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The Sepetiba Bay (Southeast Brazil) is a known Cd- and Zn-contaminated site that received spills of a large slag pile leachate from a Zn smelter. With important harbors, Sepetiba Bay demands periodic dredging operations which affect the mobility of the metals. The main goal of this work was to assess metal mobility in sediments and its associated toxicity in a fictive dredging area, to evaluate the risks of the operation. To achieve this goal, 18 superficial sediment samples were collected and characterized for pH and Eh. Sediments were analyzed for grain size, organic carbon, and total nitrogen, and metal mobility was evaluated with a sequential extraction procedure, proposed by the European Community Bureau of Reference (BCR). The results demonstrate that Cd and Zn are mainly associated with the exchangeable fraction (mean concentrations 1.4 mg kg−1 and 149.4 mg kg−1, respectively) and reducible fractions (mean concentrations 0.3 mg kg−1 and 65.5 mg kg−1, respectively), while Fe, Cr, Cu, Ni, and Al were associated with the residual fraction. Metals in the residual fraction are probably associated with the mineral lattice of the sediment and should not represent an environmental risk for the biota. The application of the enrichment factor and three risk assessment indexes (Risk Assessment Code, Risky Pollution Index, and Bioavailability Risk Assessment Index) show that the sediments are considerably enriched in metals that constitute a relevant risk for the sediment biota. In the case of dredging operations, Cd and Zn should be released to the overlying waters and be available to organisms, threatening the whole ecosystem. The proposed approach was shown to be much more precise than what is frequently presented in the Environmental Impact Assessments that only consider the threshold limits of the legislation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mangroves and the associated shoal forest known as ‘restingaʹ are ecosystems of great ecological relevance that play a significant role in the protection of the coastline in tropical regions. In Brazil, the coastal region has been severely affected by urban expansion. The Paranaguá Port, located in Paraná State (Brazil), is the fourth most important Brazilian port in throughput, and is located in an estuarine region which features large mangrove forests. An historical assessment of its inner access channel dredging rates was made to assess the impacts that the expansion of the Port in the last 30 years may have caused to the ecosystem. In the following, the historical data concerning the dredged volume in the inner access channel was compared to the mangrove and the shoal forest associated variation, aiming to establish a potential correlation between vegetation and siltation in the inner access channel to show as the preservation or restoration of specific ecosystems has potential to Nature‐Based Solutions. [ABSTRACT FROM AUTHOR]

Coastal zones support the most productive marine ecosystems, yet they are increasingly threatened by anthropogenic stressors such as dredging. In this study, we investigated how seasonal variation and dredging activities conducted during the construction of a harbor and submarine base (Sepetiba Bay, RJ, Brazil) affected the phytoplankton and zooplankton assemblages. The observed temporal variability at five different sites over 10 years revealed that dredging exceeds the expected influence of dry and rainy seasons on plankton abundance and diversity. In general, the abundance of both groups increased during dredging due to the resuspension of nutrients and benthic organisms. This increase was particularly evident in the dinoflagellate Scrippsiellaa cuminata, the diatoms Thalassiosira rotula and Nitzschia longissima, and the herbivorous zooplankton Acartia clausii and Pseudevadne tergestina. Moreover, season and dredging activities synergistically influenced plankton assemblages, resulting in larger seasonal variations during dredging activities. After the end of the harbor construction, plankton abundance decreased and remained low until the end of the monitoring, which may indicate persistent changes in the biodiversity and ecosystem functioning of impacted areas. [ABSTRACT FROM AUTHOR]

The Gulf of Maranhão, North Coast of Brazil, is one of the regions in the world with largest tidal ranges. The Port Area of Maranhão, in São Marcos Bay, represents the second most important in Brazil. The port facilities are naturally sheltered from swell, with nautical operations and maintenance dredging volumes directly conditioned by macro-tides, which exceed the 6.0 m tidal range, and associated tidal currents, which can reach 7.0 knots. In order to assess the behavior of sea levels in recent decades, in view of the influence of climate changes on tides in various ports around the world, a period of two lunar nodal tidal cycles of 18.61 years, from 1980 to 2017, was investigated using unpublished data recorded in tide gauges. The trend pattern obtained was analyzed statistically and, unlike many other port areas, a sensitive stability of the mean sea level was noted. An important conclusion is about the reduction in HHW and increasing in LLW, leading to a reduction in tidal ranges, in tidal currents and a significant reduction of the shear stress in the bottom, which may increase the dredging rates in the port areas in the next decades, due to an increasing siltation. [ABSTRACT FROM AUTHOR]

