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

210Pb geochronology and metal concentrations in sediment cores recovered in the Alvarado Lagoon system, Veracruz, Mexico

Three sediment cores recovered from the Alvarado Lagoon System (ALS) in the Gulf of Mexico were used to reconstruct the history of metals and metalloids and their environmental importance. The sedimentary profiles were dated with ²¹⁰Pb and verified with ¹³⁷Cs. Maximum ages of 77 and 86 years were estimated. Sediment provenance was described by sedimentological and geochemical proxies. The chemical alteration index (CIA) and weathering index (CIW) revealed moderate to high intensity of weathering in the source area that is controlled tropical climatic conditions, runoff, and precipitation in the basin that feeds sediments to this coastal lagoon. The Al₂O₃/TiO₂ ratios indicated that the sediments were derived from intermediate igneous rocks. The enrichment factor values revealed the lithogenic and anthropic contribution of metals and metalloids. Cd is classified under the category extremely severe enrichment; agricultural activities, fertilizers, herbicides, and pesticides containing Cd are expected to supply this metal to the ecosystem. Factor Analysis and Principal Components provided two main factors, terrigenous and biological origins; ANOVA indicated that there are significant differences between the cores for the parameters analyzed and revealed that there are differences in depositional environments between the recovery zones of the cores. The ALS presented natural variations associated with the climatic conditions, terrigenous input, and its relationship with the hydrological variations of the main rivers. The contribution of this work was to identify the magnitude of the natural component versus the human contribution, mainly of risk metals such as Cd, to support better management of the hydrological basin that affects the ALS.

Microplastics in surface waters of tropical estuaries around a densely populated Brazilian bay

Brazil is the fourth largest producer of plastic waste in the world, but studies on pollution of rivers and estuaries by microplastics are still scarce. This study is located in the state of Bahia (Northeast region) in ten estuarine environments around Todos dos Santos Bay (TDB), the largest Brazilian bay, where more than 3 million Brazilians live. The aim of the study was the evaluation of the input of microplastics into the TSB by river. Microplastic abundance, size, morphology and water quality were determined during three sampling campaigns. All river samples were highly polluted with microplastics (mostly <150 μm), up to 33,000 items m^-3, exceeding values observed in most estuaries worldwide. The poor quality of the river water reflect the deficient treatment of domestic wastewater in the state of Bahia (49% are not treated), and in this study is shown a correlation with the abundance of microplastics, indicating their possible main source. Artisanal fishing can also contribute locally to this pollution. Morover, the results highlight the importance of sampling small microplastics (<100 μm) to avoid important underestimation of this pollution. Based on these data, the three major rivers would discharge 3.88 trillion items into the Bay each year, equivalent to 4.75 × 10⁵ m² of plastic. Further research in surface water systems is essential, given that the average wastewater treatment rates in the country and in the Northeast and North regions are only 43%, 32%, and 12%, respectively.

Fate and Trophic Transfer of Rare Earth Elements in a Tropical Estuarine Food Web

We sampled abiotic and food web components in an impacted estuarine system to assess the transfer and fate of rare earth elements (REE). REE (based on dry weight) were measured in sediments, suspended particulate matter (SPM), and organisms from different trophic levels. The highest ∑REE concentrations were measured in sediments (180 ± 4.24 mg kg^-1) and SPM (163 ± 12.6 mg kg^-1). Phytoplankton (45.7 ± 5.31 mg kg^-1), periphyton (51.6 ± 1.81 mg kg^-1), and zooplankton (68.5 ± 1.27 mg kg^-1) are the major sources of exposure and transfer of REE to the food web. REE concentrations were several orders of magnitude lower in bivalves, crustaceans, and fish (6.01 ± 0.11, 1.22 ± 0.18, and 0.059 ± 0.003 mg kg^-1, respectively) than in plankton. The ∑REE declined as a function of the trophic position, as determined by functional feeding groups and δ¹⁵N, indicating that REE were subject to trophic dilution. Our study suggests that the consumption of seafood is unlikely to be an important source of REE for humans. However, given the numerous sources of dietary introduction of REE, they should be monitored for a possible harmful cumulative effect. This study provides new key information on REE's baseline concentrations and trophic transfers and patterns.

