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Marine Pollution Bulletin

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Chronology of anthropogenic impacts reconstructed from sediment recordsof trace metals and Pb isotopes in Todos os Santos Bay (NE Brazil)

R.L.B. Andradea,⁎, V. Hatjea, P. Masquéb,c,d, C.M. Zurbricke, E.A. Boylee, W.P.C. Santosf

a Centro Interdisciplinar de Energia e Ambiente (CIENAM), Instituto de Química, Universidade Federal da Bahia, Rua Barão de Jeremoabo, s/n, Ondina, Salvador, BA40170-290, Brazilb Centre for Marine Ecosystems Research, School of Science, Edith Cowan University, Joondalup, WA 6027, Australiac Institut de Ciència i Tecnologia Ambientals, Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spaind Oceans Institute & School of Physics, The University of Western Australia, Crawley, WA 6009, Australiae Earth, Atmospheric, and Planetary Sciences (EAPS), Massachusetts Institute of Technology, Cambridge, MA 02139, USAf Departamento de Química (DAQ-SSA), Instituto Federal da Bahia, Salvador, BA 40301-015, Brazil

A R T I C L E I N F O

Keywords:ContaminationSediment pollution recordTrace elementsPb isotopesSedimentation ratesTodos os Santos Bay

A B S T R A C T

The evolution of the impacts of anthropogenic activities in Todos os Santos Bay was evaluated by profiles of tracemetals and Pb isotopes determined in sediment cores. Fluxes of metals increased up to 12, 4 and 2 times for Cu,Pb, and Zn, respectively, compared to those recorded in the beginning of the 20th century. Stable Pb isotopesidentified a decommissioned lead smelter and burning of fossil fuels as the main sources of Pb. Most metalsshowed minor to moderate enrichment factors (EF < 4), but Cu and Pb were highly enriched (EF = 28 and 6,respectively) at the Aratu harbor. Temporal changes in sediments were associated to different activities, namelyPb smelting, burning of fossil fuels, maritime traffic, petroleum related activities, inputs of domestic effluents,and changes in land uses. The effects of the implementation of environmental policies to improve the waters ofthe bay could not be identified in the evaluated cores.

1. Introduction

The world's population growth - associated with industrial andtechnological development, the massive exploitation of natural re-sources, intensive agriculture practices, production of new materials(e.g. plastics), the extinction of species and the proliferation of exoticspecies in several places - have supported the designation ofAnthropocene for the current geological epoch (Crutzen and Stoermer,2000; Waters et al., 2014, 2016). During this period, anthropogenicactivities started to exert dominance over many geological surfaceprocesses, substantially increasing the scale of human negative impactson the planet's environment (Halpern et al., 2008; Meybeck, 2003). As aresult, anthropogenic fluxes of trace metals to water bodies, which canact as contaminants, increased substantially, perturbing their globalbiogeochemical cycles (Boyle et al., 2014; Nriagu, 1993; Pacyna andPacyna, 2001).

The coastal zone is particularly relevant in this scenario because itprovides space, goods, and services to human beings and highly diversehabitats to organisms. This region is heavily populated and in-dustrialized, being extremely vulnerable to man-made changes to soil,atmosphere and waters both in local and global scales (Jennerjahn,

2012). Coastal systems receive most of the fluvial inputs of water, aswell as dissolved and particulate matter (Martin and Meybeck, 1979;Milliman and Farnsworth, 2013; Viers et al., 2009). A major portion ofthe fluxes of the natural and anthropogenic materials introduced intocoastal systems tend to accumulate in sediments, leading to unequi-vocal geochemical signatures within sedimentary bodies, thus re-gistering changes in time (Bruland et al., 1974). These anthropogenicgeochemical signatures include elevated levels of contaminants such asmetals (Bai et al., 2016; Begy et al., 2016; Garcia-Orellana et al., 2011),polycyclic aromatic hydrocarbons (PAHs) (Martins et al., 2015; Penget al., 2008), pesticides (Alonso-Hernández et al., 2015; Kaiser et al.,2016), polychlorinated biphenyls (PCBs) (Combi et al., 2016; Ruiz-Fernández et al., 2012), in addition to changes in Pb isotopic compo-sition (Nriagu and Pacyna, 1988; Waters et al., 2016; Yu et al., 2016;Zhang et al., 2016).

The chronological history of environmental impacts can be assessedby dating sedimentary deposits (e.g., Birch et al., 2013; Ontiveros-Cuadras et al., 2014; Palanques et al., 1998). 210Pb (T1/2: 22.3 yr) is anaturally occurring radionuclide from the 238U series commonly used toobtain age models of recent (~100–150 years) deposits (Appleby andOldfield, 1978). Given that natural and anthropogenic processes may

http://dx.doi.org/10.1016/j.marpolbul.2017.07.053Received 26 April 2017; Received in revised form 19 June 2017; Accepted 22 July 2017

⁎ Corresponding author.E-mail address: raiza.lopes@ufba.br (R.L.B. Andrade).

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disturb the sedimentary record, the use of complementary tracers, suchas Pb isotopic compositions (Cheng and Hu, 2010) and/or artificialradionuclides (e.g., 137Cs) becomes important for the validation of the210Pb derived chronology (Smith, 2001).

Lead is a valuable geochemical tracer of contamination because ofits four naturally occurring stable isotopes: 206Pb, 207Pb, 208Pb, and204Pb. Though 204Pb abundance on Earth has not varied in time, theabundances of 206Pb, 207Pb, and 208Pb in an ore deposit depend onwhen the ore was formed, since they are products of radioactive decay.As Pb does not undergo significant isotopic fractionation in natural orindustrial physicochemical processes, the isotopic composition onlychanges if mixed with a secondary source of Pb (Ault et al., 1970). Sincedifferent sources of Pb may have distinct isotopic signatures, lead iso-topes are a suitable tool for tracing sources of Pb in different environ-mental compartments, as well as studying its transport pathways(Cheng and Hu, 2010; Graney et al., 1995; Komárek et al., 2008;Oulhote et al., 2011).

