scholarly journals 1-D Vertical Flux Dynamics in a Low-Gradient Stream: An Assessment of Stage as a Control of Vertical Hyporheic Exchange

Water ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 708 ◽  
Author(s):  
F. Claire Harris ◽  
Eric W. Peterson
Keyword(s):  
Vertical Flux ◽  
Hyporheic Exchange ◽  
Exchange Relationships ◽  
Flux Dynamics ◽  
Near Surface ◽  
Advection Dispersion ◽  
Average Flux ◽  
Multi Level ◽  
Approach Zero ◽  
Variable Flux

This study characterized vertical one-dimensional (1-D) flux rates in the top 150 cm of the streambed and explored the relationship between stage and 1-D vertical flux rates in a low-gradient stream. Six multi-level samplers were installed along a 25 m stretch of the thalweg spaced at 5 m intervals. Each sampler recorded temperature at five separate depths (30, 60, 90, and 150 cm) from February 2009 to March 2010. Temperature and stage data were collected at 15 min intervals. For the midpoint between sensors, 1-D flux rates were calculated using the 1-D conduction-advection-dispersion equation utilized in the VFLUX MATLAB program. The dominant flux direction at a depth of 15 cm was downward (negative), while the average flux directions at depths of 45, 75, and 120 cm were upward (positive). Variable flux directions above 15 cm indicated hyporheic exchange with background upwelling groundwater between 15 to 120 cm. Flux rates approach zero in the summer, representing limited hyporheic exchange. Relationships between stage and flux at the near-surface streambed (15 cm) were weak, but statistically significant, with Spearman’s rank correlations for all six multi-level samplers ranging from −0.032 to 0.369 with an average of 0.085.

Dissipation in the Bay of Bengal from a Seaglider

2021 ◽  
Author(s):  
Gillian Damerell ◽  
Peter Sheehan ◽  
Rob Hall ◽  
Adrian Matthews ◽  
Karen Heywood
Keyword(s):  
Time Series ◽  
Bay Of Bengal ◽  
Gradual Decrease ◽  
Vertical Flux ◽  
Sensor System ◽  
Atmospheric Forcing ◽  
Near Surface ◽  
Average Profile ◽  
Time Average

<p>In July 2016, a Seaglider equipped with a microstructure sensor system was deployed in the southern Bay of Bengal at 7° 54.0′ N, 89° 4.5′ E.  162 profiles (of which 146 were to 1000 m) of microstructure shear and temperature were collected as a time series at the same location.  Dissipation is calculated independently from both shear and temperature.  The time-average profile shows high dissipation (nearly 1×10<sup>-5</sup> W kg<sup>-1</sup>) near the surface, dropping rapidly over the uppermost 50 m to ~1×10<sup>-7</sup> W kg<sup>-1</sup>, followed by a more gradual decrease to ~5×10<sup>-10</sup> W kg<sup>-1</sup> at 300m.  A band of slightly higher dissipation around 500 m (~8×10<sup>-10</sup> W kg<sup>-1</sup>) could facilitate an increased vertical flux of nutrients, heat, salinity, etc at these depths.  From 600 to 1000 m dissipation remains roughly constant at ~1×10<sup>-10</sup> W kg<sup>-1</sup>.  Variability of the near surface dissipation in response to atmospheric forcing is also discussed.</p>

Near-Surface Vertical Flux Divergence in the Stable Boundary Layer

2018 ◽  
Vol 169 (3) ◽  
pp. 373-393 ◽  
Author(s):  
L. Mahrt ◽  
Christoph K. Thomas ◽  
Andrey A. Grachev ◽  
P. Ola G. Persson
Keyword(s):  
Boundary Layer ◽  
Stable Boundary Layer ◽  
Vertical Flux ◽  
Flux Divergence ◽  
Near Surface ◽  
Stable Boundary

scholarly journals A multi-level analysis of team climate and interpersonal exchange relationships at work

2008 ◽  
Vol 19 (2) ◽  
pp. 195-211 ◽  
Author(s):  
Herman H.M. Tse ◽  
Marie T. Dasborough ◽  
Neal M. Ashkanasy
Keyword(s):  
Team Climate ◽  
Exchange Relationships ◽  
Multi Level ◽  
Level Analysis

Evaluation of Retardation Effect of Cesium Ions Through Groundwater Unsaturated Zone

2016 ◽  
Author(s):  
Takenori Ozutsumi ◽  
Yuichi Niibori ◽  
Taiji Chida
Keyword(s):  
Unsaturated Zone ◽  
Nuclear Power ◽  
Experimental Results ◽  
Retardation Effect ◽  
Silica Sand ◽  
Flow Paths ◽  
Near Surface ◽  
Advection Dispersion ◽  
Unsaturated Condition ◽  
Eastern Japan

