corded using Global Position System (GPS). The sedi-ment was carefully removed from the middle of thesediment sampler, using a plastic spatula. To avoidmetal contamination, the samples were placed in a PVCcontainer and kept frozen until analysis.

Analyses

Granulometric analyses were carried out using standardsieve and pipette techniques after organic matterdestruction with H2O2 (Folk 1974). The total organiccarbon, inorganic carbon and S contents were deter-mined using an CS infrared analyser model Eltra Met-alyt 1000CS. The metals were determined by totaldigestion of the sample in HF/HClO3 and analysis withan ICP-AES.

Results and discussion

Particle size and organic matter

The estuarine and bay environments are influenced bycontinental and marine factors. The sediment, in gen-eral, is a combination of minerals and organic detritus,the characteristics of which vary according to the depthand distance from the mouth of the rivers or the en-trance of the bay. Variations in the size characteristicsof the different sediment types are directly related towater movement patterns (tidal and wave-energy re-gimes). Guanabara Bay is a typical low energy, micro-tidal estuarine environment that can be separated intothree zones: an external zone affected by wave actionand tidal currents, an inner zone characterized by verylow energy, and a transitional zone characterized by amix of sediments. The bottom sediments of theGuanabara Bay vary from clay to coarse sand. Theparticle sizes vary from 0 to 100% sand, 0 to 92% silt

1052

Fig. 1 The location map of the studied area with the position of the surficial samples

1053

and 0 to 85% clay. Near the entrance of the bay in themain channel, the sediments are classified mainly ascoarse to very fine sand (Fig. 2). This area is subject tointense hydrodynamic action from waves and tidalcurrents, indicated by the presence of sandwaves.According to Quaresma et al. (2000) and Kjerfve et al.(1997) these sandwaves occur along the eastern marginof the central channel between the 10 and 6 m isobathsbetween Morro do Morcego and Gragoata. These sandwaves have heights of 0.5–2.5 m, lengths of 18–98 m,and decrease in both height and wavelength from theocean into the bay in response to decreasing tidal en-ergy. The sandwaves have steeper slopes facing the bay,indicating wave progression and bottom sand transportinto Guanabara Bay. The sandwaves and their char-acteristics results from energetic ocean swells associatedwith meteorological frontal passages and the tidalflood-dominance of bottom current. From the align-ment of Forte Gragoata and Aeroporto Santos Du-mont, the bay widens in the main channel, whichreflected in a reduction of the current speeds, increasingdeposition of fine sediments in both sides of thechannel. Sediments are primarily clayed-silt and silt-clays deposited as a function of the SSW waves and thetidal current. In this area the organic carbon concen-tration is very low, with less than 2% (Fig. 3). Thenorth and the centre of the bay are characterized by thepresence of muddy sediments. These areas are pro-tected from wave and tidal current actions, and havevery low hydrodynamic energy, accumulating sedi-ments mainly silt and clay. In this part of the bay theorganic carbon in the sediment varies from 4 to morethan 6%, resulting from the high productivity of itswater and also from the great amount of untreatedsewage entering the bay. According to Carreira et al.(2002) the bay is amongst the most productive carbonmarine ecosystems, with an average net primary pro-duction (NPP) of 0.17 mol C m)2 day)1 (Rebello et al.1986). According to the same authors the high pro-ductivity is sustained by the abundant availability ofintensive sunlight and elevated temperature throughoutthe year and by an estimated annual input of3.2·109 mol P and 6.2·1010 mol N, which is (Wagener1995) delivered mainly by untreated sewage.

Spatial distribution of heavy metals in Guanabara Baysediments

The map of heavy metals concentrations (Fig. 4) showsconsistent regional distribution patterns with a strongcorrelation to particle size and organic carbon content.The lowest concentrations of heavy metals are found inthe southern area of the bay near the entrance, and thehighest concentrations in the northwest part of the bay,which is dominated by organic—muddy sediments.