The Todos os Santos Bay (BTS), northeast Brazil (Fig. 1), is locatedin the vicinity of Salvador, the third largest metropolitan area in Brazil,with a population of 2.9 million (IBGE, 2016). The BTS, with its richand diverse environments, has ecological and historical socio-economicimportance. It houses commercial and subsistence fishing activities,

which supports traditional coastal populations. Since the constructionof the Landulpho Alves Refinery (RLAM) in the 1950s, the Bay hasexperienced a series of environmental pressures that impacted nega-tively the environmental quality, biodiversity and ecological services ofthe Bay (de Souza et al., 2011; Hatje et al., 2006, 2016; Hatje andBarros, 2012; Ribeiro et al., 2016). Nevertheless, the identification ofthe sources of contaminants and their changes along time, and thepotential effects of the application of environmental regulations andprotective measures are still largely unknown.

The objective of this study was to reconstruct the chronology ofcontamination by trace elements in the Todos os Santos Bay by in-vestigating the sedimentary record. Pb stable isotopes and trace ele-ment concentration profiles were used to constrain the importance andtemporal variation of diverse anthropogenic activities that had con-tributed to the contamination of the Bay.

2. Methods

2.1. Study area

The BTS, the second largest bay (1,223 km2) in Brazil, is considereda fluvial-marine depositional environment with tropical climate

Fig. 1. Location of cores (Cores CI1-CI5) and surface sediments (#3 and #9) sampled at the Todos os Santos Bay, Bahia. The locations of Enseada Indústria Naval Shipyard (EIN), SãoRoque do Paraguaçu Shipyard (CSRP), Pedra do Cavalo Dam (PC Dam), Landulfo Alves Refinery (RLAM), and Madre de Deus Harbor Terminal (TEMADRE) are shown.

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characteristics and diverse ecosystems (coral reefs, estuaries, man-groves, islands, and tidal flats) (Cirano and Lessa, 2007). In thenorthern section of the Bay, sediments are mostly composed of mud,while sand prevails in the southern section (Lessa and Dias, 2009). Thecurrents inside BTS are tidally driven and the tides are semidiurnal witha maximum range of 2.7 m (Lessa et al., 2001). Paraguaçu (56,300 km2)and, to a lesser extent, Jaguaripe (2200 km2), and Subaé (600 km2)rivers are the three major tributaries of the bay (Cirano and Lessa,2007). The Paraguaçu River has had its hydrological regime artificiallycontrolled since the construction of the Pedra do Cavalo dam (PC dam)in 1985. The average discharge of the Paraguaçu River was estimatedaround 91 m3 s−1 up to 1986 and dropped to around 64 m3 s−1

afterward (Cirano and Lessa, 2007).The construction of the RLAM in 1950s led to extensive industrial

growth in BTS, with the development of the Camaçari Industrial Center,the largest petrochemical complex of the southern hemisphere, and theAratu Industrial Complex (CIA), which houses industries from manysectors, e.g. chemical, metallurgy, cosmetic, beverages, among others(CRA, 2008). Since then, the anthropogenic pressures in BTS increasedprogressively and several activities have been influencing the en-vironmental quality of the Bay, such as terrestrial runoff, shrimpfarming, inputs of industrial and untreated domestic effluents, solidwastes, mining and intense harbor activities (Beretta et al., 2014; deSouza et al., 2011; Hatje et al., 2006; Hatje and Barros, 2012; Ribeiroet al., 2016). The commercial Port of Aratu, inaugurated in 1975, isespecially critical for the shipping of commodities (e.g., Cu, Fe and Mnores, fertilizers, propylene, urea, and naphtha) from the Camaçari andthe Aratu Industrial Complexes (CODEBA, 2016). In 1995, the programBahia Azul was implemented with the objective of improving the urbansewage system, to reduce inputs of solid wastes and contaminants to theBay (Borja et al., 2004). In 2011, the construction of a new oceansubmarine outfall, off the coast of Salvador, added to the efforts toimprove the quality of the waters and sediments of BTS.

2.2. Sample collection and processing

In October of 2014, scuba divers collected four cores (Fig. 1) by carefullyintroducing polycarbonate cylinders into the bottom sediments. Core CI1(9.8 m depth) was collected close to the mouth of the Paraguaçu estuary.Core CI2 (7.7 m depth) was expected to be under the influence of the Subaéestuary and TEMADRE, the harbor operated by RLAM. Core CI4 (6.6 mdepth) was collected in the vicinity of the harbor and the Industrial Complexof Aratu (CIA), whereas Core CI5 (8.9 m depth) was collected nearby therefinery RLAM. Cores (~120 cm long) were sliced at 1 cm intervals for thetop 20 cm and then at 2 cm intervals down the core. Samples were storedfrozen before being freeze-dried for further analysis. Dry bulk densities werecalculated dividing the dry weight of each slice by its volume. The chemicalanalyses were performed in the bulk fraction of the sediments.

Two surficial sediment samples (#3 and #9; Fig. 1) were also col-lected using a van Veen dredge in the Subaé estuary, which is under theinfluence of the legacy Pb from the smelter Plumbum Mineração (Hatjeet al., 2006). Fine fractions (< 63 μm) of these samples were used foranalysis of Pb isotopes. Trace metal concentrations for the Subaé es-tuary have already been presented elsewhere (Hatje et al., 2006; Hatjeand Barros, 2012; Krull et al., 2014).

For grain size analysis, sediments were first sieved through a 2 mmmesh and 0.5 mm, to separate the gravel and coarse sand fractions. Thefraction < 0.5 mm was then analyzed using a Particle Size Analyser bylaser diffraction (Cilas model 1064). Organic carbon (Corg) contentswere determined by EA-IRMS after removal of CaCO3 (Ryba andBurgess, 2002).

2.3. 210Pb analyses

Concentrations of 210Pb were determined through the analysis of itsdecay product 210Po by alpha spectrometry after addition of 209Po as an

internal tracer and microwave-assisted acid digestion (Sanchez-Cabezaet al., 1998). The concentrations of excess 210Pb (210Pbex) used to obtainthe age models were determined as the difference between total 210Pband 226Ra (supported 210Pb), which was determined for selected sam-ples along each core by low-background liquid scintillation counting(Wallac 1220 Quantulus) (Masqué et al., 2002). These concentrationswere confirmed with measurements by gamma spectrometry and foundto be in agreement with the concentrations of total 210Pb at depthsbelow the excess 210Pb horizons in each core.

