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sea level changes over the last 7,000 years for the Brazilian coast north 28º (solid line and squares) and south of 28º (dashed line and circles), based on vermetid samples and with outliers removed (Angulo et al., 2006).
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This work aims to identify sedimentary and basal rocks structures in the Sepetiba Bay Basin (Rio de Janeiro State, SE Brazil) located in the western portion of Guanabara Graben formed during the course of Paleocene tectonic activity. Two distinct geophysical tools were used to investigate the geological records by the integration of geological surv...
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... Brazil, several works suggested that in the last 10,000 years sea level changed in most of the Brazilian east coast, showing a transgressive maximum of 4 meters above the current level at about 5,100 years BP ( Fig. 6; e.g. Martin et al., 1979a;Suguio et al., 1985;Angulo and Lessa, 1997;Angulo et al. 2006;Jesus et al., 2017;Cooper et al., 2018). Since than according to some authors should have occurred small oscillations ( Martin and Suguio, 1992). Although details of relative Holocene sea level variability along the coast of Brazil have been the ...
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... These elements were probably incorporated in the carbonate test from the bottom water and/or sedimentary pore-water or possibly even from organic matter. These metals can derive from either anthropogenic activities or from rock erosion that occurs in the region (Heilbron et al., 2004;Nascimento et al., 2019) and are present in the sediments. They are also found both in the tests of A. tepida collected in moderately to extremely polluted sediments and in the tests of those collected from the uncontaminated and pre-anthropogenic sediments of the SB, where these metals are present but in lower concentrations. ...
This work documents the presence of potentially toxic elements (PTEs) in the sediment and in tests of Ammonia tepida, one of the most common benthic foraminifera species in coastal environments worldwide. It aims to analyze if the presence of PTEs in the carbonate test of this species is related to metals concentration in the sediment aiming its application in paleoenvironmental studies. Three chambers of fifty A. tepida specimens from contaminated and uncontaminated sediments from the Sepetiba Bay, one of the most polluted coastal systems from the SE Brazil, were analyzed using an Environmental Scanning Electron Microscope coupled with an X-ray Dispersive Energy Spectrometer. The results reveal the presence of lithogenic elements and PTEs in the tests of A. tepida. Relatively high values of Pb, Hg and Sn were found in specimens recovered from both polluted and unpolluted sediment layers. The bioaccumulation index revealed higher enrichment of Cd and Cr in tests from sediments moderately to heavily polluted by Cd and to a lesser extent by Cr. The results suggest that the incorporation of metals might be controlled and affected by several factors, such as the water residence time, availability of the metals, and biogeochemical processes. As a result, applications of this method utilizing A. tepida for paleoenvironmental studies do not appear to be feasible without further research.
... Geologically, the area is formed of units of the Precambrian basement, Cretaceous alkaline rocks, and Quaternary coastal plains (Nascimento et al., 2019;Heilbron et al., 2020). Surface sediments range from sands to clay. ...
This work aims to propose new standards to assess the degree of sediment contamination in saline and brackish environments, since the legislation currently used in Brazil is based on Canadian/American regulations, which do not comply with the conditions in Brazil. This study is based on geochemical analyses of 340 surface sediment samples collected in the Green Coast region (Rio de Janeiro, Brazil), including Mangaratiba, Angra dos Reis and Ribeira coves and Ilha Grande and Sepetiba bays. This region is influenced by industrial, harbor, urban and tourist activities and was affected by a dam rupture episode that released contaminated material. The results show heterogeneity in the distribution and range of metal concentrations in the study area depending on the supply of metals from natural and anthropogenic sources. Environmental characteristics such as coastal and tidal currents, water temperature and salinity, local depth, sediment grain size, sedimentary dynamics and biogeo-chemical processes influence the dispersion or retention of metals. The pollution load index (PLI) suggests that Sepetiba Bay is the region with the most environmental degradation due to anthropogenic contamination. In this context, we propose the establishment of new levels of contamination according to the Cd, Cr, Cu, Mn, Ni, Pb, V and Zn concentrations in sediments of salt and brackish waters, considering I) background level; II) level 1-with anthropogenic influence; and III) level 2-contaminated. The results of this work also suggest that, except for zinc, the range of metal concentrations admitted by Brazilian legislation are quite permissive and not adequate for Brazilian coastal environments.