Disposal of dredged sediments from harbor areas is often carried out without prior characterization and diagnosis of the benthic ecosystem and its relationships with the physical environment. Geohabitats studies contribute to this previous characterization, showing how geological and geomorphological features are associated with the benthic ecosystems of a given location. To investigate these relationships, acoustic geophysical methods (echobatimetry, sonography, and high-resolution seismic) and direct observation methods (underwater video and geological sampling) were used in two distinct areas on the Rio de Janeiro continental shelf, adjacent to Guanabara Bay: Area I (degraded with dredging disposal) and Area II (control, without disposal). After the acquisition, processing, and integrated data interpretation, it was possible to determine 5 (five) classes of geohabitats: class I, areas with high acoustic reflectivity, with little or any presence of benthic organisms, under the direct influence of discarded material; class II, areas of high acoustic reflectivity, with predominance of quartzose sand mixed with calcareous fragments (shells), with abundance and diversity of benthic organisms; class III, areas of very high acoustic reflectivity (backscattering), with high abundance and diversity of benthic organisms, indicative of semi-consolidated seafloor (articulated algal "reefs"); class IV, areas with high acoustic backscattering, with strong presence of bed forms (megaripples), associated with the quartzose sand; and class V, areas of low acoustic reflectivity, with sand-muddy textures, low abundance, and relative diversity of benthic organisms. It was verified that the use of these noninvasive GEOHAB techniques had an excellent correlation between the obtained results and proved to be an important tool for the characterization of Geohabitats in areas of dredge sediment disposals on Rio de Janeiro continental shelf, adjacent to Guanabara Bay—Brazil. [ABSTRACT FROM AUTHOR]

This study aims to employ a combination of numerical models to simulate bed evolution under various operational strategies within two navigation channels in Mirim Lagoon, Brazil. The model simulations accurately represent the water levels within the lagoon. These findings suggest that river discharge plays a pivotal role in shaping the temporal patterns of sediment transport within the system. The morphodynamic model reveals that sediment transport and bed evolution primarily occur in a southwest-to-northeast direction, following the flow of water. The greatest sediment accumulation is observed in the central and southern regions of the lagoon. Our results confirm that channel dredging induces significant variations in lagoon physical parameters, such as current velocity. The bed evolution results indicate that rapid siltation of the channel follows dredging, suggesting a substantial increase in bottom evolution within the navigation channels compared to the unaltered scenario. Our findings highlight that the utilization of hydromorphodynamic modeling, with a particular emphasis on dredge-and-dump strategies, can serve as a precise methodology to enhance natural mechanisms that positively influence channel depth and stability. This approach also enables us to predict unfavorable changes in physical parameters over both the medium and long term. • The TELEMAC-MASCARET system coupled is used to simulate sediment transport and dredging/dumping process for five years. • The tributaries' discharges mainly control the temporal patterns of sediment transport in the system. • The sediment transport occurred in the southwest to northeast direction, following the main flow direction. • The sediments mainly accumulate in the central and southern regions of the lagoon. • The results affirm that dredging of the channels causes significant variations in the lagoon's physical parameters. [ABSTRACT FROM AUTHOR]

Tropical marine environments are rich in biodiversity and the presence of harbor activities in these areas can harm the coastal ecosystems. In this study, we assessed sediment quality of two harbors from a tropical region in Brazil by applying multiple lines-of-evidence approach. This approach included the integration of results on: (1) grain size, organic matter, organic carbon, nitrogen, phosphorus, trace metals, polycyclic aromatic hydrocarbons, linear alkylbenzenes, and tributyltin; (2) acute toxicity of whole sediments and chronic toxicity of liquid phases; and (3) benthic community descriptors. Our results revealed that the main contaminants detected in sediments from Mucuripe and Pecém Harbors were chromium, copper, nitrogen, zinc, and tributyltin. These toxicants arise from typical harbor activities. However, the changes in benthic composition and structure appear to depend on a combination of physical impacts, such as the deposition of fine sediments and the toxic potential of contaminants, especially in Mucuripe. Thus, apart from toxicants physical processes are important in describing risks. This information may assist in management and conservation of marine coastal areas. [ABSTRACT FROM AUTHOR]