2.4. Pb stable isotopes analysis

For the Pb isotopes and Cd and Ni determinations, separate samplefractions of sediments were leached with 1.75 M HNO3/3 M HCl em-ploying an ultrasonic bath for 90 min, following Graney et al. (1995).Samples then sat for 24 h before they were centrifuged and the super-natant was diluted with 0.1 N HNO3 (Optima, Fisher Chemicals, USA)and filtered through 0.45 μm PTFE syringe filter cartridges (acidcleaned). Spikes of 1 ppb In were used to correct for instrument drift.Lead concentrations were more precisely determined by isotope dilu-tion (204Pb spike). Concentrations of Pb, Cd, and Ni were determined byICP-MS (PQ2+, Fisions Instruments, UK). Recovery values for MESS-3ranged from 48 to 84% for Ni and Pb, respectively (Table S1).

The Pb isotope determination was carried out largely following theisotope ratio method of Reuer et al. (2003). The method included su-pernatant purification by column chromatography and isotope ratioanalysis on a GV/Micromass IsoProbe Multicollector MC-ICP-MS withTl addition for mass-fractionation correction, and a tailing correctionestablished by measuring the monoisotopic 209Bi spectrum at half-massintervals. The instrument was calibrated by running NBS SRM 981.Normalization to NBS SRM 981 used the absolute ratios performed byBaker et al. (2004). During the isotope ratio analysis, the data werecollected in 20 cycles. The isotope ratios were edited for outliers andaveraged with standard errors estimated from the multiple cycles. Usingthis method for 12 determinations of an in-house standard analyzedconcurrently showed reproducibility (1 s.e.) of ~0.05 permil for206Pb/207Pb and 208Pb/207Pb and ~2 permil for 206Pb/204Pb.

2.5. Trace element analysis

Homogenized and comminuted sediments were extracted em-ploying 1.0 M HCl (30% suprapur, Merk, Germany) (Hatje et al., 2006;Townsend et al., 2007). The dilute acid leach used solubilized only themore readily bioavailable fractions and left behind residual metalswithin the structure of silicate minerals (Bryan and Langston, 1992).Metals in this fraction are most readily mobilized from sediments andtherefore represent the fractions that may produce an adverse effect onbiota (Luoma and Bryan, 1981, 1982; Weimin et al., 1992). Besides, theuse of such extraction offers the best chance of detecting low to mod-erately contaminated sites by showing small differences in anthro-pogenic metal concentrations (Snape et al., 2004). Concentrations oftrace and major elements (Al, Co, Cr, Cu, Fe, Mn, Pb, V, and Zn) weredetermined by ICP OES with axially viewed configuration (Perki-nElmer, Optima 7300 DV). Sediment extractions were carried out intriplicate and relative standard deviations (RSD) were lower than 5%.Blanks and certified reference material (MESS-3, National ResearchCouncil of Canada, Canada) were utilized to assess the accuracy of theanalytical procedure. As expected, results indicated good analyticalprecision, but incomplete digestion (3–54% for Al and Pb, respectively)(Table S2).

2.6. Numerical procedures

The significance of the association between elements was assessedby Pearson correlations. A Principal component analysis (PCA) wasperformed on the data which were first log(x + 1) transformed and

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normalized to account for the different units of the variables. The re-sulting PCA loadings were then Varimax-rotated in order to achieve asimple structure.

The metal flux in the sediments was calculated as follows (Spenceret al., 2003):

=F M S[ ] ·Me i e i R i, ,

where FMe is the metal flux for the ith depth interval (μg cm−2 yr−1);[Me] is the metal concentration for the ith depth interval (μg g−1); andSR is the 210Pb-derived sediment accumulation rate at the ith depth in-terval (g cm−2 yr−1).

To compensate for mineralogy and grain size variability along se-diment cores, trace elements were normalized by Al (Loring andRantala, 1992). Enrichment Factors (EF) were then calculated by theratio of the Al normalized concentration of each element in the sedi-ment layer by the baseline value for Al normalized concentration of thesame element. Baseline values were estimated for each element usingconcentrations obtained from the bottom of sediment cores (i.e., before1900).

3. Results

3.1. Sediment characteristics

Sediments were fine-grained, mainly silt (~90%), with small dif-ferences in texture along depth (Fig. 2). Mean clay percentage rangedfrom 5% in core CI1 to 10% in core CI5. The organic carbon content incores CI2, CI4 and CI5 exhibited only a small decrease with depth(1.4 ± 0.2%, 1.2 ± 0.1%, 0.9 ± 0.2%, respectively; Fig. 2). Corg wasnearly constant in the upper 60 cm (1.8 ± 0.2) of the core CI1, fromwhere it showed a marked increase towards the bottom (3.0 ± 0.2%).The sediment cores showed an almost continuous transition from li-quefied to denser mud with depth. Dry bulk density (DBD) increasedwith depth through the cores and tended to stabilize towards the base atapproximately 0.7–0.8 g cm−3. The exception was core CI2, which DBDtended to stabilize around 0.6 g cm−3.

3.2. 210Pb geochronology

The concentration profiles of 210Pbex are shown in Fig. 2, and mainresults derived from the data are synthesized in Table 1. The horizon of210Pbex was met at 70 and 55 cm for cores CI1 and CI5, respectively,and it was not reached for cores CI2 and CI4, indicating that sedi-mentation rates are substantial at all sites. Constant concentrations of210Pbex in the upper layers were interpreted as a consequence of mixing.Mean sedimentation rates below the mixed layer, which are to be takenas upper limits, were determined using the CF:CS model (Benningeret al., 1979; Krishnaswamy et al., 1971). They were particularly highfor CI2 (2.60 ± 0.2 cm yr−1) and CI4 (1.50 ± 0.2 cm yr−1), andconsiderably lower for the two other cores (0.38–0.43 cm yr−1;Table 1).

3.3. Pb isotopes (204Pb, 206Pb, 207Pb, 208Pb)

The Pb isotopic ratios along depth (time) for each sediment core areshown in Fig. 3. Also indicated are: i) the signatures for the galena qusedfrom 1960 up to 1993 in a now-decommissioned lead smelterlocated upstream Subaé River (206Pb/207Pb = 0.96 ± 0.01,208Pb/207Pb = 2.26 ± 0.04, and 206Pb/204Pb = 14.67 ± 0.20) (DeAndrade Lima and Bernardez, 2011); ii) the preindustrial isotopicbackground (206Pb/207Pb = 1.19 ± 0.01, 208Pb/207Pb = 2.50 ± 0.11,and 206Pb/204Pb = 18.76 ± 0.02), estimated as the average ratios ofthe pre-1900 years of the cores (bottom layers); and iii) values for ga-soline used in Brazil (206Pb/207Pb = 1.16 ± 0.02,208Pb/207Pb = 2.44 ± 0.02, and 206Pb/204Pb = 18.02 ± 0.30) (Aily,2001). All isotopic profiles of each core exhibited a similar pattern.