... No máximo desta transgressão, entre 5.000 e 6.000 anos, o nível do mar alcançou entre 3 a 4 metros acima do nível atual, proporcionando uma área de baía de cerca de 700 Km 2 . Neste período, as águas marinhas atingiam regiões situadas até 30 km para o interior da linha de costa atual (Amador, 1980;Nascimento et al., 2019). Vários autores têm apresentado curvas de variação do nível do oceano (Angulo & Lessa, 1997;Martin et al., 2003;Angulo et al., 2006) e descrito detalhes de registros sedimentares que permitem deduzir sobre mudanças passadas da posição da linha de costa (Alves Martins et al., 2020a). ...
A Baía de Guanabara teve seu início de formação durante o Pré-Cambriano. O sistema evoluiu durante o Cenozóico, passando recentemente por processos relacionados a alterações climáticas e atividades antrópicas. Este trabalho objetiva definir o início do Antropoceno neste sistema costeiro, a partir de registros sedimentares relacionados com a ação antrópica. A pesquisa baseia-se na análise de testemunhos e em cartografia geológica. Os resultados permitem subdividir o Antropoceno em quatro períodos de sedimentação. A camada sedimentar que marca o início deste período foi depositada em 1502, no decurso da “Pequena Idade do Gelo”, quando ocorreu o processo de ocupação dos Portugueses. Esforços de colonização, após o descobrimento, culminaram com a criação da cidade do Rio de Janeiro, em 1565. Desde então, observou-se no registro sedimentar efeitos resultantes da ocupação do território. Por exemplo, mudanças polínicas resultantes do desmatamento, da cultura da cana-de-açúcar entre os séculos XVI e XIX, e da cultura do café nos séculos XVIII e XIX, deixaram o seu registro nos sedimentos. O início do ciclo da industrialização, a partir da invenção da máquina a vapor, associado à necessidade de matérias-primas, marcou a segunda fase do Antropoceno, a partir de meados do século XVIII e início do século XX. Esta fase é identificada nos registros sedimentares com o aumento expressivo de metais. Do início do século XX até o início dos anos 50, as intervenções humanas efetuadas na orla ocidental da baía, próxima à desembocadura, alteraram o padrão hidrodinâmico, causaram a redução do hidrodinamismo e induziram a acumulação de sedimentos finos em vastas áreas da baía, marcando assim, a terceira unidade no Antropoceno. A quarta fase do Antropoceno, após meados do século XX, teve lugar num cenário de grande crescimento demográfico e industrial. A Baía de Guanabara passou a receber efluentes líquidos urbanos e industriais e grande quantidade de resíduos sólidos urbanos. O aumento acentuado no registro sedimentar de poluentes (óleo, metais pesados e substâncias tóxicas), oriundos da expansão das atividades humanas, caracterizam a quarta fase do Antropoceno.