Dredging activities cause sediment resuspension, which can change the bioavailability of nutrients such as phosphorus (P) in aquatic ecosystems due to remobilization. This study evaluated the remobilization of P in the solid and dissolved phase before and after sediment resuspension in the Meriti and Iguaçu River estuaries and the Rio de Janeiro and Niterói harbor in Guanabara Bay (Rio de Janeiro, Brazil). Three water and sediment samples were collected at each point. Dissolved phosphorus (DP), total phosphorus (TP), organic phosphorus (OP), and inorganic phosphorus (IP) were analyzed before and after resuspension. Resuspension directly impacted the fine-grained samples, causing the release of P into the water column after resuspension, increasing eutrophication of the estuary and risk to biota. The phosphorus enrichment index (PEI) was calculated in the four areas, and in all areas, the index was above 1, which means high ecological risk. The area with sandy granulometry and a lower percentage of organic matter showed an increase in the index after resuspension. The resuspension may impact the increase of eutrophication in some areas, due to the remobilization of the sediment and the adsorbed contaminants., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

We assess changes in estuarine hydrodynamics due to the deepening of navigation channels by dredging. A validated numerical hydrodynamic model (Delft3D) was used to analyze scenarios (historical bathymetry data from 1876 to 2014) and applied to assess the hydrodynamic evolution of the Santos estuarine system (SES), Brazil. During the studied period, the SES underwent significant morphological changes, mainly related to the dredging of the Santos harbor navigation channel. The unprecedented results of the hydrodynamic evolution of the SES show that the gradual process of deepening the channels by dredging resulted in modified estuarine circulation parameters such as tidal propagation and stratification of the water column, as well as the residual water and materials transport through the SES channels. Channel deepening resulted in greater saline intrusion, a decrease in the volume of water transported through the Santos channel, an increase in the influence of the tide in the system and an increase in its asymmetry over the years in the upper estuary. • We assess changes in estuarine circulation by the deepening of channels through dredging. • A validated hydrodynamic model (Delft3D) was used to analyze morphological scenarios. • Gradual deepening of the channels resulted in local changes in estuarine circulation. • Tidal propagation and water column stratification are modified. • Residual water transport through the estuarine channels is changed. [ABSTRACT FROM AUTHOR]

Knowledge of the difficulties, costs, and territorial issues surrounding fishing communities seems crucial to achieve sustainable development goals in marine and coastal zones. However, such knowledge is not always available, sufficient, or even identifiable. The seabob-shrimp small-scale fisheries in the shallow waters of the State of São Paulo, in Southeastern Brazil, plays an important role in coastal livelihoods, providing social and economic benefits for a number of local communities and a premium source of regional seafood. Around 4000 fish-workers produce supplies for restaurants, fishmongers and supermarkets in coastal towns with about 2 million inhabitants. Nevertheless, harbor and naval mooring, the construction of pipelines, sewage disposal, controversial seasonal closures, and marine spatial zoning have all restricted the activity. A territorial approach is here proposed to examine the timeline of vertically implemented laws/regulations that may have resulted in a decrease of territories formerly available to that fisheries, accompanied by a comprehensive outlook of the overall policy context. The shrinkage of fishing territories has been evidenced and the kind of territorial loss detected does not seem to be implicit in cost analysis of fisheries, ecosystem services, or compensation. Top-down policies and a misunderstanding of environmental mitigation programs appear to have been contributing to increasing conflicts, mining multi-stakeholder processes and social justice in contrast to the ascendant economic growth of both the oil and gas and port industries. While economic and political pressures seem to shape current fishing territories, the recognition of the diversity of interests and power asymmetries in coastal zones directs our attention to a vital, often ignored, dimension of social reality. Institutional challenges and recommendations, such as territorial use rights and legal innovations are discussed, adding value to the self-organization of local communities for an effective process of balanced power both within and outside legal marine protected areas. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Oceanography is the property of Instituto Oceanografico da Universidade de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights: [•] Dredging may present a risk to the environment in a southern Brazil estuary. [•] Ammonia present in sediment was responsible for more than 40% of the toxicity. [•] There is evidence of the disposal of sediments in the contamination of the coastal. [ABSTRACT FROM AUTHOR]