Isotope ratios for CI1 showed only a slight decrease during the first halfof the 20th century. For 208Pb/207Pb this change was still within the es-timated background range, whereas 206Pb/204Pb and 206Pb/207Pb ratiosindicated that for the past 75 years gasoline also had a minor contribu-tion to Pb signature in this region. Core CI2 showed the greatest change,with a pronounced decrease in all isotopic ratios from around 1970 to1980 and then a slower increase. Cores CI4 and CI5 also displayedchanges in isotopic ratios, which decreased at around 1980 and 1940,respectively.

The isotopic ratios of the surficial sediment samples from the Subaéestuary were 206Pb/207Pb= 1.03 ± 0.01, 208Pb/207Pb= 2.31 ± 0.01,and 206Pb/204Pb= 15.79 ± 0.01 for #3 and 206Pb/207Pb= 1.08 ± 0.01,208Pb/207Pb= 2.36 ± 0.01, and 206Pb/204Pb= 16.68 ± 0.01 for #9.

3.4. Trace metals

Concentrations of trace elements are shown in Fig. 4. For core CI1,Cu, Zn, Pb, and V concentrations increased and reached maxima duringthe 1950s (5.8 ± 0.1 mg kg−1, 24.4 ± 0.2 mg kg−1,12.3 ± 0.2 mg kg−1, 16.7 ± 0.3 mg kg−1, respectively) and de-creased afterwards. Iron also showed an increase in concentrations fromthe bottom of the core up to 1950, and then a more substantial increasewas observed from 1950 until the 1980s. Concentration profiles of Pb,Zn, Cu, and Fe were highly correlated (0.70≤ r≤ 0.92, p < 0.05).Manganese concentrations were stable (~130 mg kg−1) throughoutthe core up until the upper layers of the core, when they increased up toabout 300 mg kg−1. Cadmium and Co also showed a tendency to in-crease towards the surface.

Concentrations of Pb, Cd, and Zn in core CI2 increased by factors of2 to 4 from the deepest sample measured (dated to the 1960s)(7.9 ± 0.2 mg kg−1, 0.01 mg kg−1, 21.3 ± 0.2 mg kg−1, respec-tively) to maxima concentrations in the mid 1980s(28.6 ± 0.1 mg kg−1, 0.44 mg kg−1, 42.8 ± 0.2 mg kg−1, respec-tively). Afterwards the concentrations of these elements decreased to-wards present. Lead and Zn concentrations were highly correlated(r = 0.97, p < 0.05). Cadmium was correlated to both Zn and Pb(r = 0.54 and 0.68, p < 0.05, respectively). Copper and V also pre-sented similar trends (r = 0.75, p < 0.05). The Cu depth profileshowed an increase between early 1970s and present time (8.2 ± 0.1up to 13.2 ± 0.2 mg kg−1). Vanadium concentrations increasedslightly from bottom (1963; 11.3 ± 0.04 mg kg−1) up until 1990s(15.5 ± 0.3 mg kg−1), when they stabilized for about ten years, thendecreases in the upper layers of the core. Vanadium was also correlatedto Zn and Pb (0.82≤ r≤ 0.88, p < 0.05). Chromium presented asmall variability, reaching a minimum value of 8.8 ± 0.1 mg kg−1 atsurface; and was significantly correlated to Al (r = 0.87, p < 0.05).Manganese distribution was correlated with Fe (r = 0.73, p < 0.05).

Trace metals, with the exception of V, presented minimum con-centrations at the base of CI4 (early 1950s). Small increases in theconcentrations of Cu, Pb, and Zn started in the late 1970s, then a no-teworthy increase occurred in concentrations of Cu, Pb, Zn, and Cdbetween early 1980s and 1990. The maximum concentration of Cu(122 ± 3.4 mg kg−1), Pb (31.9 ± 0.4 mg kg−1), and Zn(46.4 ± 1.5 mg kg−1) were up to 11, 3.5 and 1.7-fold higher thanconcentrations at the base of the core. The latter elements were highlycorrelated (0.83≤ r≤ 0.99, p < 0.05). Nickel and V concentrationsshowed a slight decrease after 1980 to a minimum concentration insurface sediments (13.5 mg kg−1 and 14.9 ± 0.4 mg kg−1, respec-tively). Manganese and Al profiles were correlated (r = 0.83,p < 0.05), and exhibited an increase in concentrations in the last15 years, with maximum values around the top of the core(664 ± 4 mg kg−1 and 6810 ± 21 mg kg−1, respectively).

Core CI5 showed increase in the Cu, Zn, Fe, and Pb concentrationprofiles (Fig. 4) since mid-20th century, reaching maximum values of13.1 ± 0.1 mg kg−1, 38.6 ± 0.8 mg kg−1, 8507 ± 117 mg kg−1,13.4 ± 0.6 mg kg−1, respectively. From the late 1970s, the

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concentrations of these elements remained relatively constant, with theexception of Pb that displayed a minor decrease towards the surface.The above-mentioned elements were highly correlated(0.95 ≤ r≤ 0.99, p < 0.05). Manganese showed a gradual increase inconcentrations, reaching the highest values at surface sediments(612 ± 3 mg kg−1). Co concentrations were constant (around6.2 ± 0.7 mg kg−1) until recent dates, when a gradual increase in

concentrations was observed, reaching the highest values at surfacesediments (12.2 ± 0.3 mg kg−1). Cobalt and Mn were highly corre-lated (r = 0.91, p < 0.05).

In general, depositional fluxes presented only minor variation forCI1 (see examples Fig. S1). Because of the high sedimentation rates, thetime span covered in CI2 was too short, therefore no clear signal of apre-industrial decrease in fluxes was observed. A slow and uniformincrease in accumulation of Pb and Zn started around 1970 and stret-ched to the late 1980s. For this period fluxes rose by 3.6 and 2.0 timesfor Pb and Zn, respectively. This trend was followed by a decrease in Pband Zn deposition until recent dates. For CI4 the metal fluxes remainedconstant until the early 1980s. Copper and Zn had an abrupt increase,reaching maximum in 2000 of up to 12 and 1.6 times the respectivefluxes in the base of the core. The maximum Pb flux was 4-fold the oneat the base of CI4 and occurred a decade earlier. Aluminium, Cr, Fe, andV in core CI5 presented minor variations in fluxes through time. Otherelements showed increase from 2 (Zn) to 4.5-fold (Pb) the fluxes on thebase of the core. It is noteworthy that the increase in fluxes started after

Fig. 2. Depth profiles of grain size classes (gray scale areas), dry bulk density (red line), organic carbon content (Corg, green line), and 210Pbex and associated standard errors (black lineand bars) for each sediment core. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Table 1Horizon of 210Pbex and sedimentation rates for cores collected in Todos os Santos Bay.