Along with particle size distribution and hydrody-namics, the proximity of contaminant sources plays animportant role in the distribution of the heavy metalconcentrations in the Guanabara Bay surface sediments.The concentration of heavy metals increases towards tothe northwest area of the bay as compared to thenortheast. Both areas have the same type of sedimentand organic carbon content (Figs. 3, 4). However, thenorth western area shows the highest concentrations ofheavy metals, due to the discharge of the most pollutedrivers in this area, and also the location of a large oilrefinery. Additionally, the north eastern part of the bayis a protected environmental area abounding withmangrove and is relatively intact. The rivers in this areaalso show a better water quality, and are relatively cleancompared to the rivers which flow to the rest of the bay.

Two other hot spots of heavy metal concentrationoccur; one is the Rio de Janeiro Harbour, which showsthe second highest concentration of heavy metals in thebay. Dockyards and harbour areas have been describedin the international literature as typical locations wheresediment-associated pollutants can accumulate. Studiescarried out by Baptista Neto et al. (2005) and Vilelaet al. (2004) on the concentration and bioavailability ofheavy metals in the Niteroi Harbour, located in theNiteroi coastline, show high concentrations of heavymetals. The other hot spot is Jurujuba Sound, whichaccording to previous work (Baptista Neto et al. 2000),is considered to be one of the most polluted sites inGuanabara Bay due to sewage pollution. Only Pb showsanother conspicuous hot spot located in the central partof the Bay (Fig. 4). In this area there is an oil terminaland the affinity of Pb to oil activities could explain in-creased concentrations.

Concentrations of the heavy metals show a widerange of values. The element, which shows the widestvariation is Zn (Fig. 4), ranging between 5 ppm in thesandy sediments adjacent to the entrance of the bay to755 ppm in the muddy sediments of the north westernpart of the bay. The latter value is 12.9 times higher thanthe preanthropogenic background level of trace elementsin muddy sediments from the base of cores collected inJurujuba Sound (Baptista Neto et al. 2000), and 7.9higher than the average shale (Turekian and Wedepohl1961) (Table 1). In small amounts zinc is an essentialelement for terrestrial life and is required as a structuralcomponent in numerous enzyme systems (Nriagu 1989).Zn is also associated, however, with sewage pollution(Muniz et al. 2003).

Cu also shows elevated values (Fig. 4), which rangefrom 2 ppm in the sandy sediments to 88 ppm in themuddy sediments. The maximum concentration is 20.8times higher than the preanthropogenic background,and 4.2 times higher than the average shale (Table 1).Cu in small amounts is also essential for biologicalprocesses. Cu may be associated with sewage contami-

1054

nation, however, and shows a high affinity for humicsubstances, which represent a major component of theorganic matter in recent sediments (Calvert et al. 1985).

The highest concentrations of Pb (Fig. 4) (193 ppm)are found in Rio de Janeiro Harbour and the lowestconcentrations in the main channel of the bay (2 ppm).

Fig. 2 Map of particle size distribution of surface sediments from Guanabara Bay

1055

The highest values are 7.9 times higher than the prean-thropogenic background (24.4 ppm) (Table 1). Pb hasno known biological function; and its effects on bio-

logical communities can be very harmful (Kennish1992). According to Abrahim and Parker (2002) almost95% of lead emitted to the environment is associated

Fig. 3 Map of the organic matter (%) distribution in Guanabara Bay surface sediments

1056

with human activity, and studies show that lead con-centration as low as 0.2 ppm may cause adverse effectsin aquatic biota (Wong et al. 1978).

Cr also shows high concentrations in Guanabara Baysediments (Fig. 4), ranging from 2 ppm in the sand to413 ppm at the mouth of one of the most polluted rivers

Fig. 4 The element Zn, Cu, Pb,Cr and Ni (ppm) distribution inthe <63 lm size fraction ofGuanabara Bay surface sedi-ments

1057

Table

1Concentrationsofheavymetalsin

thestudyarea(m

inim

um

-maxim

um)(average),comparedwithvalues

from

theliterature

Location

Pb(ppm)

Zn(ppm)

Cu(ppm)

Cr(ppm)

Ni(ppm)

Co(ppm)

Li(ppm)

Al(ppm)

Fe(ppm)