Little is known about the diversity of non-geniculate coralline red algae (Rhodophyta, Corallinophycidae) from deep waters in Brazil. Most surveys undertaken in this country have been carried out in shallow waters. In 1994, however, the REVIZEE program surveyed the sustainable living resources potential of the Brazilian exclusive economic zone to depths of 500 m. In the present study, the rhodolith-forming coralline algae from the continental shelf of Espírito Santo State were identified. Samples were taken from 54 to 60 m depth by dredging during ship cruises in 1997. Three rhodolith-forming species were found: Spongites yendoi (Foslie) Chamberlain , Lithothamnion muelleri Lenormand ex Rosanoff and Lithothamnion glaciale Kjellman. These records extend the distribution ranges of these species into Brazilian waters and extend the depth distribution of non-geniculate coralline red algae into Brazilian water to 58 m. [ABSTRACT FROM AUTHOR]

Copyright of Brazilian Journal of Oceanography is the property of Instituto Oceanografico da Universidade de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Brazilian Journal of Oceanography is the property of Instituto Oceanografico da Universidade de Sao Paulo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background, aim, and scope Contaminated sediments are a worldwide problem, and mobilization of contaminants is one of the most critical issues in environmental risk assessment insofar as dredging projects are concerned. The investigation of how toxic compounds are mobilized during dredging operations in the channel of the Port of Santos, Brazil, was conducted in an attempt to assess changes in the bioavailability and toxicity of these contaminants. Materials and methods Bulk sediment samples and their interstitial waters and elutriates were subjected to chemical evaluation and ecotoxicological assessment. Samples were collected from the channel before dredging, from the dredge's hopper, and from the disposal site and its surroundings. Results The results indicate that the bulk sediments from the dredging site are contaminatedmoderately with As, Pb, and Zn and severely with Hg, and that polycyclic aromatic hydrocarbon (PAH) concentrations are relatively high. Our results also show a 50% increase in PAH concentrations in suspended solids in the water collected from the hopper dredge. This finding is of great concern, since it refers to the dredge overflow water which is pumped back into the ecosystem. Acute toxicity tests on bulk sediment using the amphipod Tiburonella viscana showed no toxicity, while chronic tests with the sea urchin Lytechinus variegatus showed toxicity in the interstitial waters and elutriates. Results are compared with widely used sediment quality guidelines and with a sediment quality assessment scheme based on various lines of evidence. Conclusions The data presented here indicate that the sediments collected in this port show a certain degree of contamination, especially those from the inner part of the channel. The classification established in this study indicated that sediments from the dredged channel are impacted detrimentally and that sea disposalmay disperse contaminants. According to this classification, the sediments are inappropriate for disposal at sea. It should be emphasized that the poor quality of fine sediments discharged from the hopper dredge in the overflow process can recontaminate the environment. Recommendations and perspectives These findings will help to underpin improved planning of management strategies for dredging operations and sediment disposal in Brazil and other countries. [ABSTRACT FROM AUTHOR]

The purpose of this research was to assess the effects of dredging performed in a marginal wetland colonized by aquatic macrophytes on eutrophication of the adjacent shallow tropical lake (Imboassica Lake, Brazil). The river mouth of the Imboassica River that drains into hnboassica Lake had been densely colonized by aquatic vegetation dominated by Typha domingensis (Pers.) when it was dredged. Total and dissolved nitrogen and phosphorus concentrations were measured monthly over 13 years at four stations in the Imboassica river-lake system. Dredging activities reduced phosphorus and nitrogen retention at the river mouth and subsequently increased these nutrient stocks in the lake waters. Nutrient retention by non-dredged wetland was estimated to be ca. 1,200 kg year-1 (87.3 g m-2 year-1) for nitrogen and 60 kg yea-1 (4.5 g m-2 year-1) for phosphorus. Our whole-lake approach suggested that dredging might intensify rather than mitigate eutrophication in shallow tropical lakes when the removal of aquatic macrophytes is coupled to the persistence of anthropogenic nutrient inputs from the watershed. [ABSTRACT FROM AUTHOR]

