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In an effort to understand the resuspension phenomena, interactions of spherical micro-meter particles (glass beads (GB) and Stainless steel (SS)) were investigated experimentally on different surfaces (glass, ceramic, hardwood, metal and chemical agent resistant coated metal (CARC)). Particles were deposited on the lower surface of a 10 cm square wind tunnel by gravitational settling. Air flows were imposed from an open entrance at average velocities up to 16 m/s. Individual particle trajectories obtained by high-speed imaging reveal three different types of motion: rolling/bouncing, immediate liftoff and complex motion. Surface roughness significantly affects the particle initial motion prior to liftoff. The majority of particle trajectories from the glass substrate were parallel to the surface with complex motion, covering 25% of the total distance traveled in rolling/bouncing motion before liftoff. Hardwood substrates took the longest time for initial particle movement (t >1 s) causing a more rapid liftoff. The ceramic substrate showed the most rolling/bouncing motion, for 80% of the particles. Additionally, single layer detachment showed that the detachment percentage initially follow an exponentially increasing trend for a period of ~ 1 s, followed by a plateau phase for a period of 5 s. Changing velocity, substrate and particle size significantly affects GB particle detachment. Furthermore, detachment from the metal substrate was consistently higher than the CARC substrates. However, particle density is not a significant difference in the bigger particle size studied. Initial 3-D particle tracking showed that particles seem to travel in a constant angle to the left rather than going straight in the flow direction. A detachment mode model showed that the detachment by direct liftoff required a much higher speed than rolling motion with a minimum of 14 m/s for both GB70 and SS70 on glass and metal surface, and the velocity increased to 21 m/s for the smaller particle. Incorporating the different types of particle motion prior to liftoff into resuspension models, and how their relative contributions change with different particle and substrate materials, can potentially yield improved predictive capabilities.

The research focuses on the various methods that could be used in the laboratory to determine the values of production from a model cutter suction dredge. The values of production obtained from different methods are compared to estimate the best value. The tests were conducted in an attempt to pave the way to find spillage from the cutter suction dredge. The development of these methods is useful for evaluating the sediment spillage and residuals during dredging. The more accurate the values of production the more accurate would be the values of spillage. For this purpose, the laboratory dredge carriage and dredge/tow tank located at the Haynes Coastal Engineering Laboratory at Texas A&M University is used. During the summer of 2007 and 2008, the laboratory dredge carriage was used to dredge sand (d50 = 0.27 mm) in the sediment pit that is 7.6 m (25 feet) long, 3.7 m (12 feet) wide and 1.5 m (5 feet) deep. A laser profiler, a model hopper barge attached with pressure gauges, a flowmeter and density gauge aid in determining the production from the laboratory model of the cutter suction dredge were used. The before and after bathymetry measurements using a laser profiling system are used to determine the amount of sediment remaining after dredging. The hopper is instrumented with pressure gauges to measure the amount of sediment contained in the hopper. The laboratory dredge system has a magnetic flowmeter and nuclear density gauge that provide data to calculate the amount of sand delivered to the hopper. The difference between the sand volume from the before and after bathymetry is the amount of sand that is resuspended and subsequently resettles in the dredging area (residual) and the sand that is not picked up by the dredge (spillage). Many issues in laboratory testing were found during the course of testing and solutions were found. The production values are compared with reasoning as to why the differences occur. The results demonstrate the ability and difficulty of measuring the amount of material that is dredged and the amount of spillage and residuals that occurs during dredging.

A purpose-built cylindrical resuspension chamber (V=0.437 m3 , S=0.35 m2 , S/V=8.38) was used for the dispersion of samples of soil and various kinds of dust. The samples were studied from the point of view of the number and mass distribution of aerosol particles which could affect the concentration of atmospheric aerosol. The samples were taken from lignite, power plant flue ash and from overburden soil in the North Bohemian surface mine Nastup. The individual samples were pneumatically dispersed inside the chamber under defined temperature-humidity conditions (20řC and relative humidity (RH) 50 %). An APS (Aerodynamic Particle Sizer) processing provided us with average size distributions of particle mass and number. Lignite and flue ash probably have the greatest potential impact on the concentration of atmospheric aerosol in the studied locality. The amount of the resuspended mass of the samples varied between 0.001 % (overburden soil) and 0.32 % (mine road). The lignite and flue ash samples were then analyzed by gravimetric methods using the HI (Harvard Impactor) and the SCI (Sioutas Cascade Impactor). The flue ash contained higher amounts of fine particles than the lignite. Subsequent chemical analysis by electron microscope of the filters with deposits of power plant flue ash showed that the PM2.5...

