scholarly journals Processes and Mechanisms of Phosphorus Mobility Among Sediment, Water and Cyanobacteria Under Hydrodynamic Conditions

2021 ◽  
Author(s):  
Lingxiao Ren ◽  
Keqiang Ding ◽  
Zhixin Hu ◽  
Huiya Wang ◽  
Ning Qi ◽  
...  
Keyword(s):  
Laboratory Experiments ◽  
Natural Waters ◽  
Sediment Resuspension ◽  
Algal Growth ◽  
Natural Ecosystems ◽  
Overlying Water ◽  
Close Relationship ◽  
Study Laboratory ◽  
Total P ◽  
Accumulation Ability

Abstract Phosphorus (P) has an important role in eutrophication and it is essential to explore the processes and mechanisms of P mobility in natural waters. In this study, laboratory experiments were conducted to simulate the SW system (sediment and water) and SAW system (sediment, algae and water) under four hydrodynamic intensity conditions (static control, 50 rpm, 125 rpm and 200 rpm treatments), to investigate P mobility. Results in SW system showed that, sediment was an important source of P for overlying water, and the released total P (TP) increased with stronger hydrodynamic intensity, when P associated with metal pools (redox-sensitive P [BD-P] and meta-oxides bound P [NaOH-P]) were the most unstable and easier to migrate into the overlying water. Stronger hydrodynamic disturbances could enhance the processes including sediment resuspension, dissolution of particles, and release of P, when P mobility had a close relationship with redox conditions near sediment-water interface (SWI). Therefore, the release of TP, BD-P and NaOH-P from sediment increased and decreased in the control and 50-200 rpm treatments over time. In SAW system, the release of TP significantly increased from sediment comparing to SW system, and the growth of Microcystis aeruginosa could selectively enhance the release of BD-P, NaOH-P, and organic P (OP). Meanwhile, the released P from sediment was quickly accumulated by algal cells. The maximum accumulation ability of P by cells, the highest photosynthetic efficiency and the best growth of M. aeruginosa were observed in 125 rpm treatment. But with excessively strong hydrodynamic intensity (200 rpm treatment), the accumulation ability of P and alkaline phosphatase activity (APA) of M. aeruginosa was suppressed, which might hinder algal utilization of P and inhibit algal growth. Overall, our findings demonstrated the patterns of P mobility in natural ecosystems and could contribute to the understanding of P cycling.

Phosphorus Leaching Under Cut Grassland

1999 ◽  
Vol 39 (12) ◽  
pp. 63-67 ◽  
Author(s):  
B. L. Turner ◽  
P. M. Haygarth
Keyword(s):  
Surface Waters ◽  
Large Scale ◽  
Agricultural Land ◽  
Algal Growth ◽  
Soil Types ◽  
P Fractions ◽  
Inorganic P ◽  
Potential Source ◽  
Significant Mechanism ◽  
Total P

Phosphorus (P) transfer from agricultural land to surface waters can contribute to eutrophication, excess algal growth and associated water quality problems. Grasslands have a high potential for P transfer, as they receive P inputs as mineral fertiliser and concentrates cycled through livestock manures. The transfer of P can occur through surface and subsurface pathways, although the capacity of most soils to fix inorganic P has meant that subsurface P transfer by leaching mechanisms has often been perceived as negligible. We investigated this using large-scale monolith lysimeters (135 cm deep, 80 cm diameter) to monitor leachate P under four grassland soil types. Leachate was collected during the 1997–98 drainage year and analysed for a range of P fractions. Mean concentrations of total P routinely exceeded 100 μg l−1 from all soil types and, therefore, exceeded P concentrations above which eutrophication and algal growth can occur. The majority of the leachate P was in algal-available Mo-reactive (inorganic) forms, although a large proportion occurred in unreactive (organic) forms. We suggest that subsurface transfer by leaching can represent a significant mechanism for agricultural P transfer from some soils and must be given greater consideration as a potential source of diffuse P pollution to surface waters.