Sediment re-suspension experiments have been conducted to predict contaminants release from sediments to the water column, during dredging operations. In this context, polluted, anoxic estuarine sediments from Rio de Janeiro, SE Brazil, were suspended in oxygenated estuarine water, in laboratory experiments intended to simulate their dispersion by flood flow or dredging operations, in order to measure any release into solution of heavy metals originally present as sulphides that might suffer oxidation. Oxidation of sulphides to sulphate acidified the waters but only after at least 5 h of suspension. Furthermore, the oxidation of acid volatile sulphide (AVS) to sulphate was more rapid and only proceded to completion within 5 days, when large quantities of sulphide forming metals other than Fe were not present. In sediment heavily polluted with zinc, oxidation of AVS was slower and incomplete, resulting in soluble release of a much smaller fraction of the Zn present in the sediment and a maximum dissolved zinc concentration that was much lower than that resulting from less contaminated sediment. The maximum percentages of sulphide-bound metals appearing in solution at any time during re-suspension were low, less than 46% in all cases and typically less than 10%. These maxima were manifested only after acidification by sulphate formation. Appreciable metal dissolution would not occur in an estuary if dilution and dispersion separated the sediment from acid generated or if dredged material settled before acidification occurred. [ABSTRACT FROM AUTHOR]

The Paranaguá Bay is located on the center-north littoral of the state of Paraná in the south of Brazil. Three natural channels give access to the Atlantic Ocean, denominated as North and Southeast (north of Mel island) and Galheta channel (south of the same island). The last one is the main access to the Paranaguá port, where maintenance dredging activities are necessary for navigation. This study aims to characterize the channel morphological variations from 1972 to 2000. It is our goal also to quantify the sedimentation rates for some critical sections of the channel and to understand the processes of sediment transport along the southern mouth of the bay. The wave front arrives preferentially from southeast, and the alongshore drift of the coastal sediments is toward the northeast. The alongshore sediment flux on the Paranaguá Bay mouth vicinities is characterized by two main fluxes: (1) on the external sector, one contours the terminal lobe of the ebb-tidal delta, deflecting the channel to the northeast. In spite of the rectification attempts, by dredging, channel deflection has persisted through the past decades. (2) On the inner sector, the sediment flux moves up the estuary, along the margin of the Pontal do Sul coastal village, being redirected by the ebb-tide currents proceeding from the Cotinga channel, to the Galheta channel. The tidal currents lose energy on the widest portion of the estuary, and the sediments are deposited there, forming an inner bank. Sedimentation rates calculated for the external sector varied between 19.3 and 229.2 x 10³ m³/mo, but a larger data set is necessary, for the confirmation of this pattern of channel shoaling. [ABSTRACT FROM AUTHOR]

The paper discusses the geo-environmental studies carried out to revitalise a silted up channel in Guanabara Bay. A dredging operation has been planned to remove about 1.5 million cubic meters of contaminated sediment. Investigations were performed to characterise the sediment in terms of its physical and chemical properties and to evaluate the presence of heavy metals and organic compounds, particularly polycyclic aromatic hydrocarbons PAH. Finally, dredging and disposal schemes are briefly outlined based on measured contamination levels. [Copyright &y& Elsevier]

N. Mirlean, L. Calliari, and K. Johannesson examined the REE paired La/Eu and Gd/Yb ratios in the region of Patos Lagoon estuary/Brazil and related coastal waters. They concluded that " the mud deposition events at the beach were most likely associated with dredging processes in the estuary especially where overflow is the source of fluid mud on the beach shoreface ". In this response to that study, we reflect on several discrepancies in their methods, results and conclusions. In this work, we demonstrate that the approach adopted by the authors does not provide evidence that the selected REE ratios measured on muddy deposits on the beach were derived from dredged activities, particularly regarding overflow. On the contrary, based on their results, the REE ratios presented in the suspended sediments collected in the navigation channel are most likely associated to natural sediments. [ABSTRACT FROM AUTHOR]

