Sediment Plumes Research Articles

Role of Organic Matter Present in the Water Column on Turbidity Flows

Turbidity flows are known to be affected by the density difference between sediment plumes and the surrounding water. However, besides density, other factors could lead to changes in flow propagation. Such a factor is the presence of suspended organic matter. Recently, it was found that flocculation does occur within plumes upon release of a sediment/organic matter mixture in a lock exchange flume. In the present study, mineral sediment (illite clay) was released into the outflow compartment containing water and synthetic organic matter (polyacrylamide flocculant). Even though the density of water was barely affected by the presence of flocculant, flow head velocity was observed to be larger in the presence of flocculant than without. Samples taken at different positions in the flume indicated that flocs were created during the small current propagation time (about 30–60 s) and that their sizes were larger with higher flocculant dosage. The size of flocs depended on their positions in the flow: flocs sampled in the body part of the flow were larger than the ones sampled at the bottom. All these properties are discussed as a function of sediment–flocculant interactions.

In situ optical measurement of particles in sediment plumes generated by a pre-prototype polymetallic nodule collector

This study presents in situ, high-resolution optical measurements of particle size distributions (PSD) within sediment plumes generated by a pre-prototype deep seabed nodule collector vehicle operating in the abyssal Pacific Ocean. These measurements were obtained using a cutting-edge instrument, the LISST-RTSSV sensor. The data collected in situ reveal marked differences compared to previously reported laboratory-based, ex situ measurements. The grain size and other key particle shape characteristics are found to be dependent on multiple factors, including the collector vehicle maneuvers, the time elapsed following sediment discharge, and the complex hydrodynamic processes that generate the sediment in suspension. Significantly, the PSD from a highly complex succession of straight-line maneuvers converges to that of the canonical case of a simple straight-line driving maneuver within a timescale of ten minutes. Our results underscore the importance of parameterizing sediment plume transport models based on well-informed, comprehensive PSDs of detrained suspended sediment measured in situ at adequate timescales and in regions no longer strongly influenced by active and complex hydrodynamic processes.

Developing a dynamic energy budget model to project potential effects of deep-sea mining plumes on the Atlantic deep-sea mussel, Bathymodiolus azoricus

Due to the consistent lack of Environmental Risk Assessment (ERA) for deep-sea mining scenarios, the potential impacts of this industry on marine ecosystems remain largely unknown. In order to fill this gap, a Dynamic Energy Budget (DEB) model was developed to study the consequences of toxic sediment plumes derived from deep-sea mining on the energy budget of the Atlantic deep-sea mussel, Bathymodiolus azoricus. Model calibration was based on environmental conditions observed at the Menez Gwen (MG) vent field (Mid-Atlantic Ridge- MAR), assuming a B. azoricus lifespan of 10 years and a maximum shell length of 119 mm. Scenario simulations were conducted to mimic the effects of increased concentrations of toxic sediment plumes on mussel filtration rates, the absorption of reduced substrates by their endosymbionts, and the energetic costs associated with metal toxicity. Data were sourced from B. azoricus and, when necessary, from proxy species. One disturbance scenario (EF1) incorporated measured rates and realistic parameters, while the other (EF2) was intentionally designed to encompass cumulative effects and uncertainties, representing a potential worst-case scenario. Both disturbance scenarios were initiated at three different timings (0, 1200 and 2400 days) to accommodate the mining effects at different stages of the mussels' life cycle. Results indicate that B. azoricus is significantly impacted by toxic sediment plumes, particularly during earlier life stages, potentially leading to severe growth impairment and mortality. These results were integrated into a food web model of the MG vent field, revealing that disruptions to the energetic balance of the vent mussel have widespread consequences for the entire ecosystem. Overall, we argue that this numerical framework offers a valuable tool for conducting ERA and Environmental Impact Assessments (EIA) in the context of industrial deep-sea mining.