Occurrence of mercury in polychaete species (Annelida) and their associated sediments from an important Southern Atlantic Ocean Bay

In the present study, the Hg levels in freshly collected polychaete species and their associated sediments were evaluated from Todos os Santos Bay, Northeastern Brazil. Additionally, it was also measured the Hg distribution along the annelids' body parts (anterior region, abdomen, and posterior region). Total Hg concentration was as follows: 13.6-144 μg kg^-1 (Scolelepis chilensis, deposit feeder), 8.2-122 μg kg^-1 (Laeonereis acuta, deposit feeder), 95-612 μg kg^-1 (Armandia agilis, deposit feeder); 96.6-206 μg kg^-1 (Lumbrineris sp., carnivorous), 75.3-112 μg kg^-1 (Goniada echinulate, carnivorous), and 115-198 μg kg^-1 (Branchiomma sp., suspension feeder). In turn, Hg levels in sediments ranged from 2.77 ± 0.24 to 6.38 ± 0.15 μg kg^-1. Hg concentrations found in polychaete soft tissues were higher than those found in the sediments. Specific habits, feeding behavior, trophic level, and stressful environmental conditions are the main factors affecting the Hg levels in the species studied. The bioaccumulation factor (BAF), contamination factor (CF), and ecological risk assessment (Er) were calculated. The BAF values were higher than 1 for all studied species, indicating Hg bioaccumulation in the annelids, but the low levels of CF e Er showed those Hg levels present low to no significant ecological risk for the biota and benthonic organisms living in the sediments. Finally, no statistically significant difference was observed for Hg concentration levels along the polychaete body parts.

Widespread microplastic pollution in mangrove soils of Todos os Santos Bay, northern Brazil

Microplastics have been studied in sediments from coastal and aquatic environments, but contamination of mangrove soils is still relatively unknown in most mangroves around the world. In this study, the presence of microplastics was investigated in six mangrove soils around the Todos Santos Bay (TSB), the largest and most important navigable bay on the Brazilian coast. Samples were collected at three depths (surface, 10 cm, and 30 cm) at three different distances from the lower tidal area. Ten grams of soil were sieved in a 150 μm mesh and centrifuged with ZnCl₂ solution (density of 1.5 kg dm^-3) for the extraction of microplastics. The microplastics were quantified, measured, and described using a systematic photographic method and the ImageJ program. Microplastics were abundant in all samples, with a mean of 10,782 ± 7,671 items kg^-1 (max.: 31,087 items kg^-1, only one sample <2,000 items kg^-1), higher than any other value reported worldwide. The abundances varied among the six mangroves studied, with a predominance of fibers and mean size of 196 μm. Even remote mangroves were highly polluted, reflecting a large dispersion of the pollutants. The abundance did not differ significantly between soil depths, evidencing a continuous input and burial of microplastics in the soil up to 30 cm. The investigation of the source of microplastics and their presence in water and biota is urgent in this Brazilian region, and these results emphasize the need for global actions to protect coastal ecosystems.

Polycyclic aromatic hydrocarbons in sediments and shellfish from Todos os Santos bay, Brazil

The present study evaluated the occurrence of 24 Polycyclic Aromatic Hydrocarbons (PAHs) in sediments and shellfish (Anomalocardia flexuosa, Crassostrea rhizophorae, and Mytella guyanensis) of Todos os Santos bay (BTS, Brazil). Total PAHs levels ranged from 89 to 921 ng g^-1 dry weight (d.w.) in sediments, and from 66 to 505 ng g^-1 d.w. in shellfish, signalizing that BTS was moderately contaminated by PAHs, mostly from pyrogenic activities. The bioaccumulation factor (BAF) of total PAHs ranged from 0.20 to 2.9 and did not show a clear trend among the studied species. BAFs of high molecular weight compounds were higher for A. flexuosa (specie found buried in fine sediment), while those of low molecular weight compounds were higher for C. rhizophorae (specie found in the roots of mangrove trees). High concentrations of PAHs, especially benzo[a]pyrene and dibenzo[a,h]anthracene, suggest that contamination compromises shellfish quality and raise concern about seafood consumption safety.

