A granulometria do depósito sedimentar pode ser um indicador da energia que atua no processo dinâmico de deposição e de transporte sedimentar. Tanto a deposição quanto o transporte resultam em um selecionamento das partículas, o qual é influenciado tanto pela velocidade de decantação das partículas quanto pelo transporte como carga de fundo. Isso porque geralmente em áreas com maior energia, as partículas mais finas tendem a ser mantidas em suspensão por mais tempo, resultando em um depósito com granulometria tendenciando para frações mais grossas (arenosas por exemplo). Teoricamente, por outro lado, em áreas de menor energia, a decantação de partículas mais finas ocorre em maior escala, resultando em um pacote sedimentar que apresenta padrão granulométrico fino, com maior proporção de silte e argila. Dessa forma, a arquitetura do depósito pode representar os processos dinâmicos sofridos pelas partículas ali encontradas. Neste estudo, buscou-se identificar os modos de transporte dominantes que atuam sobre os sedimentos lamosos da lama terrígena em ambiente de mar profundo da margem continental capixaba, utilizando uma análise de decomposição das curvas granulométricas (BasEMMA; Zhang et al., 2020).

The Fundão dam failure, the worst environmental disaster in Brazilian history, launched 50 million m ³ of iron ore tailings mud through the Doce River, reaching the Atlantic Ocean. Generally, mine tailings increase the sediment inflow, leading to mud burial of epibenthic macrofauna, and the raise of metal(oid)s concentration causing macrofauna long-term changes. After almost four years, tailings mud was still spreading on the Doce River Shelf, while impacts on marine macrofauna were still unknown. Herein, the IMS index (a tracer of Fundão dam tailings mud), sediment variables, organic pollutants, and metal(oid)s were integrated to uncover the drives of macrofauna structure from Costas da Algas to Abrolhos bank MPAs. Tailings mud was present only in Doce River Mouth and Degredo, organic pollutants and metal(oid)s above safety levels were concentrated in those same areas. Tailings mud (IMS index) drastically reduced species richness and diversity, favoring the abundance of opportunistic species. Mud, IMS index and Al, Ba, and V, metal(oid)s linked to dam failure, structured macrofauna composition in this impacted area, dominated by resistant groups as Nuculidae, Spionidae, and Magelonidae. Conversely, an opposite pattern was found for further and deeper sites with high CaCO3 content and total nitrogen that also showed large grain size, in areas known to harbour biogenic structures, sustaining a macrofauna composition distinct from the impacted areas, dominated by Syllidae and Crassatellidae, sensitives to impacts. Macrofauna composition was most structured by sediment variables, followed by the intersection between metal(oid)s-IMS and Mud, both gradients acting almost entirely on a broad spatial scale. Benthic macrofauna at the Doce River Shelf is still impacted by Fundão dam tailings mud, even after almost four years of the disaster, and may continue to, since the influx of tailings does not stop, and sediment resuspension is a recurrent source for those impacts.

After the Fundão iron ore mining dam rupture in November 2015, yellow/ocher emulsions never before reported on the continental shelf adjacent to the Doce River began to be seen, both in coalesced and foam forms. XRD analyses pointed to a prevailing composition of iron and kaolinite with a substantial contribution of an organic-metallic compound, measured in multiple periods over 2 years of sampling. Optical microscopy images allowed the identification of micelles composed of nanoparticles of iron oxyhydroxide making up this emulsion. The generation of dendritic snowflake-shaped microcrystals on fiber filters after water sample filtration and heating confirmed the presence of micelles composed of iron oxyhydroxide nanoparticles enveloped by organic polymers. After losing water, the micelles may act as a self-assembly template seed, where the polymer acts in the oriented adsorption of nanoparticles according to their crystallographic structure. The study brought to light the distinct behavior of a portion of the tailings material, which has already been reported to not have the same flocculation process as the clay minerals previously found in the suspended particulate material (SPM) before the dam rupture.

