Trace elements in an adjacent channel of an anthropized area: a case study of Baixada Santista, Southeastern Brazil

In recent decades, due to intensive industrialization, the Baixada Santista has undergone an intense process of environmental degradation. The metals are toxic and persistent in varying concentrations and oxidation states and may be incorporated in sediments and biota. Thus, understanding the importance of this contamination is necessary for coastal planning. This study provides a basis for understanding the levels of metal and As contamination in the Bertioga Channel (SP). The levels of Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sc, V and Zn in superficial sediment samples were determined by ICP-OES. The degree of sediment contamination was evaluated according to the sediment quality standards set by the Canadian environmental agency (ISQG and PEL) and by statistical tests. All values were below PEL, and most of the sample values were below ISQG, except for As, Cu and Pb. From a cluster analysis, it was possible to differentiate eastern and western parts of the channel due to their distinct hydrodynamic patterns. Furthermore, it was possible to separate the trace elements by geochemical behavior, in which Cu, Pb and Zn were linked to a small anthropogenic contribution. Thus, this study detected small anthropogenic contributions from an adjacent channel of an anthropized area, but most of the results were linked to natural geochemical processes

Control of oceanic circulation on sediment distribution in the southwestern Atlantic margin (23 to 55º S)

In this study, we interpret the role played by ocean circulation in sediment distribution on the southwestern Atlantic margin using radiogenic Nd and Pb isotopes. The latitudinal trends for Pb and Nd isotopes reflect the different current systems acting on the margin. The utilization of the sediment fingerprinting method allowed us to associate the isotopic signatures with the main oceanographic features in the area. We recognized differences between Nd and Pb sources to the Argentinean shelf (carried by the flow of Subantarctic Shelf Water) and slopes (transported by deeper flows). Sediments from Antarctica extend up to the Uruguayan margin, carried by the Upper and Lower Circumpolar Deep Water. Our data confirm that, for shelf and intermediate areas (the upper 1200 m), the transfer of sediments from the Argentinean margin to the north of 35∘ S is limited by the Subtropical Shelf Front and the basin-wide recirculated Antarctic Intermediate Water. On the southern Brazilian inner and middle shelf, it is possible to recognize the northward influence of the Río de la Plata sediments carried by the Plata Plume Water. Another flow responsible for sediment transport and deposition on the outer shelf and slope is the southward flow of the Brazil Current. Finally, we propose that the Brazil–Malvinas Confluence and the Santos Bifurcation act as boundaries of geochemical provinces in the area. A conceptual model of sediment sources and transport is provided for the southwestern Atlantic margin

Environmental Quality Index to evaluate heavy metals in sediments from Santos São Vicente Estuarine Complex (SP, Brazil)

No estudo da contaminação ambiental utilizando sedimento superficial é preciso diferenciar a componente antrópica da litogênica. A fim de minimizar a influência litogênica e facilitar a interpretação dos resultados, normalizações e a utilização de índices de qualidade ambiental são normalmente aplicados. O objetivo deste estudo foi calcular, através dos teores de metais, diferentes tipos de índices e avaliar sua aplicabilidade em regiões estuarinas degradadas, tais como a região da Baixada Santista, na qual apresenta intensa urbanização, industrialização e atividades turísticas exercendo pressão do sistema como um todo. Para isso, níveis de metais e As foram quantificados por ICP-OES e parâmetros geoquímicos como COT, porcentagem de finos, NT e δ13C e δ15N também foram obtidos. Foram aplicados oito Índices de Qualidade Ambiental e a porcentagem de finos mostrou-se essencial no cálculo destes índices, visto que é o fator que mais influencia no controle da distribuição natural de metais no sedimento. De uma maneira geral, a contaminação existente se restringe no interior do estuário, na região do Complexo Industrial de Cubatão, e sua utilização é adequada para regiões estuarinas degradadas. No estudo da contaminação em sedimentos, características como normalização pelo tamanho de grão e por um valor de referência resultando em um único valor mostraram-se essenciais. O índice Sediment Pollution Index considera todos estes, mostrando-se completo para esta finalidade.To study trace metal contamination in superficial sediment samples it is necessary to distinguish the anthropogenic and lithogenic contributions. Normalization methods and environmental quality indices are applied in order to minimize the lithogenic influence and simplify the interpretation. The aim of this study is to apply environmental quality indices, using levels of metals, and evaluate their applicability on estuarine environments as Baixada Santista in which industrial, touristic activities and urbanization exert pressure on the system as a whole. Levels of metals and As were analyzed by ICP-OES and geochemical parameters as TOC, NT, mud content, δ13C and δ15N were also obtained. A total of eight indices were applied and the mud content was essential on environmental studies, since it is the main factor on controlling the natural distribution of trace metals in sediments. In general, the prevailing contamination was confined in the inner part of the estuary around Cubatão Industrial Complex and the use of indices are suitable for estuarine system studies. On sediment contamination studies, features as normalization using a background value and the grain size, gathering all levels in one showed essential. The Sediment Pollution Index considers all, being a good index to this purpose

Mudbelts of the South and Southeast Brazil: a geochemical dataset to investigate anthropogenic impact