Mechanisms responsible for the niche shift of brook charr, Salvelinus fontinalis Mitchill, when living sympatrically with creek chub, Semotilus atromaculatus Mitchill

1984 ◽  
Vol 62 (8) ◽  
pp. 1548-1555 ◽  
Author(s):  
Pierre Magnan ◽  
Gérard J. FitzGerald
Keyword(s):  
Laboratory Experiments ◽  
Salvelinus Fontinalis ◽  
Niche Shift ◽  
Intraspecific Aggression ◽  
Brook Charr ◽  
Semotilus Atromaculatus ◽  
High Level ◽  
Gill Raker ◽  
Creek Chub ◽  
Study Laboratory

When brook charr, Salvelinus fontinalis Mitchill, are in allopatry in oligotrophic Québec lakes, they feed largely on macrobenthic invertebrates. However, when brook charr cooccur with creek chub, Semotilus atromaculatus Mitchill, they feed largely on zooplankton. In the present study, laboratory experiments showed that creek chub were more effective than brook charr in searching for hidden, patchily distributed prey. The searching efficiency of an individual chub feeding in a group was improved through social facilitation. In contrast, the high level of intraspecific aggression observed in brook charr prevents the formation of such feeding groups. In the laboratory, brook charr were able to displace creek chub from the food source because of interspecific aggression. Data are presented showing that chub are morphologically better adapted than charr to feed on benthos (subterminal orientation of the mouth and protrusible premaxillae), while the charr are better adapted than chub to feed on zooplankton (gill raker structure). Differences in feeding behaviour, morphology, and relative abundance between these species appear to be important in the observed niche shift of brook charr in nature.

Electricity generation through a photo sediment microbial fuel cell using algae at the cathode

2017 ◽  
Vol 76 (12) ◽  
pp. 3269-3277 ◽  
Author(s):  
B. Neethu ◽  
M. M. Ghangrekar
Keyword(s):  
Power Generation ◽  
Organic Matter ◽  
Microbial Fuel Cells ◽  
Carbon Capture ◽  
Algal Growth ◽  
Oxygen Demand ◽  
Sediment Organic Matter ◽  
Overlying Water ◽  
Organic Matter Removal ◽  
Removal Efficiencies

Abstract Sediment microbial fuel cells (SMFCs) are bio-electrochemical devices generating electricity from redox gradients occurring across the sediment–water interface. Sediment microbial carbon-capture cell (SMCC), a modified SMFC, uses algae grown in the overlying water of sediment and is considered as a promising system for power generation along with algal cultivation. In this study, the performance of SMCC and SMFC was evaluated in terms of power generation, dissolved oxygen variations, sediment organic matter removal and algal growth. SMCC gave a maximum power density of 22.19 mW/m2, which was 3.65 times higher than the SMFC operated under similar conditions. Sediment organic matter removal efficiencies of 77.6 ± 2.1% and 61.0 ± 1.3% were obtained in SMCC and SMFC, respectively. With presence of algae at the cathode, a maximum chemical oxygen demand and total nitrogen removal efficiencies of 63.3 ± 2.3% (8th day) and 81.6 ± 1.2% (10th day), respectively, were observed. The system appears to be favorable from a resources utilization perspective as it does not depend on external aeration or membranes and utilizes algae and organic matter present in sediment for power generation. Thus, SMCC has proven its applicability for installation in an existing oxidation pond for sediment remediation, algae growth, carbon conversion and power generation, simultaneously.

scholarly journals The Collimated Propagation Causes of Astrophysical and Laboratory Jets

2021 ◽  
Vol 65 (6) ◽  
pp. 477-487
Author(s):  
I. Yu. Kalashnikov ◽  
A. V. Dodin ◽  
I. V. Il’ichev ◽  
V. I. Krauz ◽  
V. M. Chechetkin
Keyword(s):  
Laboratory Experiments ◽  
Scaling Laws ◽  
Drift Chamber ◽  
Young Stars ◽  
Point Of View ◽  
Kurchatov Institute ◽  
Environmental Resistance ◽  
Scaling Parameters ◽  
Study Laboratory ◽  
Z Pinch

Abstract The use of Z-pinch facilities makes it possible to carry out well-controlled and diagnosable laboratory experiments to study laboratory jets with scaling parameters close to those of the jets from young stars. This makes it possible to observe processes that are inaccessible to astronomical observations. Such experiments are carried out at the PF-3 facility (“plasma focus,” Kurchatov Institute), in which the emitted plasma emission propagates along the drift chamber through the environment at a distance of one meter. The paper presents the results of experiments with helium, in which a successive release of two ejections was observed. An analysis of these results suggests that after the passage of the first supersonic ejection, a region with a low concentration is formed behind it, the so-called vacuum trace, due to which the subsequent ejection practically does not experience environmental resistance and propagates being collimated. The numerical modeling of the propagation of two ejections presented in the paper confirms this point of view. Using scaling laws and appropriate numerical simulations of astrophysical ejections, it is shown that this effect can also be significant for the jets of young stars.