Since November of 2015, when ore tailings from a dam rupture reached the Atlantic Ocean, researchers are trying to assess the degree of impact across the Doce River and adjacent coastal area. This study aims to use the zooplankton dynamics as a tool to evaluate the environmental impact in the coastal region, five years after the rupture, during periods of low and high river flow. Doce River flow varied from 49 to 5179 m ³/s and structured the zooplankton community between periods of low and high river flow, but salinity and chlorophyll-a had stronger correlation with depth (r = 0.40 and − 0.40 respectively) than with the Doce River discharge variation along the sampling period (r < 0.2). On the other hand, inorganic particles in the water and total metal concentration (dissolved + particulate), used as tracers of the iron enriched tailing (Al, Cd, Cr, Cu, Fe, V), were correlated with fluvial discharge and showed to be the main factor driving the zooplankton community dynamics. For assessing the degree of environmental impact, we tested the ecological indexes for the zooplankton community. Margalef Richness, Pielou Evenness and Shannon-Wiener Diversity varied from 2.52, 0.40 and 1.39 (all registered during high river flow period) to 9.02, 0.85 and 3.44 (all registered during low river flow period), respectively. Along with those community indicators, we evaluated the response of representative taxonomical genera such as Paracalanus, Oikopleura and Temora, regarding the Doce River flow, and found population patterns that established a baseline for future monitoring in the region. Our results showed that the zooplankton community is more fragile when the river discharge is stronger, and this pattern is confirmed by all indicators tested.

In the past several decades, anthropogenic changes throughout drainage basins have threatened physical, hydrological and ecological river-to-ocean continuum balances. Dams are one of these anthropogenic influences that can seriously affect sediment fluxes to the ocean. Here, we investigate the formation and dispersion of a high-concentration mud suspension (HCMS) at a river mouth due to a tailing dam failure. In November 2015, the Fundão dam (Mariana-MG, Southeast Brazil) failure released approximately 39.2 million m ³ of tailings into the Doce River system. The slurry travelled 660 km down to the river mouth, reaching the Atlantic Ocean. Pre- and Post-dam failure surveys were used to investigate temporal and spatial changes in Suspended Particulate Matter (SPM) concentration, seabed sediment grain size and seabed sediment bulk density along the inner shelf. Results indicate that the combination of the tailing dam failure with an extremely dry seasonal condition led to the formation of a HCMS, altering, at least in a short term, the sedimentary processes along the inner shelf, leading to high sedimentation rates and low seabed sediment bulk density. Changes in particle size defined by an increase in clay content, a significant increase in SPM concentration in the inner shelf and a decrease in seabed sediment bulk density were observed as a result of the dam failure. SPM concentrations were higher near the seabed than at the surface, reaching up to 9000 mg/l. The highest SPM concentration measured during a major flood in January 2014 reached around 100 mg/l, The combination of a HCMS with tailings high clay content resulted in low values of seabed sediment bulk density and the formation of fluid mud along the inner shelf. In the first week after the tailings arrival, a 5 cm thick tailing fluid mud was observed. In this stage of bed formation, bed strength is lower, easing particle reentrainment by waves or currents. Thus, tailings could be advected, spreading the impact along the coast.

This work aims to characterize, in mineral and chemical terms, the ore tailings related to the Mariana disaster (MG, Brazil), occurred on 5 November 2015, and assess its correlation with sediments found in the continental shelf adjacent to the Doce River mouth (ES, Brazil). This study uses samples of tailings and seabed sediments collected at the mouth of the Doce River from 2012 to 2019. Elemental compositions of all samples were determined by X-ray fluorescence measurements; however, Synchrotron Resonant X-Ray Diffraction proved to be a remarkable technique to characterize the crystallographic phases of iron present in sediments. Studies and analyzes of the sediment samples showed that the tailings have a notable feature of the iron-crystallographic phases, mainly observed in the period after the Fundão dam failure, as compared with sediments collected in the period before. This set of iron-containing mineral phases, here called the Iron Mineralogical Set (IMS), consists of the main phases of hematite and magnetite and the minority phases of goethite and greenalite and it is used as a marker of tailings. Mass ac magnetic susceptibility measures supported the concept of the IMS as a marker. It is suggested a relationship between the content of the IMS in the sediment samples as a function of the measures of mass magnetic susceptibility. The IMS had shown the influence of tailings on the sea bed sediment indicating that there is no possibility, at the current stage, of predicting how many years this material will still be at the seabed.