Human disturbance drives loss of soil organic matter and changes its stability and sources in mangroves

Mangrove soils with high organic carbon (C_org) content are likely to contain C_org that is vulnerable to remineralization during land use changes. Mangrove conversion to different land uses might deplete soil C_org stocks causing variable carbon dioxide emissions, but the extent of these emissions and the fraction of soil C_org (i.e., labile or stable/recalcitrant) that is mostly lost is poorly understood. Here, we study mangrove soil C_org degradability and its susceptibility to mineralization after mangrove disturbance. We measured changes in soil properties, organic matter (OM) stability and C_org pools and sources across a mangrove disturbance gradient (i.e., pristine forests, degraded mangroves receiving domestic sewage and shrimp farm effluents, and shrimp ponds). Results showed that the conversion of mangroves to shrimp ponds caused the most severe changes in soil properties, OM and C_org characteristics. Shrimp pond soils contained the lowest OM-C_org pools, consisted mostly of stable OM (i.e., recalcitrant and refractory; 36.0 ± 5.7% of the total OM) and enriched δ¹³C_org (-22.6 ± 2.7‰). Conversely, control mangrove soils had the largest OM-C_org pools consisting of a large unstable OM fraction (i.e., labile; 46.4 ± 4.2%) and lighter δ¹³C_org (-26.8 ± 0.4‰) being characteristic of C_org from a mangrove origin. Conversion of mangroves to shrimp ponds and its degradation by shrimp farm and domestic sewage effluents caused a loss of 97%, 61%, and 35% of soil C_org stocks in the upper meter, representing potential emissions of ~1200, 800, and 400 Mg CO₂ ha^-1, respectively. These losses were explained by enhanced OM mineralization of unstable fractions driven by the loss of the physico-chemical protection provided by fine-grained soils and vegetation cover. The differences in C_org stability among sites can be used to predict potential carbon dioxide produced during mineralization, hence aid at prioritizing areas for conservation, restoration or management.

Trace element fluxes during the "Anthropocene" in a large South American industrial and port area (Santos and São Vicente estuarine system, SE, Brazil)

The worldwide evidence of human activities on the environment led the scientific community to recognize a new geologic time unit known as the "Anthropocene." Since the twentieth century, urbanization and industrialization needs driven by population and economic growth have impacted several ecosystems including the estuaries. To assess the contamination, provenance, and fluxes of trace elements (As, Cr, Cu, Ni, Pb, Sc, V, and Zn) over the last century, a geochemical and chemometric technique was employed in sediment cores of an industrial and port region of international importance, the Santos and São Vicente Estuarine System (SSVES). The results indicated low contamination, with the highest enrichment factors (EFs) for Cu (EF = 3.1), Pb (EF = 2.7), Zn (EF = 2.4), and As (EF = 2.3) found next to the harbor area. The Pre-industrial records confirm the relatively high concentrations of As and its naturally enriched occurrence on the Brazilian shelf. Sediment accumulation rates and trace element fluxes showed a general increase over the years, since the early 1960s, associated with the "Great Acceleration" of the mid-twentieth century. These alterations are human-induced and include urbanization and industrialization. Nonetheless, as the contents and enrichment of trace elements indicate that the region is not severely polluted, we hypothesize that the contamination in the SSVES is likely related to the drainage and erosion of the urbanized adjacent area, rather than direct disposal of inorganic contaminants from the industrial activity.