Agitation dredging of silt and fine sand with Water Injection Dredging, Tiamat and Underwater Plough: a case study in the Port of Rotterdam

Abstract Purpose Agitation dredging has gained popularity as an environmentally friendly and cost-effective method for port maintenance. One of the advantages of agitation dredging is the ability to transport sediments out of the port area using natural currents. The effect of the different agitation methods on sediment and water properties has rarely been investigated in a single pilot project. This research aims to study the effects of agitation methods in silt and sand-dominated areas that are frequently maintained. Methods The effects of water injection dredging, (WID) underwater ploughing (UWP) and Tiamat on sediment properties are investigated in the Port of Rotterdam. In-situ measurements and laboratory measurements are carried out to determine changes in the bed level, the particle size distribution of the bed, the turbidity in the water column and the dispersion distance of the sediment plume due to agitation dredging. Results The results of the in-situ monitoring of the agitation pilots allow a comparison of the changes in sediment and water properties before, during and after agitation dredging. The production, advantages and limitations of the tested agitation dredging methods are discussed. Conclusion The in-situ measurements show that WID, Tiamat and UWP can be successfully used for the agitation of sediments and their removal from the silt and sand-dominated areas. The production of the tested agitation methods is higher for silty than sandy sediments. In general, the selection of the agitation equipment can be made based on environmental regulations, sediment properties and hydrodynamic conditions.

Tracing sources of inorganic suspended particulate matter in the Great Barrier Reef lagoon, Australia

Water clarity on the inshore Great Barrier Reef (GBR) is greatly influenced by terrestrial runoff of suspended particulate matter (SPM). Catchment sediment tracing studies often do not extend into the marine environment, preventing the analysis of preferential marine transport. This study employs novel collection and sediment tracing techniques to examine the transport of the terrigenous ‘mineral’ component of plume SPM within the GBR lagoon for two flood events. Utilising geochemical, radionuclide and clay mineral analysis, we trace terrigenous mineral sediments > 100 km from the river mouth. We show that the SPM geochemistry is highly influenced by particle-size fractionation, desorption, and dilution within the plume, rendering traditional tracing methods unviable. However, the ratios of rare earth elements (REE) to thorium (Th) provide stable tracers of mineral SPM transported across the catchment to marine continuum and allow the identification of discrete catchment sources for each flood event. Plume sediment radionuclides are also stable and consistent with sub-surface erosion sources.

Hypoxia Forecasting for Chesapeake Bay Using Artificial Intelligence

Abstract Seasonal hypoxia is a recurring threat to ecosystems and fisheries in the Chesapeake Bay. Hypoxia forecasting based on coupled hydrodynamic and biogeochemical models has proven useful for many stakeholders, as these models excel in accounting for the effects of physical forcing on oxygen supply, but may fall short in replicating the more complex biogeochemical processes that govern oxygen consumption. Satellite-derived reflectances could be used to indicate the presence of surface organic matter over the Bay. However, teasing apart the contribution of atmospheric and aquatic constituents from the signal received by the satellite is not straightforward. As a result, it is difficult to derive surface concentrations of organic matter from satellite data in a robust fashion. A potential solution to this complexity is to use deep learning to build end-to-end applications that do not require precise accounting of the satellite signal from the atmosphere or water, phytoplankton blooms, or sediment plumes. By training a deep neural network with data from a vast suite of variables that could potentially affect oxygen in the water column, improvement of short-term (daily) hypoxia forecast may be possible. Here, we predict oxygen concentrations using inputs that account for both physical and biogeochemical factors. The physical inputs include wind velocity reanalysis information, together with 3D outputs from an estuarine hydrodynamic model, including current velocity, water temperature, and salinity. Satellite-derived spectral reflectance data are used as a surrogate for the biogeochemical factors. These input fields are time series of weekly statistics calculated from daily information, starting 8 weeks before each oxygen observation was collected. To accommodate this input data structure, we adopted a model architecture of long short-term memory networks with eight time steps. At each time step, a set of convolutional neural networks are used to extract information from the inputs. Ablation and cross-validation tests suggest that among all input features, the strongest predictor is the 3D temperature field, with which the new model can outperform the state-of-the-art by ∼20% in terms of median absolute error. Our approach represents a novel application of deep learning to address a complex water management challenge. Significance Statement This study presents a novel approach that combines deep learning and hydrodynamic model outputs to improve the accuracy of hypoxia forecasts in the Chesapeake Bay. By training a deep neural network with both physical and biogeochemical information as input features, the model accurately predicts oxygen concentration at any depth in the water column 1 day in advance. This approach has the potential to benefit stakeholders and inform adaptation measures during the recurring threat of hypoxia in the Chesapeake Bay. The success of this study suggests the potential for similar applications of deep learning to address complex water management challenges. Further research could investigate the application of this approach to different forecast lead times and other regions and ecosystem types.