Zooplankton were sampled five days after the tailings from the Samarco dam rupture reached the ocean in the coastal region at the mouth of the Doce River. This was one of the largest environmental disasters in Brazilian history, and the impacts on the marine biota are not yet fully understood. This study aimed to evaluate the zooplankton community short term responses to the metal enrichment after the tailings reached the coastal region in different scenarios. Our results showed an acute impact on the zooplankton community, which peaked in abundance (222,958.60 ind/m ³) and decreased in diversity (H′ = 1.23) near the river mouth. Two copepod species, Parvocalanus sp. and Oithona nana, composed up to 61% of the total abundance and they were correlated with concentrations of Fe, Pb, Cu and Zn in particulate fraction. These species feed opportunistically on nanophytoplankton, which dominated the autotroph community, possibly in response to the iron enrichment caused by the mud flow. A shift on zooplankton species composition was also observed. During the first three days, we found the presence of oceanic species in the 20 and 30 m isobaths during an incomplete upwelling event, which directly correlated with the presence of Calanoides carinatus. However, only three days later, following a cold front passage and consequent increase of water turbidity, those species were already absent, and the zooplankton community was significantly altered (PERMANOVA, df = 1, pseudo-F = 9.2247, p = .001). Zooplankton responded quickly to the environmental changes detected during our sampling period and proved to be key factors in costal monitoring, especially in dynamic oceanographic areas such as the Doce River coastal region.

Paq proxy was applied on mid and long-chain n-alkanes in order to develop an index to assist in the long-term assessment of changes and exchanges between aquatic communities in estuarine environments as a result of increased saline incursion. New boundaries are proposed according to n-alkanes abundance in the leaves of local mangrove tree species for better definition of emergent aquatic plant end-member. Molecular distribution and δ13C isotopic signatures of n-alkanes were also used to support the parameter. A predominance of odd carbon-numbered long chain (> C27 n-alkanes) indicated a main terrestrial input, although mid-chain n-alkanes (23 and 25 carbons) were also identified. Short-chain n-alkanes (< 19) were absent or found in a very small concentration. Carbon Preference Index and C/N ratio reinforced a terrestrial origin for the sedimentary organic matter. δ13C signatures of n-alkanes for C23, C25, C29 and C31 were characteristic of mangrove input, ranging from -27.57 ‰ (C23) to -34.40 ‰ (C29) for Piraquê-Mirim River (PM) and from -27.36 ‰ (C23) to -32.84 ‰ (C31) for Piraquê-Açu River (PA) without any particular trend. Paq proxy was successfully used to identify rises in marine macrophytes (mid-chain n-alkanes) input mainly in the confluence and PM probably as consequence of drought periods. The confluence presented a mixing sources of OM. PA was identified as a stable mangrove environment while PM was characterized by pulses of marine macrophytes input and should be managed with care in respect to its catchment for water use and dam constructions as a shortage of fresh water can alter the estuarine ecology.