Microscale extraction combined with gas chromatography/mass spectrometry for the simultaneous determination of polycyclic aromatic hydrocarbons and polycyclic aromatic sulfur heterocycles in marine sediments

This paper describes a novel method based on an ultrasound-assisted extraction microscale device (UAE-MSD) for the rapid and simultaneous determination of polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic sulfur heterocycles (PASH) in marine sediments. Solvent extraction conditions were optimized by applying a simplex-centroid mixture design. Optimum conditions were used to validate and determine the concentrations of 17 PAH and 7 PASH. The best conditions were obtained by extracting sediments with 500 µL of DCM:MeOH (65:35, v:v) over 23 min of sonication. Analytes were determined by gas chromatography/mass spectrometry in selective ion monitoring (GC-MS/SIM). Matrix effects were evaluated, and matrix-matched calibration was used for quantitation. Analytical method validation was carried out using the certified reference material NIST SRM 1941b, as well as sediment spiked with PASH at three concentration levels. Recoveries ranged between 70.0 ± 3.5% and 119 ± 9.1% for PAH and 80.6 ± 10.4% and 120 ± 10% for PASH. Linearity (R²) was ≥0.99 for all compounds. Method detection limits ranged from 8.8 to 30.2 ng g^-1, while limits of quantification ranged from 29.4 to 1011 ng g^-1. UAE-MSD was applied to marine sediments exposed to different anthropogenic impacts collected in Todos os Santos Bay, Brazil. PAH concentrations ranged from <LOQ to 667 ng g^-1, while PASH levels were <LOQ to 1152 ng g^-1. Dibenzothiophene was the compound presented in the highest concentration in all samples, with values up to 249 ng g^-1. The results indicated contributions of pyrogenic sources from all compounds. The developed method can potentially be applied to extract trace levels of compounds in different solid matrices to minimize extraction time and solvent consumption.

Distribution and fractionation of rare earth elements in sediments and mangrove soil profiles across an estuarine gradient

Many hypotheses have been raised about the controls of the distribution and fractionation of the rare earth elements (REE) in coastal ecosystems. Here, REE were measured in estuarine sediments and in six mangrove soil profiles along the estuarine salinity gradient of the Jaguaripe estuary, northeastern Brazil. The aim of this study was to evaluate the fractionation, distribution, remobilization, and possible sources of these elements. The ΣREE and Y in oxic estuarine sediments ranged from 202 to 220 mg kg^-1 and from 12 to 15 mg kg^-1, respectively. The normalized abundances to the Post Archean Australian Shale (PAAS) showed that light REE (LREE; La, Ce, Pr, and Nd) were consistently enriched over heavy REE (HREE; Er, Tm, Yb, and Lu). Among the REE, only LREE showed significant correlation with Al (r = 0.85) and Fe (r = 0.96) indicating that Al and Fe oxy-hydroxides are the main host phases of the LREE in estuarine sediments. The average ΣREE for mangrove soils throughout the salinity gradient ranged from 161 ± 18 mg kg^-1 (lower estuary) to 183 ± 16 mg kg^-1 (upper estuary). Al-normalized Mn and Fe concentrations showed small peaks down-core, indicating diagenetic remobilization. Vertical REE profiles have shown that post-deposition processes might contribute to the patterns in the abundances of the ΣREE and their fractionation at the surface and subsurface mangrove soils. Below the top 15 cm, diagenetic alteration after burial is not leading to substantial variation in the LREE/HREE profiles. The coincidence of peaks in individual REE/Al down core along with Fe and Mn peaks reflects the participation of the REE in early diagenesis. The REE abundances observed here corroborate to the characterization of the Jaguaripe estuary as a pristine system and can be used as a background for the region.