Mudbelts são depósitos de lama, localizados na plataforma continental, formados a partir do transporte advectivo paralelo à costa de material fino em suspensão. Devido à composição deste depósito ser majoritariamente material fino, há um potencial de acumulação de material antropogênico em virtude da maior área superficial específica dos grãos. Dessa forma, o objetivo foi verificar o potencial dos mudbelts como um registro de processos hidrodinâmicos e antropogênicos através das características geoquímicas, bem como caracterizar estes depósitos, gerando um primeiro inventário, de metais, As e 137Cs da região. Para isso, metais e As foram analisados por ICP-OES, Hg por VGA-ICP-OES e 137Cs por espectrometria gama. Atributos geoquímicos como granulometria, carbono orgânico total, nitrogênio e isótopos de carbono e nitrogênio também foram quantificados para auxiliar na discussão. Os níveis de metais indicaram ausência de contaminação, porém o fator de enriquecimento mostrou uma leve tendência de enriquecimento destes metais ao longo do tempo. O Hg apresentou valores apenas nas amostras mais costeiras, apresentando um gradiente conforme se distanciavam do continente, mostrando uma influência mais fonte pontual que atmosférica. Resultados da análise de componentes principais mostraram que existe uma componente ligada a fontes atmosféricas cujo comportamento ao longo das colunas sugere a deposição de chumbo tetraetila, utilizada como um aditivo à gasolina no Brasil, entre os anos de 1930 a 1989. Além de distinguir a porção sul da sudeste, devido a influência do Rio de la Plata, a análise de discriminantes, mostrou que as estações com fontes semelhantes se agruparam significantemente, apresentando como fonte primária o Rio de la Plata nas amostras mais ao Sul, aporte local, nas ii amostras costeiras da região de Itajaí e, a corrente do Brasil, nas amostras mais profundas da região do embaiamento de São Paulo. O radionuclídeo 137Cs foi encontrado em todas as estações, como é um nuclídeo oriundo exclusivamente de processos antropogênicos, sua presença já é um indicativo de influência antropogênica nestes depósitos. Uma avaliação estatística multivariada, junto a presença de 137Cs e Hg nas amostras permitiu concluir que os depósitos encontrados na plataforma continental são potenciais sorvedouros de elementos/materiais oriundos da ação antropogênica, e os processos que regem sua distribuição são fortemente atrelados às correntes oceanográficas junto a deposição atmosférica.Mudbelts are mud deposits, located on the continental shelves, which reflect the parallel advective transport to the coast of fine suspended material. Because their composition is mostly fine material, there is a trapping potential for anthropogenic material due to the higher specific surface area of the grains. Thus, the objective was to verify the potential of mudbelts as a record of hydrodynamic and anthropogenic processes through geochemical characteristics, as well as characterizing these deposits, generating the first inventory of metals, As and 137Cs in the region. Metals and As were analyzed by ICP-OES, Hg by VGA-ICP-OES and, 137Cs by gamma spectrometry. Geochemical attributes such as particle size, total organic carbon, nitrogen, and carbon and nitrogen isotopes were also quantified to support the discussion. The levels of metals indicated an absence of contamination, however, the enrichment factor showed a slight tendency of enrichment of these metals over time. Hg showed values only in coastal samples, presenting a gradient toward deeper areas, indicating a punctual source than atmospheric influence. Results of the principal component analysis showed that there is a component linked to atmospheric sources whose behavior along the columns suggests the deposition of tetraethyl lead, added as an additive to gasoline in Brazil, between 1930 and 1989. In addition to distinguishing the southern portion of the southeast, due to the influence of the Rio de la Plata, the discriminant analysis showed that stations with similar sources grouped significantly, with Rio de la Plata as the primary source in the southernmost samples, local input, in the coastal samples near Itajaí region and, the Brazilian current, in the deeper samples from the São Paulo Bight. The 137Cs was found in all stations, as it is a nuclide exclusively from anthropogenic processes, its presence is already an indication of ii anthropogenic influence in these deposits. A multivariate statistical evaluation, together with 137Cs and Hg in the samples allowed us to conclude that the deposits found on the continental shelf are potential sinks of elements/materials arising from anthropogenic activities, and the processes that govern their distribution are strongly linked to oceanographic currents along with the atmospheric deposition

Sedimentation in the adjacencies of a southwestern Atlantic giant carbonate ridge

Although carbonate mounds have been investigated for 100 years, few studies focus on the giant variety. The Alpha Crucis Carbonate Ridge (ACCR), a ~17 x 12-km ring-shaped ridge formed by hundreds of mounded structures, located between the 300 and 800-m isobaths and reaching a maximum height of 340 meters above the adjacent seafloor, is the first giant carbonate mounded feature described for the SW Atlantic margin. This study provides the first multiproxy approach to investigate sediments covering the ACCR and its adjacencies. Most of the area is located under the Intermediate Western Boundary Current (IWBC) flow, which carries the nutrient-rich Antarctic Intermediate Water (AAIW). Radiocarbon aging shows pronounced differences for the shallow layers (MIS3 for the top of the mounds and late Holocene for the adjacencies). Grain size data indicate the prevalence of sandy fractions on top of the mounds and muddy sediments in the adjacent areas. Fe/Ca and Ti/Ca proxies allowed for identifying mainly biogenic sedimentation in the area. However, the input of allochthonous terrigenous sediment is necessary for mound buildup, and values of Fe and Ti collected on the top of the mounds are significant. End-Members distributions and metal concentrations also allowed for recognition of distinct sources of sediment. εNd and Ln(Fe/K) indicated two primary terrigenous sources, the Precambrian rocks of the Brazilian shield (Cabo Frio end-member) and the multiple lithologies drained by the Rio de la Plata basin. Redox condition proxies indicated that the area is submitted to oxic conditions, probably reflecting the action of the IWBC. This work provides the first insight into an integrated grain-size and geochemical characterization of the Alpha Crucis Carbonate Ridge (southwestern Atlantic margin)