Flocculation of deep-sea clay from the Clarion Clipperton fracture zone

This article discusses whether or to what extent flocculation plays a role in the saline deep-sea environment and whether sediment plumes generated by deep-sea mining activities are affected by the process of flocculation. The results of our laboratory study demonstrate that deep sea mineral clay with a median floc size of 20μm can flocculate quickly within 2.5 min of mixing to form flocs with a median floc size of about 50–150μm and outliers as large as 500μm in size due to the presence of natural organic matter. At high shear (turbulent mixing), a threshold of about 125s−1 was found above which, organic matter can successfully bind to clay. Above 125s−1, the steady-state floc size is also found to increase linearly with shear. In low energetic conditions (when flocs experience mainly differential settling), the median floc sizes are found to be 2 or 3 times larger than at turbulent mixing. As expected, the rate of flocculation is greater at higher clay concentrations. At long mixing times, the median floc size is found to decrease due to the breaking/reconformation of flocs. Experiments performed to study the ageing of flocs at rest demonstrated that a dynamic process was ongoing between the organic matter and the clay. It is hypothesized that the organic matter present has amphiphilic properties. Over time, the organic matter would rearrange itself such as to maximize its contact area with the mineral clay, resulting in two effects, depending on the structure of the flocs. In the case of flocs formed at high shear, it led to a rupture of flocs. A slow agitation of settled flocs, having previously experienced low shear conditions, on the other hand, led to aggregation. Overall, the results found in the present article show that flocculation likely plays a significant role in deep-sea areas.

Infragravity waves and cross-shore motion–a conceptual study

It is widely known that Infragravity (IG) waves induce cross-shore fluid motion in the nearshore, and multiple recent observational studies have identified IG waves as the dominant factor for a range of nearshore processes such as particle drift in the surf zone, transport of suspended sediment and river plume oscillations. While it is clear that the underlying orbital motion linked to IG wave excursions correlates with IG wave periods, the exact relation between the IG wave amplitude and the strength of the cross-shore motion has not been investigated in great detail. In the present contribution, we aim to quantify the cross-shore motion as a function of the IG wave amplitude. Indeed, it is shown that IG waves of even the most minute amplitude induce a large horizontal movement of particles, and the cross-shore movement is often several orders of magnitude larger than the particle movement induced by ordinary gravity waves. The results hold across a number of situations including monochromatic waves, sea states given by a spectrum as well as nonlinear waves with and without strong bathymetric forcing.

Environmental risk assessment of coastal dredging based on clustering of meteocean forcing

Dredging and dumping in-situ sediments is a fundamental operation for most coastal engineering projects and coastal defense projects, such as the construction of breakwaters, beach nourishment and land reclamation. Future projections in terms of coastal hazard suggest that coastal protection and land reclamation project will be more and more frequent. In this context, the assessment of the environmental and socio-economic impact of the risk induced by dredging is a fundamental step during both the design stage and the operational management. Most of the standard practices and available risk assessment frameworks rely on the numerical prediction of the sediment plume in the large field driven by coastal circulations forced by tides, winds and waves. In this study, we formulated a new risk assessment framework based on an unsupervised machine learning clustering algorithm, K-means clustering, for generating representative meteocean scenarios subsequently used to force a regional circulation model. Moreover, we introduced three criteria of hazard/risk based on the spatial and temporal evolution of the suspended sediment concentration that explained different environmental impacts and two new methods to synthetically present the risk values. The major improvement of the present framework is that the final probability of risk fully describes the statistics in terms of hydrodynamic and dredging conditions.This framework presents the probability analysis of risk spatial distribution based on representative hydrodynamic conditions and dredging scenarios, which is a major improvement of this study compared with previous risk assessment strategies that were unable to predict quantified dredging risk before field construction. Finally, to demonstrate the potentiality of the risk assessment framework, we applied this methodology to the Hong Kong Water and Pearl River Estuary (China) as a pilot case.

Experimental investigation of cohesive soil erosion and suspension caused by a Coandă-effect-based polymetallic-nodule collector

Coandă-effect-based collection stands out as the foremost technology in polymetallic-nodule mining due to the absence of direct contact between the collector and the ocean floor. Yet, this collection method disturbs the ocean floor, and minimizing such disturbance is crucial from an environmental viewpoint. To this end, a solid understanding of the interplay between the collector and the sediment bed is required. Therefore, we carried out a series of small-scale experiments, where a collector drives over a subaqueous clayey bed. These experiments provide the very first quantitative data on cohesive sediment erosion caused by a moving Coandă-effect-based collector, as well as on turbidity currents generated behind the collector head. This paper discusses the observations and findings derived from these experiments. Our findings reveal a logarithmic relationship between erosion depth and the flow impinging force applied on the clayey bed. An increased flow rate in the collection duct results in a slower turbidity current generated behind the collector head. This study enhances the ability to forecast sediment erosion caused by Coandă-effect-based collectors, offering the possibility to optimize the collector operational conditions and minimize the magnitude of the resulting sediment plumes.