Core 210Pbex horizon (cm) SAR (g cm−2 yr−1) SR (cm yr−1)

CI1 70 0.19 ± 0.01 0.38 ± 0.02CI2 > 100 1.34 ± 0.09 2.6 ± 0.2CI4 > 100 1.00 ± 0.12 1.5 ± 0.2CI5 55 0.24 ± 0.02 0.43 ± 0.04

SAR = sediment accumulation rate; SR = sedimentation rate.

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the 1950's and that Cu, Zn, and Pb exhibited similar chronologicalprofiles. A slight decrease in fluxes could be observed in recent times forZn, Cu and Pb for CI2, CI4, and CI5.

In general, metals showed minor (1.5 < EF < 3) or moderateenrichment (3 < EF < 5) (Fig. 5). In the case of CI2, it is notable themaximum concentrations and EFs (EF = 5–6) of Pb during the 1980s,followed by an upward decreasing trend. Core CI4 presented moderateenrichment in Cu concentrations since the 1950s, which significantlyincreased during the 1990s (EF = 28). Similarly, Pb was also moder-ately enriched throughout core CI4, with the highest enrichment be-tween the mid 1980s and mid 1990s.

4. Discussion

4.1. Sedimentation rates

The results obtained in this study showed notable differences be-tween sites in terms of sedimentation rates, and the vertical distributionof physical and compositional parameters. The increase in DBD withdepth, in combination with the concentration profiles of 210Pbex, in-dicated a sedimentary environment where a relatively steady net ac-cumulation of sediments is taking place during the last century. Despitethe effects of the construction of the Pedra do Cavalo Dam in 1985,altering the fluvial water discharge and salinity field patterns in theParaguaçu estuary (Genz and Lessa, 2015), CI1 has not registered achange in sedimentation rates. Because Iguape Bay strongly buffers theeffects of the river flow, even in flood conditions (Genz et al., 2006), itmay also hinder the impacts of a possible reduction of the transport ofsuspended particulate material to the Bay. It is noteworthy that Para-guaçu is a relatively small river (annual mean discharge of 72 m3 s−1,Genz and Lessa, 2015) that, despite its large drainage area, drainsProterozoic, mostly crystalline, rocks (Souza et al., 2004) in a largesemi-arid region, and transports a relatively small amount of solids(Hatje and Barros, 2012).

The northern region of the Bay is covered by a regressive mud faciesthat is composed of a mixture of fine-grained siliciclastic rocks from the

Recôncavo Sedimentary Basin that surrounds BTS, and autochthonousbiogenic materials (Lessa et al., 2000). Fine sediments entering the Bayin suspension are likely to be trapped by the gravitational circulation,which drives a mean flow of bottom water into the bay (Cirano andLessa, 2007; Pereira and Lessa, 2009). The spatial distribution of thesedimentation rates suggested a highly skewed distribution of theseprocesses towards the CI2 area, where sediments are accumulating upto almost 7 times faster than in other areas (2.6 cm yr−1). This highsedimentation of fine sediments has caused a fast shoaling process inthe past 60 years, which, if persistent, may change the layout of thenorthwest region of BTS in a few decades, possibly allowing for theexpansion of mangroves. Frequent dredging of the navigation channelleading to TEMADRE harbor, close to CI2, can also be invoked to ac-count for the high sedimentation rates. Resuspended sediments in thechannel bed are potentially transported by gravitational circulationtowards the inner parts of the bay and over time contribute to the se-dimentation. Although smaller, Argollo (2001) and Wagener et al.(2010) also estimated the highest sedimentation rates for the Northeastpart of the BTS (0.95–0.99 cm yr−1 and 1.30 cm yr−1, respectively).The sedimentation rate for CI5 (0.43 ± 0.04 cm yr−1) was also similarto values obtained by Costa et al. (2016) and Wagener et al. (2010) forthe surrounding region (0.53 ± 0.05 cm yr−1 and 0.62 cm yr−1, re-spectively).

4.2. Chronology of environmental impacts

The man-made changes in the BTS drainage basin started aroundthe 1550s (Fig. 6) with the sugar cane monocultures that caused thedestruction of large areas of primary vegetation (de Araújo, 2000). Bythe end of the 19th century, there was a shift to tobacco farming in theParaguaçu River basin, which probably is the main reason for thechange in the Corg concentrations recorded in core CI1. The industrialdevelopment was much more recent, and it was initially driven by theproduction of the first Brazilian oil fields (1939–1950) and the con-struction of the RLAM in 1950. The RLAM promoted a significant in-crease in population (IBGE, 2016) and, from the 1960s, it also boosted

Fig. 3. Pb isotopic ratios along time as recorded in sediment cores collected at Todos os Santos Bay and in surficial sediments of the Subaé Estuary (#3 and #9). Note that the presence ofsurface mixed layers precludes the precise identification of dates in the surface layers of the cores. Galena and gasoline data are from de Andrade Lima and Bernardez (2011) and Aily(2001), respectively. The background range was estimated from the values obtained for periods before 1900.

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the industrialization, resulting in the construction of the Camaçari In-dustrial Center, the largest petrochemical complex in the southernhemisphere, as well as, the Aratu Industrial Complex (CIA), two State-owned harbors and several private ports.

4.2.1. Pb source identification and apportionmentThe major potential sources of Pb to the study areas are anthro-

pogenic, from a Pb smelter, fossil fuels and industries, and naturalsources. These sources could be distinguished using Pb isotopes.

There was a strong linear correlation between 206Pb/207Pb ratiosand 1/Pb for cores CI2-CI5 (0.919 < r < 0.953, p < 0.05;Supplementary Material Fig. S2). This indicated that there was a linearmixing of natural Pb (background) and anthropogenic Pb, from onesingle source or multiple sources with very similar Pb signature.

