Flow-3D CFD model of bifurcated open channel flow: setup and validation

Bifurcation is a morphological feature present in most of fluvial systems; where a river splits into two channels, each bearing a portion of the flow and sediments. Extensive theoretical studies of river bifurcations were performed to understand the nature of flow patterns at such diversions. Nevertheless, the complexity of the flow structure in the bifurcated channel has resulted in various constraints on physical experimentation, so computational modelling is required to investigate the phenomenon. The advantages of computational modelling compared with experimental research (e.g. simple variable control, reduced cost, optimize design condition etc.) are widely known. The great advancement of computer technologies and the exponential increase in power, memory storage and affordability of high-speed machines in the early 20th century led to evolution and wide application of numerical fluid flow simulations, generally referred to as Computational Fluid Dynamics {CFD). In this study, the open-channel flume with a lateral channel established by Momplot et al (2017) is modelled in Flow-3D. The original investigation on divided flow of equal widths as simulated in ANSYS Fluent and validated with velocity measurements

Microplastics in the environment and the analysis:fulfil knowledge gap of research size covering, methodology and analytical technologies

Microplastics (MPs) were initially detected in aquatic environments in the early 2000s. Subsequently, extensive research has been conducted to enhance our understanding of MPs. Nonetheless, information about small MPs remains limited because the majority of studies have concentrated on larger MPs (&gt; 200 μm), and more advanced technologies such as µFTIR imaging still struggle when trying to quantify the smallest of MPs. Additionally, methods are not harmonized, which leads to challenges when comparing data across studies. To address aspects of these questions, this PhD study aimed to analyze MPs down to 10 μm in Danish marine waters. The study also explored the impact of different methodologies on understanding of MPs in the environment. Finally, a novel FTIR detection technology was studied to evaluate its efficacy in detecting small MPs.The study conducted in Danish marine waters revealed that the abundance and mass concentration of MPs convey different information. The abundance of MPs ranged from 17 to 286 items m−3 with an average of 103±86 items m−3, while the mass concentration ranged from 0.6 to 84.1 μg m−3 with an average of 23.3±28.3 μg m−3. The most prevalent types of polymers were polyester, and the majority of the MPs were fragments and small MPs (&lt; 100 μm). Moreover, the study investigated the relationship between MP distribution and human activities, revealing high MP abundance around the Copenhagen-Malmö area, probably due to the population density of the area. In addition, the analysis of the carbonyl index of polyolefins showed significant oxidation of small MPs. A rough mass balance indicated that wastewater and stormwater may play a key role in MPs in introducing MPs to the marine environment.To explore how analytical methodology affect the quantification of MPs in the environment, two different methodologies were employed to analyze the same sample collected from the Danube River, Hungary. The results demonstrated that the analytical methodology used impacted the abundance and mass concentration of MPs. Further investigation revealed that each step in the methodology produced different outcomes, providing insights for future improvement.The study also introduced large area attenuated total reflectance (LAATR)-Fourier-transform infrared spectroscopy (FTIR) applying ZnSe and Ge ATR-units. The use of these units improved the ability to analyze MPs down to 1.3 μm, particularly when detecting small MPs. Moreover, it provided information on both hyperspectral images and the obtained spectra quality, and it assessed criteria for obtaining reliable results with this technique.In summary, this study filled knowledge gaps regarding small MPs in the marine environment, examined the relationship between MP distribution and human activity, and provided insights into the effect of the analytical methodology on MP quantification results. Additionally, the study introduced the application of LAATR-FTIR for detecting small MPs. <br/

A TOOLBOX FOR SEDIMENT BUDGET RESEARCH IN SMALL CATCHMENTS

© 2017, Lomonosov Moscow State University. All rights reserved. Sediment monitoring and assessment remain one of the most challenging tasks in fluvial geomorphology and water quality studies. As a response to various environmental and human disturbance effects, the main sources and pathways of the sediments transported within catchments, especially most pristine small one, may change. The paper discusses state-of-the-art in the sediment budget research for small catchments. We identified nine independent approaches in the sediment transport assessment and applied them in 11 catchments across Eurasia in the framework of an FP-7 Marie Curie-International Research Staff Exchange Scheme in 2012-2016. These methods were classified as: i) Field-based methods (In-situ monitoring of sediment transport;-Soil morphological methods and dating techniques; Sediment source fingerprinting; Sediment-water discharge relationships), ii) GIS and remote sensing approaches (Riverbed monitoring based on remote sensing/historical maps; parametrization of the channel sediment connectivity; Sediment transport remote sensing modeling), and iii) Numerical approaches (Soil erosion modeling and gully erosion (stochastic and empirical models); channel hydrodynamic modeling). We present the background theory and application examples of all selected methods. Linking fieldbased methods and datasets with numerical approaches, process measurements as well as monitoring can provide enhanced insights into sediment transfer and related water quality impacts. Adopting such integrated and multi-scale approaches in a sediment budget framework might contribute to improved understanding of hydrological and geomorphological responses