In November 2015, a tailing dam failure dumped approximately 32 million m3 of very fine iron-rich tailing material into the Doce River watershed, Southeast Brazil. A highly concentrated tailing slurry travelled 660 km down to the river mouth, reaching the Atlantic Ocean. The changes in flocculation patterns of cohesive sediments after dam failure and the deposition of tailing material are investigated. A series of experiments were performed using sediments collected from inside the iron ore mining dam, from a side bank inside the Doce River (after failure), and from the inner continental shelf before and after the tailing deposition. The experiments were performed in settling columns with an optical backscatter sensor and a high resolution digital camera, using only the samples mud fraction (<63 μm). Comparing settling curves, settling velocities and floc sizes showed that the flocculation and settling behavior of cohesive sediments has changed to a new sort of particles of a more homogeneous size and delayed settlement. Sediment from inside the mining dam was almost entirely composed of heavy minerals with fast settling velocity and very small size, but a fraction of it was very similar to the sediment from the side bank of the river: small size with very slow settling velocities and delayed deposition. Sediments from the continental shelf after the tailing deposition differed from sediments before the failure in the presence of heavy minerals, delayed settlement and a narrower range of floc size. We conclude that the tailing deposition increased the residence time and dispersion of mud fraction sediments in the marine water column due to deposition of a finer, porous and/or metallic coating material.

In November 2015, a mining dam failure dumped approximately 32 million m3 of very fine iron-rich tailing material into the Doce River watershed and the adjacent continental shelf, Southeast Brazil. Previous settling column experiments demonstrated different properties and behavior of flocs between natural sediment samples and those contaminated by the iron ore tailing, in which the presence of smaller and more porous flocs in the last was explained by a very fine fraction of clay and or a metallic coating (Grilo et al., 2018). As nanoparticles possess unique physical and chemical properties due to their high specific area and nanoscale size, their transport, persistence and bioavailability in the environment are essential aspects to be considered in risk assessment and management (Wiesner et al., 2009). Nanoparticles such as iron oxyhydroxide hold high reactivity with different ions (Antelo et al., 2005), where adsorption may increase or decrease the charge on the surface of nanoparticles and affect their stability (Breeuwsma and Lyklema, 1973).

The Piraquê-Açú and Piraquê-Mirim estuarine system (PAPMES) is considered to be a hydrologically unaltered estuary; however, several human activities including introduction of pollutants may have contributed to changes in this system. We have studied hydrocarbons, major elements (Al, Mg, Fe and Mn), trace elements (As, Ba, Cd, Co, Cr, Cu, Li, Ni, Pb, V and Zn), Corg./Ntotal ratio, and δ13C and δ15N stable isotopic composition of organic matter to assess the natural and anthropogenic depositional record in three sediment cores dated by 210Pb geochronology. The sediments showed a strong terrestrial C3 plant contribution to organic matter input in the rivers (−29.2 ≤ δ13C ≤ −25.1h; 2.1 ≤ δ15N ≤ 5.3h; 23.3 ≤ Corg./Ntotal ≤ 53.9), with a higher phytoplankton influence downstream (−29.3 ≤ δ13C ≤ −20.7h; 0.4 ≤ δ15N ≤ 6.6h, and 15.4 ≤ Corg./Ntotal ≤ 34.4). Greater n-alkane concentrations typical of higher plants (nC27, nC29, nC31) confirmed the terrestrial inputs. There was no indication of contamination by petrogenic sources, but relatively high amounts of 17β(H), 21β(H) and 17β(H), 21α(H) terpanes, indicate a possible association with biogenic activities (bacteria). The distributions of major and trace elements were associated with a high lithogenic input and iron and manganese oxides/hydroxides. Although there is little evidence of enrichment by direct human activity, the downstream sediments may be influenced by deforestation for charcoal production which occurred between the 1950s and 70s, exposing soils to weathering and erosion.