Abstract The goal of this study is to infer the nature of suspended particles from settling, advection, and resuspension processes. Previous studies have not shown that the influence of physical and biogeochemical nature on the behavior of suspended particles. Therefore we expect to observe differential hydrodynamic behavior of suspended particles of different nature in the study. The size distribution of suspended particles is a variable of sediment transport. Size and density, which play a major role in distribution of particles through the water column, are two of primary factors in determining the settling velocity of suspended particles. The sites of the field experiments were located on the Kao-ping Shelf and Kao-ping Submarine Canyon in Southern Taiwan in order to observe resuspension and settling processes. The field experiments were conducted to deploy moored instruments at the two study sites for collecting the time series data. The experiments also included profiling of temporal and special particle and hydrographic parameters along the Kao-ping Submarine Canyon using R/V Ocean Researcher III. In this study we employed a multidisciplinary approach to the study of suspended particles on a plainer inner shelf and sinuous submarine canyon. Base on the observations on the Kao-ping Shelf, the concentration of coarse-grained suspended particles near the bottom was greater than near the surface, and the fine-grained suspended particles was greater near the surface than the bottom. Coarse-grained suspended particles had better correlation with salinity of which nonlithogenic matters were the primary constituents. Fine-grained suspended particles, which consist mainly of lithogenic matters, were affected more by the current. Initial analysis of the data showed that local current speed controlled the distribution of different sizes particles. When strong currents were present, there were more coarse-grained suspended particles. Conversely, there were more fine-grained suspended particles. Regarding the temporal and special observations in the Kao-ping Submarine Canyon, the concentration of suspended particles increased with depth. The compositions of suspended particles measured by LISST-100 and water samples in the submarine canyon showed opposite trends. It revealed that different methods lead to different results. The two sediment trap arrays deployed in submarine canyon were influenced by oscillatory tidal currents. In spring tide there was high concentration of settling particles, which is composed of nonlithogenic materials. Suspended particles in the lower part of the submarine canyon did not all come from the upper part of the canyon but were transported by strong tidal currents to the observed site. The distributions of different sizes particles were the result by different hydrodynamic behavior due to nature of particles. Oscillatory tidal currents could affect the transports of suspended particles from the Kao-ping continental shelf to the Kao-ping Submarine Canyons.

Plankton communities are important members of the food web in coastal systems and are regulated by top-down and bottom-up controls. This study examined the influence of bottom-up controls, such as physicochemical factors, and top-down controls, such as predation, on the plankton communities in South Bay, Texas. Microalgal photopigments were ascertained by high-performance liquid chromatography (HPLC) to determine the relative abundances of major algal classes. Zooplankters were identified to the lowest possible taxon and enumerated. No spatial trends were observed for the physicochemical factors. The northern bay sections exhibited significantly higher phytoplankton and microphytobenthic diatom biomass, probably due to their proximity to the bay inlet. Copepod, gastropod veliger and brachyuran zoea abundances were also higher in this area, albeit insignificantly. The southern bay sections experienced significantly higher cyanobacterial, euglenophyte and chlorophyte biomass, and polychaete larval abundances. Total zooplankton and nauplii abundances were also higher in the southern areas, albeit insignificantly. Sampling the inaccessible areas of the bay in the future may reveal spatial variability among the physicochemical factors which could be influencing the distribution of plankton. Temporal variation for the physicochemical factors followed a typical trend for subtropical climates and influenced the seasonality of the plankton communities. Phytoplankton biomass peaked in February, August and October but these maximums were not significantly different from the other months sampled. Microphytobenthic biomass peaked during the summer months, while diatom biomass also peaked in February. Zooplankton abundances peaked in October, while nauplii and polychaete larvae also peaked in February. Relationships between wind speed, turbidity and the microalgal pigments were assessed to determine if wind-induced resuspension influenced the location of the major algal classes within the water column compared to the sediments. Wind speed and turbidity were directly related to each other, albeit insignificantly. Some phytoplankton and microphytobenthos were considered tychopelagic because wind-induced resuspension increased their biomass in the water column compared to the sediments. The physicochemical factors exerted bottom-up control of plankton community dynamics in this study, while top-down controls, such as predation, require further investigation. Future studies should focus on which of these controls have more influence on plankton community dynamics in South Bay.