Factors influencing the variation of the Sepik-Ramu River system's sediment plume off the north coast of New Guinea

The Sepik-Ramu River system (SRRs) is a principal contributor of terrestrial materials to the pelagic waters of the tropical Western Pacific, boasting the highest sediment discharge in New Guinea. However, this system's sediment outflow and dispersal patterns are not well-documented. This study seeks to address this gap by analyzing the estuarine sediment plumes, which are the key indicators of the marine dispersion of terrestrial materials. Utilizing Moderate Resolution Imaging Spectroradiometer (MODIS) images from 2010 to 2020 and applying the Novoa17 algorithm, we examined the distribution and temporal evolution of the sediment plume of the SRRs estuary. The sediment plume was categorized into two distinct zones: core and diffuse, based on suspended sediment concentration (SSC) levels. Our findings reveal significant seasonal variations of these sediment plumes in the nearshore. The plume area expands during the wet season and contracts during the dry season, respectively, with core and diffuse plumes sharing similar change characteristics. The diffuse plume primarily extends northeast in the wet season and subsequently shifts northwest in the dry season, and the core plume consistently points to the northeast. The study further explores the driving factors and mechanisms behind these patterns, identifying river discharge as the primary influence on the core plume and sea surface winds and coastal currents as determinants of the diffuse plume's behavior. Interannual variations in the plume characteristics were found to be influenced by the El Niño-Southern Oscillation (ENSO), which indirectly affects plume dynamics through its impact on regional precipitation. During El Niño events, characterized by drier conditions and reduced discharge, the plume SSC and area typically decrease. During La Niña events, the plume's SSC and area typically increase, except for the 2011 super La Niña's negative anomaly, caused by the rain belt's excessive westward shift.

Sustained increase in suspended sediments near global river deltas over the past two decades

River sediments play a critical role in sustaining deltaic wetlands. Therefore, concerns are raised about wetlands’ fate due to the decline of river sediment supply to many deltas. However, the dynamics and drivers of suspended sediment near deltaic coasts are not comprehensively assessed, and its response to river sediment supply changes remains unclear. Here we examine patterns of coastal suspended sediment concentration (SSC) and river sediment plume area (RPA) for 349 deltas worldwide using satellite images from 2000 to 2020. We find a global increase in SSC and RPA, averaging +0.46% and +0.48% yr−1, respectively, with over 59.0% of deltas exhibiting an increase in both SSC and RPA. SSC and RPA increases are prevalent across all continents, except for Asia. The relationship between river sediment supply and coastal SSCs varies between deltas, with as much as 45.2% of the deltas showing opposing trends between river sediments and coastal SSCs. This is likely because of the impacts of tides, waves, salinity, and delta morphology. Our observed increase in SSCs near river delta paints a rare promising picture for wetland resilience against sea-level rise, yet whether this increase will persist remains uncertain.

At-sea application of the comet assay to a deep-sea fish

Given the go ahead, deep-sea mining operations are likely to continue for decades on a substantial spatial scale and the resulting sediment plumes combined, are likely to extend beyond the licenced mining areas, and could lead to the chronic exposure of deep-sea organisms to a mixture of metals, even mobile species, such as fish, that could conceivably display avoidance behaviour. The metal concentrations, often substantially below lethal doses, mean that individual mortality is too blunt a measure to allow assessment of “serious harm”. Commonly used cellular biomarkers of exposure in ecotoxicology include DNA damage using the Comet assay. True deep-sea ecotoxicological studies with fish are rare and to our knowledge, there are no published data or method optimizations for deep-sea fish. Coryphaenoides ssp. were collected during SMARTEX expedition 1 (Feb/Mar, 2023) to the Clarion Clipperton Zone (CCZ) in the Eastern Pacific Ocean using a baited trap deployed between 4580–4,732m depth for 24–48 h. Blood and gill tissue were removed and processed for the Comet assay. In order to reduce artefactual DNA damage from cryopreservation observed previously, two sets of samples were prepared: a cryopreservative (10% DMSO) was added to one set of samples and stored at −80 °C; the second set was used to perform a Comet assay within hours of collection. A custom-built gimble table enabled horizontal electrophoresis at sea after which Comet assay slides were dried and stored at room temperature until further analysis. The Comet assay was also assessed in freshly sampled and frozen rainbow trout cells as a proxy control in order to evaluate potential artefacts from the collection and sampling procedure of the deep-sea fish. The blood samples processed at sea had a significantly reduced level of DNA damage compared to the frozen samples. There was no significant difference between the fresh deep-sea and rainbow trout samples. However, the freshly prepared gill samples in Coryphaenoides ssp. showed substantial artefacts, possibly as a consequence of barotrauma. These results represent the first effort at establishing baseline DNA damage data for deep-sea fish, an essential component in understating and quantifying the impact of deep-sea mining.