Core CI2 had the most distinct Pb isotope profile of the cores ana-lyzed. It was predominantly influenced by the deposition of Pb derivedfrom the Pb smelter Plumbum Mineração that operated between 1960and 1993 in Santo Amaro (Fig. 6). This smelter used galena with Pbisotopic ratios that were much less radiogenic than the values of thepreindustrial background and fossil fuel. A clear peak in the isotopicratios in CI2 (Fig. 3) coincided with the end of the period of un-controlled atmospheric emissions of the lead plant (1980) when themain exhaust chimney was extended to 90 m and a filtration systemstarted to operate (Machado et al., 2012). Dust emissions are one of themain pathways of contamination from smelters (de Andrade Lima andBernardez, 2010; Ettler, 2015; Shotyk et al., 2016). After the control ofdust atmospheric emissions, an increase in Pb isotopic ratios was ob-served, reflecting the decrease in dust discharges and the dilution of thesmelter signal recorded in sediments.

The relative contribution of the anthropogenic and natural Pbsources can be evidenced by a triple isotope diagram of the Pb isotopicratios (Fig. 7). Samples showing background values fall within the samearea, on the upper right corner of the plot, featuring high 206Pb/207Pband 206Pb/204Pb ratios. On the opposite side, the galenas (i.e., lead ore,de Andrade Lima and Bernardez (2011)) feature low 206Pb/207Pb and206Pb/204Pb ratios. Between these end members there was a clear

mixing line made out of CI2 and surficial sediment samples from Subaéestuary (#3 and #9; Fig. 7), evidencing that the surficial sedimentsfrom Subaé estuary record the greatest contribution of anthropogenicPb due to the proximity to the Pb smelter.

Most samples from cores CI1, CI4, and CI5 also fell along the mixingline, between background values, fossil fuels, and gasoline soot isotopicratios. Unlike CI2, these cores were isotopically more similar to thepreindustrial background signature than to the galena signature. Giventhe isotopic ratio profiles, the Pb measured in cores CI4 and CI5 waslikely derived from the ongoing atmospheric deposition of industrial Pband from the burning of fossil fuels from both terrestrial sources andmaritime traffic. A few samples from CI5 presented relatively lower206Pb/207Pb and 206Pb/204Pb ratios, corresponding to an increasedcontribution of Pb from fossil fuels due to the proximity of the RLAMrefinery. The CI4 features Pb isotopic ratios greater than those in CI5,but still suggesting the contribution of fossil fuels as the main source. Asleaded gasoline was phased out in the beginning of 1990s in Brazil(Gioia et al., 2006), the observed signature in the most recent sedimentsis due to Pb emissions from industrial sources. Due to the occurrence ofmixing in the surface layers, the only profile that presented a clearchange in Pb isotopic values after the phase-out of leaded gasoline(1992) was CI4.

The Pb isotopic ratios recorded in CI5 since the 1960s(206Pb/207Pb= 1.1401 ± 0.0004 and 206Pb/204Pb = 17.806 ± 0.008)are comparable to those reported (206Pb/207Pb= 1.141–1.156 and206Pb/204Pb= 17.77–18.14) by Bollhöfer and Rosman (2000) in Recife, acity with similar patterns of industrial development and population wherePb contamination is due to industrial and vehicular emissions.

The isotopic signature of CI5 in the 1940s was positioned aroundthe signal of the gasoline and the gasoline soot in the triple isotopediagram, indicating that there has been anthropogenic impact in thearea since this period. Costa et al. (2016), for the same region, observedan increase in ∑PAHs, as well as a change in total organic carbon and inthe Unresolved/Resolved ratios (UR/R) of the aliphatic componentsstarting in 1940, indicating the effects of the production of oil fields andoperations of the RLAM (Fig. 6).

Fig. 4. Concentrations of trace elements along time/depth in cores CI1, CI2, CI4, and CI5. Lead, Zn, Cu, Co, Fe, Al, V, Mn, and Cr data are from the HCl 1 M extraction, while Cd and Nidata are from the pseudo-total digestions. The black lines are plotted on the upper scale and the red lines on the lower scale of each graph. The gray area represents sediments older thanthe age dateable using the 210Pb method. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5. Profiles of enrichment factors (EFs) of each element through time in cores CI1-CI5. The gray areas represent sediments older than the age dateable using the 210Pb method.

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The inflection in the profile of the Pb isotopic ratios for CI4 wascoincident to the installation of the Aratu harbor in 1975, while for coreCI5 it was contemporaneous to the start of the production in oil fields aswell as the later operation of the RLAM. The construction of the refinerymarked a time when the transport of goods and people stopped beingexclusively maritime and was slowly substituted by road transport,

which increased the use of gasoline that at that time was mainly im-ported.

Although coal burning occurred in BTS since previous centuries(Fig. 6), the Pb isotopic ratios for coals (from Peru206Pb/207Pb = 1.193–1.122; 208Pb/206Pb = 2.029–2.103 (Díaz-Somoano et al., 2009)), and diesel (206Pb/207Pb = 1.194–1.199;206Pb/204Pb = 18.676–18.854 (Gioia et al., 2005)), alike, are veryvariable and overlap with background values. Diesel has also beenlargely used in BTS as a ship fuel. However, the variability of dieselratios and the lack of information regarding its signature for the regioncomplicate the identification of possible impacts of the usage of dieseland coal in BTS using Pb isotopes as tracers.

Among the studied cores, the 206Pb/207Pb ratio data did not varysignificantly with 1/Pb for CI1, at the mouth of the Paraguaçu River,indicating that the source of Pb accumulated at this site was basicallythe same along the time, i.e., mostly natural, and/or with only a minorcontribution of anthropogenic sources that could not be clearly iden-tified.

4.2.2. Evolution of trace metalsThe construction of the Pedra do Cavalo Dam, the São Roque do

Paraguaçu shipyard and the EIN shipyard (Fig. 1) are the major changesthat happened in the Paraguaçu River basin in the past 60 years. Evenso, elemental concentrations in CI1 do not indicate a direct relationshipwith the construction and operation of the dam, nor with the Paraguaçushipyard. However, a slight increase in Cu, Pb, Fe and Zn fluxes ob-served in the top layers suggested that the installation of the EINShipyard, which repairs and maintains oil rig platforms, may be con-tributing to the anthropogenic metal fluxes in recent times. There are afew other small business and private marinas operating in the Para-guaçu River area, many of which did not exist before the 1950s, exceptfor the traditional handmade potteries and tanneries, but it is unlikelythat they represent a major source of trace elements. The concentra-tions of Pb, Cu, Zn, Cr, and Mn throughout the core CI1 (Fig. 4) werelow, especially when compared with the concentrations of surficialsediments along the course of the Paraguaçu River (Pb:10.7–34.5 mg kg−1; Cu: 4.25–15.2 mg kg−1; Zn: 20.1–58.4 mg kg−1;Cr: 8.27–13.0 mg kg−1; Mn: 151–1594 mg kg−1; Hatje and Barros,2012). This, together with the isotopic signal of Pb, indicates that dif-fuse sources are generating relatively low impacts in the area under theinfluence of Paraguaçu mouth.