Management of estuarine systems under anthropogenic pressures related to port settlement and development requires thorough understanding about the long-term sediment dynamics in the area. In an era of growing shipping traffic and of ever larger ships; millions of tons of bottom sediments are dredged annually all over the world and the major question concerning dredging operations is not whether they should be done, because it is obvious that they are extremely important and necessary, but where the dredged sediments can be disposed of with the least possible ecological impact. The present study involves the evaluation of transport trends of dredged material from a turbid estuary disposed of in four different open ocean disposal sites using numerical model techniques, aiming to contribute to minimizing potential environmental impacts and maximizing efficiency of the dredging operation. The study is carried out in southern Brazil, investigating the fate of dredged material from the Port of Rio Grande, located inside the Patos Lagoon estuary. Simulations were carried with the TELEMAC-3D model coupled with the suspended sediment (SEDI-3D) module and incorporating results from the wave module (TOMAWAC) to evaluate the dispersion of the suspended sediment plume and its interaction with coastal currents. This modeling structure proved to be a valuable tool to study the hydrodynamics and sediment transport pathways in estuarine and coastal areas. Results indicate that the natural Patos Lagoon coastal plume was observed under the predominant ebb flows and NE winds, promoting fine sediment entrapment south of the mouth of the lagoon (in front of Cassino Beach). The dispersion plumes in the disposal sites responded to the wind intensity and direction and did not present any transport tendency towards Cassino Beach. Part of the dredged sediment disposed of in the proposed alternative sites located in deeper areas (Sites B and C) left the site and was transported parallel to the coast (SW–NE direction) according to the wind direction (NE–SW). The area where the disposal sites were located took around 4 days to recover from the dredging operation and reach the usual suspended sediment concentrations and the actual Port of Rio Grande Licensed Site for dredged material proved to be the best alternative among the investigated options. [ABSTRACT FROM AUTHOR]

Sediment dredging impacts coastal environments by promoting the resuspension of fine particles and remobilization of contaminants that may trigger toxic effects. In this study, we evaluated the sediment quality in harbor areas of Mucuripe bay, a semi-arid ecosystem located in Ceará state (Brazil), which is subject to dredging activities. A sampling survey was conducted right after dredging operations and data compared to another survey performed prior dredging. Sediments were analyzed for fine particles, organic carbon, nutrients, metals, hydrocarbons, and tributyltin (TBT). Toxicity of whole-sediment and liquid phase exposures were also determined. The concentrations of Cd, Cr, Cu, and Zn decreased after dredging, which was confirmed by the geoaccumulation index. Levels of TBT dropped while phosphorus, aliphatic and polycyclic aromatic hydrocarbons increased. Toxic effects persisted, indicating a post-dredging recontamination combined with other sources such as urban runoff, wastewater discharges, harbor activities, and antifouling particles. Data from Mucuripe and Pecém harbors were compiled and site-specific sediment quality values (SQVs) were developed by using multivariate methods. The threshold values proposed by our study were lower and more effective to predict toxicity compared to international guidelines, indicating levels of contamination for this tropical region in which toxic effects may occur. Considering the large geographic area with different sediment characteristics of the Brazilian coast, this study represents a significant contribution to sediment toxicity assessment of dredging activities in semi-arid environments. Image 1 • Data on sediment quality of harbor areas in a Brazilian semi-arid region were analyzed. • Remobilization and reduced levels of contamination were observed after dredging activities. • Site-specific sediment quality values were developed by using multivariate methods. • Threshold values were more effective to predict toxicity compared to international guidelines. [ABSTRACT FROM AUTHOR]

Deposits of fluid mud on wave-dominated beaches are rare. Where they happen frequently and periodically, they can be associated with anthropic processes that bring fluid mud to the shoreface and surf zone. To determine the reason for the frequent deposition of fluid mud at Cassino Beach (Southern Brazil) in the 2014-2020 period, the La/Eu and Gd/Yb ratios in marine, beach, and adjacent Patos estuary sediments were investigated. Mud from the beach showed similar ratios of REE to dredged sediments from the harbor basin and navigation channel within the estuary. Industrial and port activity changes REE ratio in sediments of the navigation channel, and they are distinct from naturally deposited marine and estuarine sediments. We conclude that the mud deposition events at the beach are most likely associated with dredging processes in the estuary especially where overflow is the source of fluid mud on the beach shoreface., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