A bacia de drenagem do Rio Doce é uma das mais importantes do Brasil, fornecendo grande aporte de sedimento para a plataforma continental adjacente ao estado do Espírito Santo. Em novembro de 2015 o episódio do rompimento da barragem de rejeitos de minério na cidade de Mariana mudou a realidade desta relevante rede hidrográfica, pois cerca de 55 milhões de metros cúbicos de lama de rejeito foram despejados no Rio Doce, chegando posteriormente ao mar. Tendo em vista que este foi o pior desastre ambiental da história do país, torna-se de fundamental importância monitorar a região atingida. Sendo assim, diversas campanhas amostrais foram realizadas com intuito de verificar o impacto causado pelo desastre na região da plataforma continental adjacente ao Rio Doce. Neste trabalho foram abordadas as análises conduzidas no sedimento superficial, que incluem a granulometria e a densidade. A malha amostral inicial foi delimitada de forma a cobrir uma radial à foz do rio, sendo esta alterada (pontos amostrais adicionados) de acordo com o deslocamento da pluma de MPS. Para a análise comparativa dos dados foram utilizados como background estudos anteriores à chegada da lama de rejeitos. A granulometria foi realizada via peneiramento a úmido, que separou a fração de lama do conteúdo de areia. A lama foi analisada em granulômetro a laser (Malvern) para determinar o conteúdo de silte e argila. Junto a estes dados foram agregadas as análises de densidade, que permitiram verificar a sedimentação recente através da avaliação da compactação do sedimento e a presença de uma camada de fundo móvel, que indicam o impacto causado pelo rejeito de minério na região da plataforma. Com a análise dos dados de granulometria e densidade do sedimento superficial foi possível verificar um comportamento atípico, com a presença de concentrações elevadas da fração de argila, incluindo a presença de material coloidal. O desastre ocorreu em um momento de extrema seca na bacia do Rio Doce, ocasionando o aporte anormal de um volume extremamente alto de sedimento na plataforma, sendo inclusive, muito maior do que o aporte verificado para os eventos de fortes chuvas na bacia do rio no final do ano de 2013 e início de 2014. Uma vez na plataforma, o comportamento da lama de rejeito junto ao fundo variou principalmente em função da vazão e das correntes de fundo direcionadas pelo vento. A deposição preferencial do material ocorreu na região da plataforma interna junto à foz em direção ao sul da desembocadura. A ocorrência de deposição de argila em locais onde esta fração era incomum anteriormente indicou uma alteração significativa no padrão de deposição do sedimento. Também foi possível identificar que a deposição se manteve restrita até a isóbata de 30 m de profundidade.

Although, estuarine ecosystems have an ecological and economical importance as they have a high biological productivity and occur within a unique and dynamic environment, they have been subjected to anthropogenic alterations. The Great Vitória Estuarine System (GVES), Espírito Santo State, Brazil, is not an exception, as urbanization is growing around it with a high quantity of sewage been added to the system. In order to evaluate the eutrophication state as well as the meiofauna response to it, several parameters in both sediments and in the water column were assessed. Orthophosphate, nitrite, nitrate, ammonia, chla and Fecal Coliform counts (FC) ranged from 0.2 to 3.2 μM, 0.25 to 1.14 μM, 1.83 to 0.19μM, 4.19 to 49.23 μM, 0.61 to 6.72 μg/L and 14 to 5.0x104 MPN/100 mL of water, respectively. These results showed that the GVES is under an eutrophication process and that the Passagem Channel experienced the largest impacts. Sewage plays an important role in this eutrophication process as indicated by PCA and correlations tests. The density of meiofauna showed similar values to those found in environments with similar levels of anthropogenic stress. This multi-approach evaluation revealed several aspects of the impacted estuary and could be used as an important tool to manage better the estuary.

Although the Passagem Channel estuary, Espírito Santo State, Brazil, is located in an urbanized and industrialized region, it has a large mangrove system. Here we examined natural and anthropogenic inputs that may influence trace metal (Cd, Cr, Cu, Ni, Sc, Pb and Zn) and hydrocarbon (n-alkane and terpane) deposition in three sediment cores collected in the tidal flat zone of the estuary. The cores were also analyzed for carbonate, grain size and stable isotopic composition (δ13Corg. and δ15Ntotal). Metal enrichment and its association to petroleum hydrocarbons in the surficial sediments of one of the cores, indicate crude oil and derivative inputs, possibly from small vessels and road run-off from local heavy automobile traffic. At the landward sites, the major contributions for metals and hydrocarbons are from natural sources, but in one case, Cu may have been enriched by domestic effluent inputs.