Fig. 6. Timeline of main anthropogenic sourcesof contamination to Todos os Santos Bay, Bahia.

Fig. 7. Triple isotope diagram (206Pb/204Pb versus 206Pb/207Pb) for sediment cores andsurficial samples from Subaé River (#3 and #9). Data for gasoline, ethanol, gasoline soot(Aily, 2001), diesel (Gioia et al., 2005), galena (de Andrade Lima and Bernardez, 2011),and Recife's aerosol (Bollhöfer and Rosman, 2000) are plotted for reference.

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The lead smelter, which operated in Santo Amaro until the 1990sproducing 11–32 × 106 kg of Pb year−1, was responsible for exposinglocal people to high levels of trace elements (via contaminated food,water, air and soil) (Carvalho et al., 1984, 1989, 2003; Tavares et al.,1989). The smelter also caused the contamination of the Subaé estuary,promoting a decrease in the abundance and richness of benthic mac-rofauna assemblages and impairing the ecological services promoted bythis system (Hatje et al., 2006; Hatje and Barros, 2012). The Subaéestuary is one of the most contaminated areas of BTS mainly due to thislead smelter, which still is a source of contamination through atmo-spheric dust, runoff, and groundwater dispersion of a large waste re-servoir that is poorly maintained (Hatje et al., 2006; Hatje and Barros,2012; Machado et al., 2012). Comparing the CI2 results with thecomposition of the lead smelter slag, it is noticeable that the slag's mainconstituents Fe2O3 (28%), PbO (4.1%), ZnO (9.5%) and also elementsin relatively high (Cu) and even very low (Cd) concentrations (deAndrade Lima and Bernardez, 2010) have presented increased levels inCI2 since the start of the smelter operations. Moreover, there was apronounced peak in Pb and Zn concentrations during the period of thehighest production of the smelter, followed by a decrease in con-centrations after the 1980s, when emission control measures began tobe implemented (Machado et al., 2012). The high correlation betweenZn and Pb contents, together with the Pb isotope ratios, demonstratesthat these contaminants are good markers for the impacts caused by thesmelter.

The remarkable increases in concentrations of Cu, Pb, Zn, and Cd incore CI4 since the late 1970s can be related to the development of thePort of Aratu (built in 1975) and the CIA located nearby. It is note-worthy that Cu concentrations increased by one order of magnitudeduring this period and stabilized around high values (> 100 mg kg−1)afterward. Copper concentrations were significantly correlated(r = 0.844; p < 0.05; Fig. S3) to the number of vessels docked in theAratu harbor. Concentrations followed a decrease in the number ofships after the 2008 financial crisis. Antifouling paints of boats areconsidered one of the main sources of Cu in areas of intense boat ac-tivities (Dafforn et al., 2011). After the banning of triorganotin, Cu-based pigments have been used as the main marine antifouling agent.Zinc oxide is also used as a weak biocidal pigment, but more frequentlyit has been employed in Cu-based formulations as both a booster topromote the increase in the toxicity of the latter and to facilitate theerosion process of the coating (Watermann et al., 2005). The rate ofbiocides leaching from paints and antifouling paint particles are de-pendent on the coating used, and also the hydrodynamics, pH and thepresence of additional solids as abrasives or sorbents (Turner, 2010).The leached Cu and Zn, from biocides and other chemical constituentsfrom paint matrix, are sorbed in suspended particulate material andaccumulate in bottom sediments. The profiles of these elements re-flected the intense transport of goods, including metal ores and con-centrates, through the Aratu harbor, the repair and maintenance ac-tivities that occur in boatyards, marinas, and shipyards in Aratu Bayand the burning of diesel and heavy oil in ships.

Among the industries served by the Aratu port, the SIBRA/RDM, aFe-Mn alloy production plant, located at the Aratu industrial complex,that started operations in 1970 and produces 280,000 ton of Fe-Mnalloys per year, deserves attention. It has been suggested that the Mnemitted through the chimneys and, possibly, the re-suspension of soil isnot only contributing to the contamination of the sediments, as ob-served in CI4, but also affecting the population in the vicinity of thealloy production plant (Menezes-Filho et al., 2009).

The concentration profile of Pb in CI4 presented a peak in the late1980s followed by a decrease, indicating the beginning of the phasingout of leaded gasoline. Besides gasoline, Pb potentially has several othersources in the CI4 region, such as the textile and metal industries,shipyards, and also the burning of coal to produce gas and steam.

The presence of Mn, Cu, Zn and Pb in sediments all over BTS is alsoassociated with inputs of municipal wastes. Despite the Bahia Azul

Program and the recent construction of a second ocean submarinesewage outfall in 2011 to evacuate the domestic wastewaters out of theBay, there are still large inputs of untreated sewage that compromisesthe quality of its waters and sediments. This is a serious issue in theestuaries, mangroves and coastal areas surrounded by low-incomecommunities, with very limited access to the municipal sewage system.

Vanadium is generally linked to petroleum exploration (Khalafet al., 1982; Soldi et al., 1996). Concentrations of V were 2-fold higherin the base of CI4 (1954) than in the top and it is possibly associatedwith the exploration of the Candeias oil field that started production bythe end of 1941 (time not covered by the core) and the intense flux ofvessels. The Port of Salvador was already in operation and most of thetransport was maritime at that time.

The increase in concentrations of Cu, Zn, and Pb in core CI5 sincethe mid-20th century, together with the strong correlations between Fe,Cu, Zn, and Pb, indicate that the exploration of the first Brazilian oilfields was an important source that impacted the concentrations ofthese elements in the surrounding environment. Iron, Cu, Zn, and Pb,showed a larger increase in concentrations between 1944 and 1960, aperiod that comprises of the construction (1950) and an extension ofRLAM activities (1959) together with the start of operations ofTEMADRE (1957), the private harbor of RLAM. Since the start of theRLAM construction, many jobs were created promoting the economicgrowth and subsequently attracting more investments to the area.Nowadays, RLAM produces> 30 varieties of commodities daily, in-cluding diesel, gasoline, and lubricant (Petrobrás, 2016). The stabilityin the concentrations of Pb, Cu, and Zn from 1975 onwards is possiblydue to the presence of a surface mixing layer (SML) of about 20 cm inCI5, which precludes observing any impact that the management ac-tions might have produced.