References

Guanabara

Bay

2–19340

5–755149

2–18840

2–41364

1–3515.5

1–209

2–6234

0.6–9245

Thisstudy

Backgrounda

24.4

58.4

940.5

27

19

63

21,775

BaptistaNetoet

al.(2000)

SepetibaBay

6.5–83

18.1–795

2.1–166

23.7–121

––

––

123–788

Lacerdaet

al.(1987)

TaylorSlough(Everglades)

29–150

76–718

31–220

96–807

51–238

0–34

–85–777

75–233

Goughet

al.(1996)

GulfofCarpentaria,Australia

1–136

5–7920

1–105

3–4712

0–66

0–73

––

–CoxandPreda(2003)

FloridaBay,USA

1.9–25.8

9–61

6.4–32

57–347

4.9–54

1–9.6

–4–120

6.2–63

Gonzalez-Caccia

(2002)

Ganges

Estuary,India

12–115

12–611

4–53

21–100

8–57

––

–12,000–46,000

Subramanianet

al.(1988)

PosajesPort,Spain

45–346

477–1.390

25–372

–17–99

––

–4,000–40,000

Legorburu

andCoanton(1991)

Averageshale

20

95

45

90

68

35,900

TurekianandWedepohl(1961)

Worldssurface

rock

16

127

32

71

49

––

693

47,000

Martin

andMeybeck(1979)

aLevel

oftrace

elem

ents

inmudsedim

ents

from

thebase

ofadatedcore

collectedin

JurujubaSound-G

uanabara

Bay

Table

2Pearsoncorrelationcoeffi

cientmatrix

forheavymetalsin

thesurface

sedim

ents

from

Guanabara

Bay

TOC

(%)

Al

(%)

Li

(ppm)

Fe

(%)

Mn

(ppm)

Ca

(%)

TIC

(%)

P (ppm)

K (%)

S (%)

Mg

(%)

Zn

(ppm)

Cu

(ppm)

Pb

(ppm)

Ni

(ppm)

Cr

(ppm)

Co

(ppm)

Mud

(%)

TOC

(%)

1.000

Al(%

)0.816

1.000

Li(ppm)

0.713

0.877

1.000

Fe(%

)0.764

0.770

0.798

1.000

Mn(ppm)

0.517

0.570

0.654

0.598

1.000

Ca(%

)0.065

0.013

-0.109

)0.247

)0.155

1.000

TIC

(%)

0.263

0.190

0.216

0.240

0.101

0.197

1.000

P(ppm)

0.859

0.752

0.674

0.706

0.563

0.022

0.161

1.000

K(%

)0.384

0.411

0.347

0.126

0.039

0.423

0.082

0.439

1.000

S(%

)0.760

0.824

0.832

0.847

0.609

-0.254

0.244

0.680

0.142

1.000

Mg(%

)0.725

0.798

0.754

0.557

0.577

0.105

0.137

0.701

0.499

0.698

1.000

Zn(ppm)

0.786

0.672

0.573

0.608

0.415

0.027

0.105

0.836

0.493

0.641

0.714

1.000

Cu(ppm)

0.750

0.721

0.659

0.670

0.490

-0.116

0.073

0.764

0.401

0.724

0.726

0.909

1.000

Pb(ppm)

0.669

0.633

0.590

0.564

0.605

0.016

0.149

0.639

0.358

0.608

0.677

0.799

0.812

1.000

Ni(ppm)

0.750

0.757

0.772

0.744

0.606

-0.098

0.263

0.779

0.337

0.782

0.741

0.715

0.752

0.715

1.000

Cr(ppm)

0.699

0.730

0.650

0.689

0.435

-0.116

0.148

0.745

0.339

0.693

0.672

0.814

0.807

0.642

0.726

1.000

Co(ppm)

0.725

0.748

0.782

0.898

0.603

-0.362

0.175

0.728

0.191

0.810

0.516

0.617

0.702

0.596

0.764

0.677

1.000

Mud(%

)0.802

0.805

0.805

0.713

0.609

0.031

0.030

0.713

0.162

0.678

0.299

0.672

0.633

0.511

0.924

0.545

0.917

1.000

1058

in Guanabara Bay, Iguacu River. This river drains anurban area, and in a previous study dealing with metalsfrom urban street runoff (Baptista Neto et al. 1999) theauthors suggested that one of the main sources of Cr inurban area is the wearing of vehicle parts, such as en-gines, tires and oil. The same authors also found highconcentrations of Cr near the dockyards. The highestvalues of Cr at this location are ten times higher than theaverage preanthropogenic background.