Real-time water quality forecasting in rivers using satellite data and dynamic models: an online system for operational management, control and citizen science

Increasingly scarce water resources and growing global populations have exacerbated the problems of water quality in river systems and freshwaters in general. New monitoring methodologies and tools to democratize access to water quality information are needed if we are to reach ambitious societal objectives such as the UN Sustainable Development Goals and the European Green Deal. Here we present a cloud-based system for producing publicly accessible real time water quality forecasts coupled to novel biosensor technology. Short term forecasts of water quality impairments, e.g., as cyanobacteria blooms, sediment plumes and toxic pollution incidents are increasingly relevant both to citizens and stakeholders. Here, we present a new cloud based system that utilizes satellite data to produce real time forecasts of flow and water quality using a chain of dynamic catchment-scale models at multiple locations in a river network. We demonstrate this new system using two case studies: the River Thames and the Essex Colne River (United Kingdom). These rivers are key water supply sources for London and South-East England, respectively and are of high interest to recreational water users. We show how the new system can predict and forecast water quality, estimate toxicity and connect to citizen science observations using an App (www.aquascope.com) for information synthesis and delivery.

Bottom and Suspended Sediment Backscatter Measurements in a Flume—Towards Quantitative Bed and Water Column Properties

For health and impact studies of water systems, monitoring underwater environments is essential, for which multi-frequency single- and multibeam echosounders are commonly used state-of-the-art technologies. However, the current scarcity of sediment reference datasets of both bottom backscatter angular response and water column scattering hampers empirical data interpretation. Comprehensive reference data derived from measurements in a controlled environment should optimize the use of empirical backscatter data. To prepare for such innovative experiments, we conducted a feasibility experiment in the Delta Flume (Deltares, The Netherlands). Several configurations of sonar data were recorded of the flume floor and suspended sediment plumes. The results revealed that flume reverberation was sufficiently low and that the differential settling of fine-sand plumes in the water column was clearly detected. Following this successful feasibility test, future comprehensive experiments will feature multi-frequency multi-angle measurements on a variety of sediment types, additional scatterers and sediment plumes, resulting in reference datasets for an improved interpretation of underwater backscatter measurements for scientific observation and sustainable management.

Impact of open-cast placer mining on sediment transport across Far Eastern rivers of Russia

This study examines patterns of sediment transport in Far Eastern rivers of Russia affected by open-cast placer mining—mostly for gold, rarely for silver, and in a few cases for platinum and diamonds. Long-term monitoring and remote-sensing data are used to determine the location of mining landscapes and to detect sediment concentrations and plumes originating from the mining sites. The current study suggests that catchments of the Amur, Kolyma, and Lena rivers are global mining hot spots accommodating up to 1.1%–3.8% of total mining-related vegetation losses. Here, ∼20,100 km of river valleys (0.48% of the river network length) are currently disturbed by mining, with the maximum density of disturbed river valleys being up to 200–300 m/km2 in the basins of the tributaries of the Upper Kolyma and Zeya rivers. To explore the potential mining impact on sediment load, these data were linked with the long-term sediment trends. Concentrations and discharges of mean annual, monthly, and daily suspended sediment decreased from the 1970s and 1980s to the present day at more than 40% of the 40 stream gauge sites assessed across the contiguous Far East. Increasing sediment trends were widespread across 20% of the sites localized in the cluster of greatest mining-related land disturbances. Up to 30% of the sites are characterized by sediment load growth up to the end of the 1980s and a subsequent decline due to the recent abandonment of mining activities. The current study highlights the non-linear relations between mining-related vegetation losses and sediment release into the river network, which is explained by diverse sources of sediment generation within mining areas and other drivers of sediment transport that interact and may attenuate or intensify the signal of mining impact.