The areas of CI2 and CI4 were the most impacted by anthropogenicactivities. The relatively high metal fluxes observed in these areas arepartially due to their high sedimentation rates, up to one order ofmagnitude higher than the ones estimated for CI1 and CI5. However,the fluxes estimated here were generally within the range or even lowerthan fluxes of other regions of the world influenced by anthropogenicactivities (Table S3). Values of dry atmospheric deposition fluxes of Fe,Zn, Cu, and Mn in the Aratu harbor region were assessed by Pereiraet al. (2007). The estimated fluxes were at least one order of magnitudelower than the fluxes estimated for these elements in sediments of thereported area, indicating that currently dry deposition in this area is notthe major pathway for these elements to sediments. The wet atmo-spheric deposition might play a key role in this process; however, thereis no available data regarding this matter.

In general, for all cores, the EFs were below 4, indicating thatcontamination levels were relatively low. The exceptions were Pb (CI2and CI4) and Cu (CI4). In CI4, Cu EFs became highly enriched since1990's. This period coincides with an expansion of Brazilian partici-pation in the international market and also of the enlargement of theCamaçari Industrial Complex (Bahia, 2013), which consequently in-creased the traffic of vessels at Port of Aratu. A previous environmentalreport (CRA, 2004) also indicated that this area presented one of thehighest concentrations of Cu in suspended particulate matter (0.77 μg/L) and in the water (2.46 μg/L) of Todos os Santos Bay. Copper con-centrations in core CI4 exceeded sediment quality criteria (ThresholdEffect Level (TEL) = 35.7 mg kg−1; Buchman, 2008)) from the 1990'sto present day. The TEL is the level above which adverse effects onbiota are expected to occur occasionally.

Principal component analysis was used to assess metal provenance(Fig. 8). Two principal components (PC) were found to explain 71% ofthe total variance of the data. The PC1 (anthropogenic contribution)represented 48% of the total variance and includes Pb, Fe, Zn, Cu, Co,Mn, and V with high positive loadings, which can be considered astracers for anthropogenic activities (smelter, refinery, FeeMn alloyproduction, ports, and urban wastes). The PC1 showed a gradient ofcontamination from the bottom to top layers of each core, as well as

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from the core with the lowest trace metal concentrations (CI1) to thesites most impacted by metals (CI2 and CI4). The PC2 (natural con-tribution), which accounted for 23% of the total variability, was posi-tively correlated to Cr, Al, and clay content and negatively correlated toCorg, silt, and very fine sand. Chromium can be released to the en-vironment by weathering of crustal materials and anthropogenicsources (combustion of fossil fuels, domestic and industrial effluents),whereas Al is a typical terrigenous tracer. The high correlations of Crand Al in CI1, CI2, and CI5, and the low EFs of Cr (Fig. 5) suggest thatboth elements have natural sources, associated with clay minerals andamorphous alumino-silicates. The association of silt and Corg indicatedthat metals might be adsorbed in fine sediments by organic mattercoating. The PC2 thus represents the terrigenous contribution from thewatershed and grain size composition of sediments.

Compared to highly industrialized and urban coastal systems suchas Sepetiba (Wasserman et al., 2001) or Guanabara Bay (de CarvalhoAguiar et al., 2016), Spanish bays (Casado-Martínez et al., 2006), Tagus(Cobelo-García et al., 2011), or New South Wales estuaries (Birch et al.,2015), the metals measured here indicated a lower level of anthro-pogenic impacts. Although this study did not test the toxicity of sedi-ments, the large majority of metal concentrations, when compared toscreening tools for environmental assessment, such as TEL, did notexceed recommended values. Therefore, the risk of occurrence of ad-verse effects on biota is potentially low.

5. Conclusion

Although the colonization of the Todos os Santos Bay started in the1550s, intensification of human activities in the basin only escalated inthe mid 19th century. The exploration of oil, followed by the con-struction of industrial complexes and harbors caused increases in theconcentrations of trace elements in the sediments of the bay. Changes inthe Pb isotopic ratios also evidenced the anthropogenic fingerprint inthe area. Increases in concentrations of trace metals were associatedwith different anthropogenic activities in different areas of the bay: Pbemissions from the smelter in the Subaé estuary basin (CI2), burning offossil fuels and inputs of domestic effluents (all cores to some extent),harbor and maritime traffic (Paraguaçu/CI1 and Aratu Bay/CI4), pet-roleum related activities (Aratu Bay/CI4 and Mataripe/CI5), AratuIndustrial Complex (chemical, metallurgy, cosmetic, beverages, fertili-zers; Aratu Bay/CI4) and changes in land uses (Paraguaçu/CI1).Although all cores presented some enrichment through time, con-tamination in most of the studied areas was low to moderate. The in-tense transport of goods, the repair and maintenance activities thatoccur in boatyards, marinas, and shipyards in Aratu Bay resulted inhighly enriched Cu concentrations (EF = 28), exceeding internationalbenchmarks for which adverse effects are expected to occur.

The results of the implementation of environmental policies to im-prove the water quality of the Bay could not be evidenced for theevaluated cores. It is necessary to develop new strategies and enlargemanagement practices to stop industrial and urban wastewaterdumping into BTS so that TELs are not exceeded in the future. Theconstruction of new wastewater treatment plants and enforcement ofenvironmental regulations will reduce the discharge of contaminants,which with time will be reflected in the quality of sediments.

Acknowledgements

We gratefully acknowledge F. Barros and G. Lessa for their assis-tance collecting the cores. V. Hatje and R. Andrade thank CNPq for theresearch fellowship and scholarship, respectively. P. Masqué acknowl-edges the support of the Generalitat de Catalunya (MERS 2014 SGR-1356). This project was supported by FAPESB (FAPESB PET 34/2012)and the National Institute of Science and Technology AmbTropic (CNPq565054/2010-4).

Appendix A. Supplementary data

Supplementary data to this article can be found online at http://dx.doi.org/10.1016/j.marpolbul.2017.07.053.

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