Ni shows a fairly homogeneous low concentration inthe study area (Fig. 4), ranging from 1 to 35 ppm. Theaverage concentration is 15.5 ppm and the values for thepreanthropogenic background is 27 ppm. The concen-tration of Ni in the study area is also lower than theaverage shale (68 ppm) and the world surface rock(49 ppm) (Martin and Meybeck 1979). Ferromanganeseminerals and ferrous sulphides are among the naturalsources of this element (Muniz et al. 2003).

A comparison of trace metal concentrations foundin the study area with those reported for other coastalareas around the world (Table 1), the concentrations ofpreanthropogenic background from the area, theaverage shale (Turekian and Wedepohl 1961) and theworld surface rock (Martin and Meybeck 1979), showsthat in the Guanabara Bay sediments, metal concen-tration can be considered highly enriched for Pb, Zn,Cu and Cr. Compared to the natural concentrationsand to other coastal areas around the world, only thePosajes Port-Spain study (Legorburu and Coanton1991) and Taylor Slough (Everglades) (Gough et al.1996) shows higher concentrations than GuanabaraBay.

Correlation coefficients

The degree of correlation between trace metals andother major constituents is often used to indicate theorigin of the metals (Windom et al. 1989). Previousstudies have demonstrated that grain size is a majorfactor in controlling sedimentary heavy metal concen-trations (Windom et al. 1989; Baptista Neto et al. 2000;Lin et al. 2002; Huang and Lin 2003). Strong positivecorrelation coefficients of all the metals and the organiccarbon with the mud (silt and clay) content of thesediments were found (Table 2), suggesting that thehighest metal and organic carbon concentrations areassociated with the fine-grained sediments of the studyarea, as these components are more readily adsorbedon clay minerals. Significant and positive correlationcoefficients were also observed between organic carbonand the trace elements, suggesting their commonaccumulation into the fine-grained fraction of the sed-iments. However, mud and organic carbon contents inthe surface sediments are themselves correlated(r=0.802), as organic components adhere to clay

minerals as well. Their combined importance as ageochemical substrate for heavy metal concentrations issignificant for these sediments.

Correlation analysis also reveals close relationshipsbetween individual elements, which suggest that simi-lar processes governed the behaviour of all metals.This strong degree of association between the mainmetals (Cu, Pb, Zn, Ni and Cr) was also reported inthe literature for different urbanised and pollutedareas (Ruiz 2001; Spencer 2002; Muniz et al. 2003).However, when the correlation data are comparedwith metal distribution it is possible to observe thatmetal concentration are much more influenced by thesource areas than the organic matter or particle size.As stated before.

Normalisation of the geochemical data

The heavy metal variability of sediments may be naturalor influenced by anthropogenic sources. According toMecray and Brink (2000) the concentration of metals insediments is dependent on the amount added by humanactivities, the amount naturally present, and the capacityof the sediment to absorb or sequester metals introducedto the system. To reduce grain size and mineralogicaleffects on metal variability, and to identify possibleanomalous metal concentrations, geochemical normali-sation of the heavy metal data to a conservative element,should be applied. Several conservative elements havebeen used for normalisation purposes: Al (Balls et al.1997; Huang and Lin 2003); Li (Aloupi and Angelidis2001; Soto-Jimenez and Paez-Osuna 2001); Cs (Ack-eman 1980); Sc (Grousset et al. 1995) and Fe (Rule 1986;Baptista Neto et al. 2000). This procedure indicatesmetal enrichment factors (EF). The EFs for each ele-ment were calculated from the formulae (Salomons andForstner 1984):

EF¼(metal/AlorLi)sample from the study area sediments

(metal/AlorLi)Background

Metal concentrations in the basal muds collected fromJurujuba Sound (Baptista Neto et al. 2000) located in-side of the bay were used as the preanthropogenicbaseline levels for the study area and are assumed to givea common reference point for comparisons. EFs around1.0 indicate that the element in the sediment is originatedpredominantly from lithogenous material, whereas EFsgreater than 1.0 indicate that the element is of anthro-pogenic origin (Szefer et al. 1996).