A multiproxy approach involving grain size, geophysical (resistivity, magnetic susceptibility, and P-wave velocity), mineralogical (XRD), and geochemical (elemental, stable isotopes) data has been applied to core SP9 (128 cm long) to reconstruct natural and anthropogenic changes since ≈1850 AD (anno domine) (dating by ²¹⁰Pb and ¹²⁷Cs methods) in a distal region of Sepetiba Bay (SB), Rio de Janeiro State (SE Brazil). The analyzed core is a fine-grained sedimentary sequence (except its upper 20 cm). It comprises detrital particles derived from felsic and intermediate source rocks, as suggested by the fields defined by the biplot Zr vs TiO2 and the Al2O3/TiO2 ratios. Despite the increase in particle size at the top of the core, there was a progressive increase in the organic matter and potentially toxic elements (PTEs) contents and nutrients such as N and P. The geophysical data allowed us to identify the presence of subsurface (biogenic) gas, which suggests the occurrence of eutrophication processes in the study area despite its location in the outer region of the bay. Core SP9 records cyclical changes over the last ≈170 years in the mineralogical and elemental composition of the sediments and type of organic matter supplied to the bottom. These changes are associated with phases of more significant oceanic influence, salinity variations in the study area, and greater or lesser oxygen depletion in the sediment. These changes may have resulted from climatic oscillations or variations in the configuration and extension of the Ponta da Pombeba spit. The extent of this structure and the anthropic activities have contributed to the contamination of this area since 1975 AD. However, statistical analyses (Pearson correlations and principal components analysis) suggest that the transport and accumulation of PTEs (mainly Cd and Zn) did not strictly follow the general pattern of sedimentary dynamics prevailing in the studied area. Results indicate that this area became strongly polluted by Cd and Zn and with high ecological risk due to dredging and spoil disposal activities at sites close to the study area. It is noted that the environmental degradation reached higher levels here than in areas close to the primary source of the metals, the disabled Ingá Mercantil Company, in Madeira Island. This work demonstrates the temporal effect of dredge disposal activities in a distal region of Sepetiba Bay for the first time. It is a strong indicator that dredged spoil areas must be selected carefully, since healthy areas can become degraded due to the dumping of polluted waste.
Multiproxy approach based on textural, mineralogical, geochemical, and microfaunal analyses on a 176-cm-long core (SP8) has been applied to reconstruct the Holocene paleoenvironmental changes and disentangling natural vs. anthropogenic variability in Marambaia Cove of the Sepetiba Bay (SE Brazil). Sepetiba Bay became a lagoonal system due to the evolution and development of the Marambaia barrier island during the Holocene and the presence of an extensive river basin. Elemental concentrations from pre-anthropogenic layers from the nearby SP7 core have been used to estimate the baseline elemental concentrations for this region and to determine metals enrichment factors (EF), pollution load index (PLI), and sediment pollution index (SPI). Record of the core SP8 provides compelling evidence of the lagoon evolution differentiating the effects of potentially toxic elements (PTEs) under natural vs. anthropic forcing in the last ~ 9.5 ka BP. The study area was probably part of coastal sand ridges between ≈ 9.5 and 7.8 ka BP (radiocarbon date). Events of wash over deposited allochthonous material and organic matter between ≈ 8.6 and 7.8 ka. Climatic event 8.2 ka BP, in which the South American Summer Monsoon was intensified in Brazil causing higher rainfall and moisture was scored by an anoxic event. Accumulation of organic matter resulted in oxygen depletion and even anoxia in the sediment activating biogeochemical processes that resulted in the retention of potentially toxic elements (PTEs). After ≈ 7.8 ka BP at the onset of the Holocene sea-level rise, a marine incursion flooded the Marambaia Cove area (previously exposed to subaerial conditions). Environmental conditions became favorable for the colonization of benthic foraminifera. The Foram Stress Index (FSI) and Exp(H’bc) indicate that the environmental conditions turned from bad to more favorable since ≈ 7.8 ka BP, with maximum health reached at ≈ 5 ka BP, during the mid-Holocene relative sea-level highstand. Since then, the sedimentological and ecological proxies suggest that the system evolved to an increasing degree of confinement. Since ≈ 1975 AD, a sharp increase of silting, Cd, Zn, and organic matter also induced by anthropic activities caused major changes in foraminiferal assemblages with a significant increase of Ammonia/Elphidium Index (AEI), EF, and SPI values and decreasing of FSI and Exp(H’bc) (ecological indicators) demonstrating an evolution from “moderately polluted” to “heavily polluted” environment (bad ecological conditions), under variable suboxic conditions. Thus, core SP8 illustrates the most remarkable event of anthropogenic forcing on the geochemistry of the sediments and associated pollution loads and its negative effect on benthic organisms.