Persistent organic pollutants (POPs) and personal care products (PCPs) in the surface sediments of a large tropical bay (Todos os Santos Bay, Brazil)

The occurrence and spatial distribution of persistent organic pollutants (POPs) and personal care products (PCPs) were investigated in surface sediments of Todos os Santos Bay. Samples were Soxhlet-extracted and analyzed by gas chromatography coupled with tandem mass spectrometry. Quantification limits (QL) ranged from 0.0025 ng g^-1 for POPs to 0.25 ng g^-1 for PCPs. Of the POPs studied, only PCBs and DDTs were detectable, with concentrations ranging from <QL to 4.66 ng g^-1, with increased concentrations near urban and industrial areas. PCPs ranged from <QL to 27.5 ng g^-1 and presented a homogeneous spatial distribution, probably related to the continuous inputs of these compounds from diffuse sources. Mean contaminant inventories ranged from 0.33 ± 0.23 ng cm^-2 for DDTs to 8.3 ± 8.4 ng cm^-2 for fragrances. To the best of our knowledge, this is the first study on the occurrence of UV filters in sediments from Brazilian coastal environments.

Trace elements contamination assessment in marine sediments from different regions of the Caribbean Sea

Trace elements (TEs), rare earth elements (REEs), and methylmercury (MeHg) concentrations as well as mercury (Hg) and lead (Pb) isotope compositions in sediment samples collected from strategic locations along the Caribbean Sea were determined. The analyzed sediment samples were collected at different core depths from localities in Colombia, Cuba, Haiti, and the Dominican Republic. The evaluation of pollution assessment indices i.e. enrichment factors and geoaccumulation index revealed significant enrichment of several priority substances, such as Pb, Cd and Hg, in most of the sampling sites. Hg was found in extremely high concentrations (up to 22 ± 3 mg kg^-1) in bottom samples of Colombian core, which led the authors to further investigate this area with respect to the source for Hg contamination. The analysis of Hg isotope ratios in Colombian sediments and the Pb isotope ratios in all studied cores, helped in the identification of likely pollution sources and represents a critically important record of anthropogenic influence in the region. Finally, the REEs patterns determined in all samples, also provide a needed baseline for these contaminants in the Caribbean region.

Ecological risk of human health in sediments in a karstic river basin with high longevity population

Health and longevity are common human goals, and environmental factors can have significant impacts on human health. This study aims to investigate the historical changes and sources of trace elements in the sediments of a typical karstic river basin with high longevity population in Hechi City, Guangxi, China and to evaluate the ecological risks of trace elements in sediments. The results showed that over the past 100 years, the contents of trace elements in the sediments were lower in the upper reaches than in the middle and lower reaches of the river. The sediments had high trace element contents in 1950-1959 and 1989-1998, while low contents appeared after 1998. These periods correspond to China's industrial growth in the early 1950s, the Great Leap Forward movement in the late 1950s, the reform and opening-up policy implemented in the 1980s-1990s and the environmental protection policies to strengthen pollution control that have been implemented since 2000. Limestone soil and carbonate rock are the main sources of sediment in the basin. Although the geological background values of Cd and other trace elements in the basin were relatively high, the high calcium content and alkalinity of the water and sediment in the basin reduced the bioavailability of Cd and other heavy metals. The mainstream of Panyang River had a low environmental risk, but the tributary Bama River where there is dense population poses a moderate risk.

Evaluating Spatiotemporal Resolution of Trace Element Concentrations and Pb Isotopic Compositions of Honeybees and Hive Products as Biomonitors for Urban Metal Distribution