Figures 5 and 6 presents the EFs for the studiedmetals and shows that the areas with the highest valuesare the Rio de Janeiro Harbour and the northwest areaof the Bay, close to the outlet of the main polluted riversand one of the oil refineries. In general, calculated EFs

1059

were highest for Zn, Cu, Pb and Cr. EFs for Ni and Cowere similar to or less than background levels. Thehighest EF values (19.9 for Zn, 18 for Cu, 5.8 for Pb and

7.7 for Cr) demonstrated that the sewage drainage andthe oil refinery are the main sources of heavy metalpollution in the area.

Fig. 5 Enrichment factors (EF) distribution for the metals in Guanabara Bay surface sediments (<63 lm) using Li as a conservativeelement compared with the cores basal muds

1060

Conclusions

Guanabara Bay is within the second biggest urban areaof Brazil, which makes it subject to intense anthropo-

genic activities and consequently affects the quality ofthe bottom sediments of Guanabara Bay.

A large spatial variation of heavy metals contami-nation in the surface sediments of Guanabara Bay can

Fig. 6 Enrichment factors (EF)distribution for the metals inGuanabara Bay surface sedi-ments (<63 lm) using Al as aconservative element comparedwith the cores basal muds

1061

be related to large-scale differences in the particle size,organic carbon content, water dynamics, and mostimportantly, the anthropogenic influence. The pollutionproblem in Guanabara Bay has been increasing over thelast few decades. The disposal of industrial, urban andrecreational wastes, atmospheric fallout, the combinedinputs from rivers and the naval activities have all con-tributed.

Guanabara Bay can be divided into four regions withdifferent degrees of environmental pollution; the northwestern area of the bay and Rio de Janeiro Harbourarea show the highest concentrations of heavy metals.The outlets of the most polluted rivers in GuanabaraBay are in these two areas, as in one of the oil refineries.In the harbour, heavy metal concentrations are associ-ated with naval activities and the outlet of one of themost polluted river in the catchment. The north easternarea, which is semi-enclosed, shows better environmen-tal conditions due to the preservation of the mangroveswamps on the coast. Lower concentrations of heavymetals are found in this area as compared to the northwestern semi-enclosed area. The third area is in the en-trance of Guanabara Bay, which is affected by strongwater exchange processes, with sandy sediments andlower concentrations of organic carbon. This is due to

the sediment characteristics and regional environmentalconditions. Concentrations of heavy metals in this thirdarea are very low. The fourth and final area is thetransitional zone between the tree areas and shows arange of value from highest to lowest.

When comparing levels ofheavy metals in the studiedarea to other coastal areas, the levels of Cu, Zn, Pb andCr content are higher than in many other areas and alsoshow a strong enrichment compared to the prean-thropogenic background levels.

The correlation coefficients for relationships betweenthe metals shows a strong degree of association betweenthe main metals, similar to other polluted and urbanisedcoastal environments around the world. The normali-zation of the data also shows that the Guanabara Bay issubject to severe pollution, particularly with regard toZn, Pb, Cu and Cr.

Acknowledgements Funding for this project was provided througha cooperation programme funded by the ‘‘Internationales BuroNord-und Sudamerika des BMBF (Germany; BRA99/036MAR)’’and a research grant from FAPERJ (Rio de Janeiro State ScienceFoundation) and CNPq (Brazilian Science Foundation). Thewriters are also indebted to Dr. Cleverson G. Silva for fieldworkassistance and the MSc students from Departamento de GeologiaUFF for their help during the fieldwork.

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Amador ES (1980) Assoreamento da Baıade Guanabara—taxas de sedimentacao.An Acad Bras Cienc 52(4):723–742

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