(1) Although suffers from intense pollution inputs, Guanabara Bay, the most socioeconomically and environmentally important estuary in Rio de Janeiro, Brazil, is still home to a diverse fauna, including several fish and crab species consumed by humans. The bay presents high sedimentation rates and sediment contamination, further aggravated by dredging processes carried out in recent years. In this context, this study aimed to verify the effect of the dredging process on total mercury (THg) concentrations at Guanabara Bay through swimming crab assessments sampled before (2016), during (2017), and after (2018) the dredging process, and mainly, if the detected concentrations can be harmful to consumer health; (2) Methods: Swimming crab samplings were carried out at the same time and sampling points in 2016, 2017 and 2018 and the total Hg was determined using a Direct Mercury Analyzer (DMA-80, Milestone, Bergamo, Italy); (3) Results: Increased Hg concentrations were observed during the dredging process, decreasing to lower values, close to the initial concentrations, at the end of the process. Some of the investigated abiotic factors favor Hg dynamics in the aquatic environment, while others were positively altered at some of the assessed sampling areas at the end of the dredging process; (4) Conclusions: Although crab Hg levels were below maximum permissible limits for human consumption, it is important to note that these animals are significantly consumed around Guanabara Bay, which may lead to public health issues in the long term.

Many estuaries present natural harbor conditions with relatively calm and shallow waters that provide a connection between the ocean and continental waterways. The increase in the demand for goods by the constant growing of the world population has forced estuaries to be altered by human activities, such as dredging, in order to maintain a safe navigation system. The development of sophisticated morphological and hydrodynamic models opened a new perspective of assisting dredging operations inside different estuaries. Thus, the aim of this study is to apply a hydromorphodynamic model to simulate the bed evolution of the Patos Lagoon estuary, southern Brazil. The results of the simulation were applied in a dredge operation model to simulate dredging inside the waterway of the Rio Grande harbor, located inside the Patos Lagoon estuary. The salinity and current velocities inside the estuary were well represented by the model simulations. An annual mean discharge of 3 407 ms3 s−1 was calculated for the lagoon for the year 2004. The morphodynamic model successfully represented the silted and eroded scenarios for the estuarine channel. The dredge operation model results affirm that dredging of the channel causes significant variations in estuarine physical parameters such as salinity, current velocity and suspended sediment concentration. The bed evolution results indicate that a fast siltation of the channel occurs right after dredging stops, stabilizing the variations after a 60-day period. • Silted areas were identified by the morphodynamic model. • Dredge polygons were defined over the silted areas. • The dredging model was applied on the dredge sectors defined. • Current velocities presented considerable reduction on a dredged scenario. • The results indicate intense siltation of the dredged areas until 60 days after the end of the operations. [ABSTRACT FROM AUTHOR]

Sediments represent complex mixtures and the impacts of their physical and chemical processes on biota are important for assessing potential health risks. We aimed to rank sediment samples from Guanabara Bay by developing an algorithm (quality ratio-QR), focusing on key sediment parameters (fine grain size, total organic carbon (TOC), metal concentrations) and enzymatic activities (dehydrogenase (DHA-energy production into cell) and esterases (EST-hydrolase organic matter outside the cell membrane)) of in situ microbial communities. Our QR is supported by quantitative information and significant correlations between geochemical and microbial processes. The QR is a function of the dependent term DHA/EST and the geochemical term (TOC×∑CF)/fine-grained sediment, where ∑CF is the sum of contamination factors (ratio between actual and background metal concentrations). We could rank our sampling sites into three risk classes based on QR: low, medium, and high. Our findings suggest altered homeostasis due to the development of contamination resistance. We applied a sensitivity analysis, using Brazilian law for sediment quality assessment, to calibrate our risk index. Our QR is suitable for measuring the potential health risk of any sediment, especially in developing countries with serious technical limitations, since its evaluated parameters are cheap, fast, and easy to obtain.

Reports on the deepening project for the River Tiete in Sao Paulo, Brazil. Companies involved in the project; Reasons for the deepening project; Measurement of the planned increase for the river's depth.