Experimental and numerical investigation of the effect of deep-sea mining vehicles on the discharge plumes

During mining activities, deep-sea mining vehicles (DSMVs) are highly susceptible to causing massive disturbance to the seafloor sediment, resulting in the formation of plumes due to underlying turbulence and currents. To gain a better understanding of the dispersion mechanism of sediment plumes, both experimental and numerical methods were employed. The numerical model was primarily used to characterize the solidity and liquidity of the sediment plume through volume of fluid and discrete phase model methods, respectively. The experimental data were validated against the numerical results. The plume distribution was studied in physical experiments for three different DSMV parameters. The study findings indicate that the discharge of the plume in the near field occurs in three stages due to a combination of plume release inertial forces, negative buoyancy in the water column, and wall restoring forces. Additionally, the increase in the travel velocity of the DSMV reduces the propagation of the plume in the direction of discharge and instead increases its lateral spread across the bottom surface. As the size of the DSMV decreases in three dimensions, changes in the vertical vortex structure become dominant in the plume distribution. This leads to a reduction in the length of the plume head and a faster sinking of the plume. When the wake Froude number Frw is between 0.7 and 6.8, representing the wake turbulence effect of DSMV on plume discharge, the diffusion width of the plume on the bottom surface is linearly related to Frw.

Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules, resulting in the creation of plumes that could have a negative impact on the ecological environment. This study aims to investigate the potential solution of using polyaluminum chloride (PAC) in the water jet. The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area. The experimental results showed that the optimal PAC dose was found to be 0.75 g/L. Compared with the test conditions without the addition of PAC, the presence of PAC leads to a reduction in volume, lower characteristic turbidity, smaller diffusion velocity, and shorter settling time of the plume. This indicates that PAC inhibits the entire development process of the plume. The addition of PAC leads to the flocculation of mm-sized particles, resulting in the formation of cm-sized flocs. The flocculation of particles decreases the rate of erosion on the seabed by around 30%. This reduction in erosion helps to decrease the formation of plumes. Additionally, when the size of suspended particles increases, it reduces the scale at which they diffuse. Furthermore, the settling velocity of flocs (around 10−2 m/s) is much higher that of compared to sediment particles (around 10−5 m/s), which effectively reduces the amount of time the plume remains in suspension.

A new countermeasure to deep-sea mining sediment plumes: Using flocculant to enhance particles settling

The sediment plumes produced by deep-sea mining operations have been observed to cause detrimental effects on the ecological environment. However, there is currently no effective measure available to counteract these plumes. In this study, we propose a potential solution to this problem by utilizing flocculants to expedite the settling of particles. Through several experiments investigating the impact of various types and concentrations of flocculants on plumes prepared from sediment samples in potential mining regions, we found that the slow settling velocity of single clay particles leads to the formation of a relatively thick plume suspension layer on a spatial scale, which fails to decay for a considerable period of time, causing turbidity in the water. However, when suitable flocculants are employed, micron-scale sediment particles can be flocculated into centimeter-scale flocs, which significantly increases the settling velocity of the suspended matter. We have identified the appropriate flocculant types and dosages that exhibit optimal efficacy in facilitating the sedimentation of deep-sea sediment particles. Furthermore, our experimental findings have led to the identification of the flocculation mechanism that takes place between deep-sea sediment particles and flocculants. We conducted a comparative analysis of the settling velocity of deep-sea sediment particles both with and without flocculants, which provided additional insight into the promotion of sedimentation by flocculation.

Identification of Gold Mining Vessels based on Classification Algorithms using Sentinel-2 Images

Artisanal and small-scale gold mining can occur on land or in riverbeds. However, the activity needs to be supported by a Mining Permit, issued by the Agência Nacional de Mineração, and the appropriate environmental license from the competent environmental agency. The use of images from Sentinel-2 satellites presents itself as a potential tool for identifying gold mining vessels due to the temporal resolution, free imagery, global coverage, and more refined spatial resolution. So, this study aimed to identify gold mining vessels on the Madeira River near Porto Velho city, Rondônia state, located at Brazilian Amazon, in 13 Sentinel-2 images from 2018 to 2021 using the classifiers: Support Vector Machine (SVM), K-Nearest Neighbors (KNN) Random Forest (RF) and Spectral Angle Mapper (SAM). The results showed that machine learning classifiers obtained the best performance, especially the object-oriented SVM classifier, which had the best average F1 score (0.91). In addition, the detection percentage of gold mining vessels originated by this classifier was satisfactory, with only 0 to 4 active gold mining vessels with sediment plumes being omitted per image. Therefore, based on the results obtained, it was concluded that the use of machine learning classifiers proved to be effective in identifying gold mining vessels.