Sediment Resuspension and Transport by Internal Solitary Waves

2019 ◽  
Vol 51 (1) ◽  
pp. 129-154 ◽  
Author(s):  
Leon Boegman ◽  
Marek Stastna
Keyword(s):  
Internal Waves ◽  
Laboratory Experiments ◽  
Sediment Resuspension ◽  
Vital Role ◽  
Continental Margins ◽  
Scale Models ◽  
Key Driver ◽  
Induced Currents ◽  
Wave Induced ◽  
Oriented Research

Large-amplitude internal waves induce currents and turbulence in the bottom boundary layer (BBL) and are thus a key driver of sediment movement on the continental margins. Observations of internal wave–induced sediment resuspension and transport cover significant portions of the world's oceans. Research on BBL instabilities, induced by internal waves, has identified several mechanisms by which the BBL is energized and sediment may be resuspended. Due to the complexity of the induced currents, process-oriented research using theory, direct numerical simulations, and laboratory experiments has played a vital role. However, experiments and simulations have inherent limitations as analogs for oceanic conditions due to disparities in Reynolds number and grid resolution, respectively. Parameterizations are needed for modeling resuspension from observed data and in larger-scale models, with the efficacy of parameterizations based on the quadratic stress largely determining the accuracy of present field-scale efforts.

Effects of narrowed social distance on local and international celebrity-endorsed advertisement attitudes

2020 ◽  
Vol 37 (5) ◽  
pp. 521-532
Author(s):  
Dave Centeno ◽  
Jeff Jianfeng Wang
Keyword(s):  
Social Distance ◽  
Design Methodology ◽  
Laboratory Experiments ◽  
Consumer Attitudes ◽  
Social Categories ◽  
Celebrity Endorsements ◽  
Content Type ◽  
Relational Approach ◽  
Close Relationship ◽  
Celebrity Endorsers

Purpose This paper aims to examine the effects of narrowing social distance with celebrity endorsers (i.e. via close relationship social categories) and their origin (i.e. local or international) on consumer attitudes about advertisements. It is proposed that using such a relational approach to celebrity endorsement, where celebrities are framed as socially close social categories, leads to more favorable attitudes toward the advertisement. Design/methodology/approach A pilot test on actual advertisements and three laboratory experiments tested the proposed hypotheses on the effects of varying celebrity social distance levels, with self-referencing as mediator, on attitudes toward the advertisements. Findings Celebrity endorsements are more effective when the advertisement features celebrities as socially close social category; furthermore, these effects are more pronounced when the celebrity is local as opposed to foreign. The study also proposes that consumer self-referencing vis-a-vis celebrities’ social distance through framed social categories mediates these effects. Originality/value Anchored in the identity and social identity theories, implications on relational approaches to celebrity endorsements and international marketing communications are discussed together with the fact that Asian culture inherently subscribes to relational celebrity endorsements.

Response of diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT) trace metal profiles in sediments to phytodetritus mineralisation

2012 ◽  
Vol 9 (1) ◽  
pp. 41 ◽  
Author(s):  
Yue Gao ◽  
Martine Leermakers ◽  
Annelies Pede ◽  
Aurelie Magnier ◽  
Koen Sabbe ◽  
...  
Keyword(s):  
Thin Films ◽  
Trace Metals ◽  
Trace Metal ◽  
Phytoplankton Bloom ◽  
Marine Ecosystem ◽  
Trace Metal Concentration ◽  
Water Interface ◽  
Overlying Water ◽  
Study Laboratory ◽  
Diffusive Gradients