Estuaries are coastal environments that normally accumulate many contaminants in their sediments, where the estuary of the Canal da Passagem (Vitória-ES) falls in this type of coastal environment, because it is a region that has been suffering with urbanization and industrialization around. In order to evaluate the quality of the sediment of the estuary, were analyzed trace metals cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), Scandium (Sc) and Zinc (Zn), hydrocarbons (n-alkanes and hopanes), organic carbon and total nitrogen ratio (Corg/Ntotal) and stable isotopes (δ13C) in 3 sediment cores (P1, P2 and P3). The metal concentrations ranged from 0.06 to 0.93 μg/g (Cd) 4.03 to 63.45 μg/g (Cr) 1.27 to 32.72 μg/g (Cu), 1.12 - 10, 05 μg / g (Ni), 1.69 to 22.85 μg/g (Pb), 0.62 to 4.29 μg/g (Sc) and 19.62 to 166.17 μg/g (Zn).The concentrations hydrocarbon were 0.29 to 32.50 μg/g for the n-alkanes and from 0.06 to 14.44 μg/g for the hopanes. While the values of Corg/Ntotal and δ13C varied from 12.96 to 60.96, -36.20 to -25.01‰, respectively. The results show that the estuary of the Canal da Passagem has suffered an accumulation of pollutants over time, especially in the region of core P1, which showed characteristics of anthropogenic contribution to the contamination with oil and derivatives being the main source of metals and hopanes.

Three sediment cores (50 cm depth) were collected at three different sites from a tidal flat estuary at Passagem Channel (Vitória, Espírito Santo State-Brazil) to evaluate the influence of recent urbanization processes on the deposition of organic matter (OM) in a complex polluted tropical estuary. In addition to geochronology (by excess 210Pb), the sources of natural and anthropogenic OM to the sediments were evaluated by total organic C (TOC – 14.29 ± 8.73, 30.43 ± 14.71 and 48.70 mg g−1 ± 25.46, respectively, for P1, P2 and P3), C/N molar ratio and lipid biomarkers (sterols and terpenoids). Taraxerol (3.10 ± 4.85, 9.71 ± 3.85 and 16.10 mg gTOC−1 ± 32.48 for P1, P2 and P3, respectively) and sitosterol (1.71 ± 2.72, 2.94 ± 6.41 and 4.07 mg gTOC−1 ± 4.41 for P1, P2 and P3, respectively) were the most abundant compounds in all cores, suggesting a major contribution of terrestrially-derived OM to the study region. Coprostanol levels and selected sterol index indicated significant contamination by fecal material. The organic geochemical indicators suggest that changes of OM reflect occupation and urbanization alteration processes around the Passagem Channel over the last 70 a, mainly the conversion of mangrove forest into urban areas, bridge building and Treatment Plant Station installation.

The present work evaluate the molecular and isotopic composition of n-alkanes from mangrove species Rizophora mangle (RZ), Laguncularia racemosa (LA) and Avicennia schaueriana (AV) at Mangrove Biological Reserve of Piraquê-Açu and Piraquê-Mirim rivers (Aracruz-ES/Brazil). The n-alkanes total concentrations ranged from 0.89 (R. mangle green leaf) to 398.67 ug.g-1 dry weight (A. schaueriana, senescent leaf), been the senescent leaves having the most abundance independent from specie. The CPI (Carbon Preference Index) values were in the proposed limit for terrestrial plants waxes, where the average between senescent and green leaves from each species were RZ = 6,70; LA = 20,73; and AV = 8,30. The δ13C from C25 to C31 n-alkanes average values indicated a pattern distribution based on saline and hydric stress (L. racemosa = -36.94; R. mangle = -35.98; A. schaueriana = -35.03‰).