Do bacteria thrive when the ocean acidifies? Results from an off-­shore mesocosm study

Marine bacteria are the main consumers of the freshly produced organic matter. In order to meet their carbon demand, bacteria release hydrolytic extracellular enzymes that break down large polymers into small usable subunits. Accordingly, rates of enzymatic hydrolysis have a high potential to affect bacterial organic matter recycling and carbon turnover in the ocean. Many of these enzymatic processes were shown to be pH sensitive in previous studies. Due to the continuous rise in atmospheric CO2 concentration, seawater pH is presently decreasing at a rate unprecedented during the last 300 million years with so-far unknown consequences for microbial physiology, organic matter cycling and marine biogeochemistry. We studied the effects of elevated seawater pCO2 on a natural plankton community during a large-scale mesocosm study in a Norwegian fjord. Nine 25m-long Kiel Off-Shore Mesocosms for Future Ocean Simulations (KOSMOS) were adjusted to different pCO2 levels ranging from ca. 280 to 3000 µatm by stepwise addition of CO2 saturated seawater. After CO2 addition, samples were taken every second day for 34 days. The first phytoplankton bloom developed around day 5. On day 14, inorganic nutrients were added to the enclosed, nutrient-poor waters to stimulate a second phytoplankton bloom, which occurred around day 20. Our results indicate that marine bacteria benefit directly and indirectly from decreasing seawater pH. During both phytoplankton blooms, more transparent exopolymer particles were formed in the high pCO2 mesocosms. The total and cell-specific activities of the protein-degrading enzyme leucine aminopeptidase were elevated under low pH conditions. The combination of enhanced enzymatic hydrolysis of organic matter and increased availability of gel particles as substrate supported higher bacterial abundance in the high pCO2 treatments. We conclude that ocean acidification has the potential to stimulate the bacterial community and facilitate the microbial recycling of freshly produced organic matter, thus strengthening the role of the microbial loop in the surface ocean

An assessment of the heavy metal concentrations in the water and sediment of the uMgeni estuary, using visible and near-infrared reflectance spectroscopy.

Masters Degree. University of KwaZulu-Natal, Durban.Abstract available in PDF

Predictive Modeling Of Sinkhole Hazards Using Synthetic Aperture Radar Interferometry (Insar) Subsidence Measurements And Local Geology

The mining of salt domes provides economically important resources through salt and brine production and storage of petroleum products as part of the U.S. Strategic Petroleum Reserve. In order to assess the risk to nearby communities for potential of salt dome collapse, it is important to understand the growth of the Bayou Corne sinkhole and the conditions surrounding the Napoleonville Salt Dome that may have exacerbated its formation. The Bayou Corne sinkhole in Assumption Parish, Louisiana has been expanding since it formed overnight on 2 August 2012. Growing from slightly over 2 acres to more than 30 acres today, the sinkhole has forced the evacuation of approximately 350 local residents and threatens transportation on the nearby Highway 70 hurricane evacuation route. The sinkhole was caused by solution mining of a brine well (Oxy-Geismar Well 3), expanding the subterranean storage cavity too close to the edge of the salt dome. This caused a sidewall collapse into the storage cavity and a rapidly growing sinkhole. The response to the Bayou Corne sinkhole collapse has involved 12 local/state agencies and five federal agencies. The State of Louisiana initiated a $12 million lawsuit against the proprietor of the well, Texas Brine, to recoup much of the State’s costs for response to the sinkhole collapse. The potential for future subsidence in the Bayou Corne area continues to pose a risk to residents. To mitigate this risk, it is important to understand and identify the risk of collapse of caverns on mined salt domes

Effective strategies to manage dredge related threats to tropical seagrass systems based on seagrass ecological requirements

Major dredging projects have the potential to impact on tropical seagrass communities through direct removal and burial and indirectly through turbid dredge plumes reducing the amount of light available to seagrasses. This is a major concern in Australia and elsewhere in the Indo Pacific region where substantial expansion of tropical ports associated with the resources boom is occurring. In the majority of cases managing the impacts from turbid plumes has focussed on a turbidity threshold that has not been related to the true light requirements of the various seagrass species potentially impacted. Here we report on the value of an approach based on determining the minimum light requirements of species, their resilience to impacts and ability to recover and designing a dredge mitigation approach that is focussed on maintaining critical windows of light to support seagrass growth and longer term survival. Results show the value of experimentally determining locally relevant ecological requirements and the importance of understanding the relationships between light requirements, tidal exposure, shifts in spectral quality of light, seasonality and capacity for species to recover from light stress in determining ecologically relevant triggers. This information combined with a robust toolkit for assessing sub-lethal light stress provides an effective dredge mitigation strategy to protect seagrasses