Nutrients in the sediments of Lake Manitoba’s south basin are resuspended regularly due to its shallow, polymictic nature. In 2009 short sediment core samples were used to determine an internal available nutrient load from sediment of 17,533 tonnes total nitrogen (TN) and 167 tonnes total phosphorous (TP). Water samples were collected at the Whitemud River and Assiniboine River Diversion (ARD) to determine the N and P input to the lake, resulting in an estimate of a total point source input of 3,547 tonnes of TN and 1,130 tonnes of TP. Open water samples were collected to determine a suspended content of 9.2 tonnes of TN /km2 or and 1.7 tonnes of TP/km2. The ARD is the largest contributor of TP to the south basin. The internal sediment pool is a significant source of TN, and when the ARD does not operate, the largest input of TP to the south basin.

Nutrients in the sediments of Lake Manitoba’s south basin are resuspended regularly due to its shallow, polymictic nature. In 2009 short sediment core samples were used to determine an internal available nutrient load from sediment of 17,533 tonnes total nitrogen (TN) and 167 tonnes total phosphorous (TP). Water samples were collected at the Whitemud River and Assiniboine River Diversion (ARD) to determine the N and P input to the lake, resulting in an estimate of a total point source input of 3,547 tonnes of TN and 1,130 tonnes of TP. Open water samples were collected to determine a suspended content of 9.2 tonnes of TN /km2 or and 1.7 tonnes of TP/km2. The ARD is the largest contributor of TP to the south basin. The internal sediment pool is a significant source of TN, and when the ARD does not operate, the largest input of TP to the south basin.

Zugl.: Wuppertal, Univ., Diss., 2008

La resuspension de sédiments contaminés peut entraîner le relargage d'éléments traces métalliques (ETM) dans la phase dissoute. Pour anticiper le risque de remobilisation des ETM lors de la vidange des retenues de barrages et créer un modèle géochimique permettant de prédire ce risque, des expériences de resuspension de sédiments provenant de trois retenues ont été réalisées pendant une semaine dans un réacteur. Le pH et le potentiel redox ont été suivis en continu et des échantillons ont été prélevés afin de mesurer l'évolution des ETM dissous. Trois grandes tendances d'évolution des ETM ont été mises en évidence et ne sont pas modifiées par les variations des masses de sédiment en suspension (entre 2 et 9 g/L): 1) Cr, Cd et Zn ne sont pas relargués. 2) Mn, Fe Co, Pb, ainsi que As pour deux retenues, augmentent puis diminuent au cours du temps. Ces éléments sont contrôlés par les oxyhydroxydes de Fe et de Mn et l'évolution du potentiel redox dans la solution. 3) Mo, Al, ou As pour une retenue, continuent d'augmenter à la fin des expériences, révélant des processus de relargage plus lents et une stabilisation dans la phase dissoute. Dans les trois retenues, As est l'élément le plus fortement et durablement relargué. Ces données expérimentales ont été utilisées pour calibrer un nouveau modèle géochimique développé par EDF sur ECOLEGO, intégrant la cinétique des réactions d'échange des ETM entre la phase dissoute et trois types de phases solides: les oxydes, les particules organiques et les carbonates. La calibration des paramètres cinétiques permet de bien reproduire les évolutions temporelles des concentrations qui augmentent (relargage) puis diminuent (piégeage). / The resuspension of the contaminated sediments may promote the remobilization of trace metals to the dissolved phase, threatening the water quality. The dam reservoirs sometimes need to be fully drawn down and being able to anticipate the release of the contaminants is essential to improve the management of reservoirs and assess the risk of water quality degradation. Surface sediments were collected in three contaminated dam reservoirs and aliquots of wet sediments were resuspended for a week in a reactor. The pH and the redox potential were continuously measured, dissolved samples were collected and the evolution of dissolved trace elements concentrations were measured. Depending on the elements, different temporal trends can be highlighted during the resuspension experiments. These evolutions were reproducible, regardless of the mass of sediment used from 2 to 9 g/L. 1) Cd, Cr and Zn were not released; 2) Mn, Fe, Co, Pb and As for two reservoirs, increased and then decreased during the experiments and were regulated by the Fe- and Mn-oxyhydroxides and the redox potential; 3) Al, Mo, or As for one reservoir, were still increasing at the end of the experiments, showing slower release processes and the stabilization of these elements under dissolved forms. For theses three reservoirs, As showed the greatest and the most prolonged release during resuspension. The experimental trends of dissolved metals were used in the firts calibration steps of a new chemical speciation model developped by EDF, which takes several kinetic rates into account for the exchange reactions of dissolved metal between water and three types of solid phases.