Assessing metal distributions in cities is an important aspect of urban environmental quality management. Western honeybees (Apis mellifera) and their products are biomonitors that can elucidate small-scale metal distribution within a city. We compare range and variations in trace element (TE) concentrations and lead (Pb) isotopic compositions of honey, bee tissue, bee pollen, and propolis collected throughout Metro Vancouver (BC, Canada). Honey, bee, and bee pollen results have similar TE and isotopic trends; samples collected in urban and industrialized areas exhibit elevated concentrations of anthropogenically influenced TE (e.g., Pb, Zn, V, and Ti) and a less radiogenic Pb isotopic composition (i.e., lower 206Pb/207Pb and elevated 208Pb/206Pb) relative to their suburban and rural counterparts. For example, 206Pb/207Pb, 208Pb/206Pb in honey range from 1.126, 2.131 and 1.184, 2.063; extremes measured in honey from urban and suburban/rural areas, respectively. Except for propolis, measured and interpolated (kriged) results in all materials reflect the immediate zoning or land use setting near the hive, providing kilometer-scale geospatial resolution, suitable for monitoring urban systems. Statistical analysis reveals that no systematic variations or intra- or inter-annual trends exist in TE concentrations or Pb isotopic compositions, including among sampling and field methods (i.e., old vs. new hive equipment and honey from the brood nest box vs. honey super). The results of this systematic study using honeybees and hive products in Metro Vancouver provide a robust, current baseline for future comparison of local land use and environmental policy change.

Combining geochemical and chemometric tools to assess the environmental impact of potentially toxic elements in surface sediment samples from an urban river

This article investigates sediments collected from the banks of the Subaé River located in Todos os Santos Bay in the state of Bahia, Brazil, in 2018, twenty-five years after the closing of a former lead alloy processing plant. Ten sediment samples were collected at different points of the course of the river and its estuarine region. Chemometric tools were used to determine geochemical correlations between the organic matter content and concentration of sulfides and potentially toxic metals. The inorganic geochemical variables (enrichment factor [EF]) used in this evaluation were concentrations of the Pb, Cd, Cu, Zn, and Ni. Chemical element analyses were performed using ICP-OES. To assess the interaction between metals and sulfide or metals and organic matter, concentrations of Pb, Cd, Cu, Zn, Ni, sulfide, and the silt-clay fraction constituted the organic geochemical parameters selected to characterize the amount of organic matter present in Subaé River sediment samples, determining the carbon content (%TOC) to compose the matrix of the principal component analysis (PCA) and hierarchical cluster analysis. PCA showed that 88.3% of the samples were representative for assessing correlations between geochemical variables. A tendency toward binding was found among Cu, Cd, Ni, and sulfide, as well as the silt-clay fraction. The concentrations (mg kg^-1) of lead, zinc, and copper were higher in both collection campaigns, ranging from 4.72 to 31.34, 12.76 to 54.24, and 5.34 to 31.37, respectively. Pb and Zn were presented in elemental form when assessed as a function of the pH and Eh of the environment. Except for Cd (EF: 0.51 to 5.49), the other elements exhibited little or no potential pollution in the aquatic environment of the Subaé River.

PCBs occurrence in marine bivalves and fish from Todos os Santos Bay, Bahia, Brazil

In order to evaluate contamination by polychlorinated biphenyls (PCBs) in a tropical bay exposed to different anthropogenic pressures, samples of bivalves: mangrove oyster (Crassotrea rhizophorae), mangrove mussel (Mytella guyanensis)and clams (Anomalocardia brasiliana), were collected in different parts of Todos os Santos Bay, Bahia, Brazil. In addition, samples of bivalves and fish, purchased from a seafood market in the city of Salvador were analyzed to evaluate human exposure to PCBs through ingestion. Identification and quantification of PCBs were done by GC/MS after microwave extraction and purification with sulfuric acid. In bivalves, concentrations ranged from <0.08 to 50.1 ng g ^-1 (dry weight), with the highest values being detected in mangrove oyster, followed by clams and mangrove mussel of the Subaé estuary and Madre de Deus/Mataripe; regions known to be impacted by anthropic activities. From the total of the 12 fish species analyzed, only 5 presented levels of PCBs above the detection limit, ranging from 0.23 to 4.55 ng g ^-1 and 0.51 to 26.05 ng g ^-1 by dry weight and lipid weight, respectively. In general, concentrations of PCBs on the bay are lower than in most regions around the world, especially those located in the Northern Hemisphere. Indexes indicated that local biota and seafood from the fish market are not adversely impacted by PCBs and do not represent a risk to human health.