Environmental contextContaminated sediments can have a large and lasting effect on marine ecosystems. It was discovered that significant amounts of pollutants, especially arsenic, were released from contaminated sediments during a phytoplankton bloom in the Belgian Continental Zone. Once released to the water column, these pollutants can accumulate up marine food chains and be a source of contaminants to humans. AbstractField data from the Belgian Continental Zone showed elevated trace metal concentrations at the sediment–water interface after the occurrence of a phytoplankton bloom. In the present study, laboratory incubation experiments were used to investigate the effect of the phytodetritus remineralisation process on the release of trace metals from contaminated muddy sediments. This remineralisation process was followed by the measurement of chlorophyll-a and dissolved organic carbon levels in the top sediment layers. Two gel techniques, diffusive equilibrium in thin films (DET) and diffusive gradients in thin films (DGT), were used to assess vertical metal profiles in the sediment pore waters and to calculate the metal effluxes. These metal effluxes compared very well with the trace metal concentration variations in the overlying water of the sediment. Much higher effluxes of Mn, Co and As were observed after 2 days of incubation in the microcosms which received additions of phytodetritus. This trend gradually decreased after 7 days of incubation, suggesting that the elevated efflux of trace metals was proportional to the quantity of phytodetritus mineralised at the sediment–water interface. The release of large amounts of toxic elements from the sediments after phytoplankton blooms can therefore potentially affect the marine ecosystem in the Belgian Continental Zone.

Experimental and Numerical Investigations of the 3-D Turbulent Flow Characteristics Around Submerged Permeable Breakwaters

2017 ◽  
Author(s):  
Caleb Stanley ◽  
Georgios Etsias ◽  
Steven Dabelow ◽  
Dimitrios Dermisis ◽  
Ning Zhang
Keyword(s):  
Turbulent Flow ◽  
Laboratory Experiments ◽  
Flow Characteristics ◽  
Mean Flow ◽  
Turbulent Structures ◽  
3 Dimensional ◽  
The Mean ◽  
Design Simplicity ◽  
Study Laboratory ◽  
Geometric Designs

Submerged breakwaters are favored for their design simplicity in projects intended to dissipate wave energy and reduce erosion on coastlines. Despite their popularity, the effects that submerged breakwaters exhibit on the surrounding hydrodynamics are not clearly understood, mainly due to the flow complexity generated from 3-dimensional turbulent structures in the vicinity of the breakwaters that affect the mean flow characteristics and the transport of sediment. The objective of this study was to evaluate the effects that various geometric designs of submerged permeable breakwaters have on the turbulent flow characteristics. To meet the objective of this study, laboratory experiments were performed in a water-recirculating flume, in which the 3-dimensional velocity field was recorded in the vicinity of scaled breakwater models. Breakwaters that were tested include non-permeable, three-hole, and ten-hole models. The experimental data obtained was compared to results obtained from numerical simulations. Results demonstrated that permeable breakwaters exhibit more vertical turbulent strength than their non-permeable counterparts. It was also discovered that three-hole breakwater models produce higher turbulent fluctuations than that of the ten-hole breakwaters. The results from this study will be used eventually to enhance the performance of restoration projects in coastal areas in Louisiana.

Study on Phosphorus Distribution from Sediment of Different Trophic Area of Taihu Lake and its Temporal Changes

2013 ◽  
Vol 295-298 ◽  
pp. 1663-1666
Author(s):  
Jian Hang Qu ◽  
Xiao Bing He ◽  
Hai Feng Li ◽  
Huan Chen Zhai ◽  
Yuan Sen Hu
Keyword(s):  
Taihu Lake ◽  
Algal Growth ◽  
Eutrophic Lake ◽  
Temporal Changes ◽  
Phosphorus Concentration ◽  
Lower Grade ◽  
Lake Area ◽  
Overlying Water ◽  
Phosphorus Forms ◽  
Water Eutrophication

Phosphorus is the key restraining factor for algal growth and water eutrophication, which is a global problem of environmental pollution. Using a sequential phosphorus extraction method, the phosphorus forms in sediment and their distribution from different trophic area of Taihu Lake (China) and their temporal changes were studied. Results showed that, concentration of Fe-P in sediment was the highest and successively Al-P, which was much higher than that of Ca2-P, Ca10-P, Ca8-P and O-P. All the phosphorus forms were more abundant in sediment 16# of eutrophic lake area, higher than that of moderate eutrophic and the lower-grade trophic area, with the last as relatively the lowest. Phosphorus concentration in June and September was much higher than that of March. Phosphorus in sediment of Taihu Lake had great releasing potential to the overlying water.

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