Historical records of mercury deposition in dated sediment cores reveal the impacts of the legacy and present-day human activities in Todos os Santos Bay, Northeast Brazil

We determined depth profiles of total mercury (T-Hg) in six ²¹⁰Pb-dated sediment cores from Todos os Santos Bay to reconstruct the history of anthropogenic Hg accumulation. We also assessed superficial sediments samples from five estuaries. T-Hg concentrations (5-3500 μg kg^-1) presented a large spatial and temporal variability. T-Hg concentrations in Ribeira Bay increased up to 200-fold along time, whereas the fluxes of T-Hg are substantially higher (up to 10,000 fold) than present-day wet deposition for industrialized areas. Sedimentary records indicate that a chlor-alkali plant has been the main source of Hg pollution until the present, although the T-Hg records suggest that harbor, shrimp farming, and oil refinery activities, besides Hg atmospheric depositions, are important across the bay. Sediments in the Ribeira Bay act as an important Hg sink. If sediments are eroded or disturbed, they may release Hg, thus posing a serious risk to wildlife and ecosystem health. CAPSULE: Sedimentary cores provide data on preindustrial levels and also anthropogenic fluxes of Hg for the appraisal of the magnitude, processes and potential risks of the contamination.

Temporal metal concentration in coastal sediment at the north region of Persian Gulf

The purpose of this article is to study, result of metal concentration in two-sediment cores from Persian Gulf. Age of sediment is determined by C¹⁴ isotope method and bulk concentration is determined by ICP. This research output shows that, age of BandareAbbas core back to 9660 and Bushehr core to 15,600 years ago. Also,concentration in BandareAbbas and Bushehr cores respectively change as, As (1.08-11.76 Vs 5.2-13.09), Ba (15.03-129.5 Vs 73.9-120.4), Cd (0.09-0.46 Vs 0.09-0.18), Li (5.66-58.5 Vs 15.3-33.4), Mo (0.3-0.75 Vs 0.3-0.8), Mg (7928.4-15,503.9 Vs 13,102.8-17,227.8), Mn (110.6-566.4 Vs 279.3-429.1), Na (8905.47-27,993.3 Vs 9357.7-27,541.4), Ni (13.3-110.3 Vs 37.1-88.4), Pb (0.5-42.5 Vs 2.5-13.6), Sr (407.5-1773.2 Vs 440.3-1596.9), Zn (13.05-71.2Vs22.4-50.5), Fe (0.46-4.07 Vs 1.7-3.18), Ca (9.25-23.3 Vs 13.8-19.2) and Al (0.62-8.15 Vs 2.48-4.65). Moreover different pollution index investigation represent that except Ca, the rest of the metal elements do not show pollution.

A tropical bay as a reference area defined by multiple lines of evidences

References areas are sites that have undergone little or no anthropogenic impact and therefore represent the natural state of an environment. The objective of this study was to test if the Camamu Bay (CB), Bahia, can be used as a reference area for tropical coastal environments. Trace and major elements, polycyclic aromatic hydrocarbons (PAH), and the structure of the benthic macrofauna were determined. To compare the studied sites and identify the possible occurrence of anomalous concentrations, trace elements were normalized by Al and linear regressions were also performed. For all trace elements (except Cu), regressions showed a significant correlation (p<0.05) and few outliers (<3% of cases), showing that the concentrations found represent natural values for this bay. In the case of Cu, the highest concentrations were found near small municipalities, which may be associated with domestic sewage. About 60% of the organic compounds occurred at levels below the limit of quantification (<0.26ngg^-1). The sum of PAHs was low for all stations, ranging from 1.17 to 313ngg^-1. The benthic assemblages also indicated that the CB is a healthy, well-preserved ecosystem that deserves conservation efforts. The integrated use of geochemical and biotic data supported the use of CB as a reference area. Capsule: Organic and inorganic contaminants together with macrobenthic assemblages indicated that Camamu Bay is a pristine, tropical reference area.