Around near-surface underground, an unsaturated zone is formed in such porous layer composed of mainly silicate and silica sand. In the unsaturated zone in which pores are not completely filled with groundwater but also air, the migration of RNs is influenced by the presence of air phase. So far, though many studies have been reported about the unsaturated zone, little studies on the relation of the unsaturated zone and the migration of RNs have been carried out. In this study, the change of the migration of tracer ions in the unsaturated zone was examined by using a bed column, and analyzed by applying advection dispersion equation to the experimental results. As tracer ions, cesium (Cs) and strontium (Sr) were chosen in this study. These elements are the most important elements for the decontamination of Eastern Japan area caused by Fukushima the Daiichi Nuclear Power Plant accident. The experimental results showed the facilitation of the migration of tracer ions in the unsaturated zone. This causes the decrease in the sorption of tracer ions due to the inhibition of air phase. That is, the increase in the retardation effect by the clogging with air phase in flow paths was not remarkable. In the assessment of RNs migration under the unsaturated condition, these competing effects should be reflected adequately.

Pinning and near-surface flux dynamics of the YBaCuO single crystal

1994 ◽  
Vol 235-240 ◽  
pp. 3225-3226
Author(s):  
L.G. Mamsurova ◽  
K.S. Pigalskiy ◽  
V.P. Sakun ◽  
L.G. Scherbakova
Keyword(s):  
Single Crystal ◽  
Surface Flux ◽  
Flux Dynamics ◽  
Near Surface

A Preliminary Study on the Transport Behavior for a Potential Disposal Site of LILW in Southern China

2011 ◽  
Vol 356-360 ◽  
pp. 1445-1453 ◽  
Author(s):  
Shu Ping Yi ◽  
Hai Yi Ma ◽  
Hua An Wang
Keyword(s):  
Southern China ◽  
Water Pressure ◽  
Site Investigation ◽  
Disposal Site ◽  
Longitudinal Dispersion Coefficient ◽  
Near Surface ◽  
Transport Behavior ◽  
Advection Dispersion ◽  
Intermediate Level Radioactive Waste

Near surface disposal of low and intermediate level radioactive waste (LILW) requires a detailed site investigation of the potential sites, in which the transport behavior of solutes in the groundwater system is one of the key processes that needed to be addressed. An investigation is undertaking for the disposal of LILW at a potential site in Southern China. In-situ test have been conducted to study the hydrogeologic characteristics of the site. Firstly, tests including pit permeability tests, injecting tests, water pressure tests, pumping tests and laboratory permeability tests have been performed according to the specific field conditions. Hydraulic conductivities for different layers of rock and soils have been calculated and their recommended values have been presented. And then in-situ dispersion tests have been performed at an area adjacent to the disposal site with non-sorbed tracers. A numerical model has been developed for the site based on data obtained during the site investigation, and has been calibrated with available measured groundwater level and measured tracer concentrations in the dispersion tests. Calibrated results indicate that the longitudinal dispersion coefficient is equal to 5.0×10-3 m2/d. Preliminary predictions have been performed for the groundwater flow and solute advection-dispersion behavior according to the design of the site, in which the center valley will be backfilled with low permeable materials. Predicted results indicate that the groundwater exhibits a lower water table and a smaller hydraulic gradient under designed site condition than under natural condition. All the tracers remain underground in the site and transport slowly mainly through advection and dispersion. Finally, conclusions for the study have been presented and the key tasks for future work have been discussed. This study provides an insight understanding of the hydrogeology characteristics of the disposal site and is useful for the assessment of environment impacts of the site under disposal of LILW.

Benthic foraminiferal zonation in deep-water carbonate platform margin environments, northern Little Bahama Bank

1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin
Keyword(s):  
Deep Water ◽  
Benthic Foraminifera ◽  
Carbonate Platform ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Near Surface ◽  
Sediment Gravity Flows ◽  
Gravity Flows ◽  
Platform Margin ◽  
Water Carbonate

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.

Analysis of 2D and 3D defects associated with precipitation of Cu in silicon

1991 ◽  
Vol 49 ◽  
pp. 870-871
Author(s):  
P.M. Rice ◽  
MJ. Kim ◽  
R.W. Carpenter
Keyword(s):  
Colony Growth ◽  
Dark Field ◽  
Dark Side ◽  
Silicide Phase ◽  
Strain Fields ◽  
Near Surface ◽  
Unknown Composition ◽  
Secondary Precipitates ◽  
20 Nm ◽  
2D And 3D

Extrinsic gettering of Cu on near-surface dislocations in Si has been the topic of recent investigation. It was shown that the Cu precipitated hetergeneously on dislocations as Cu silicide along with voids, and also with a secondary planar precipitate of unknown composition. Here we report the results of investigations of the sense of the strain fields about the large (~100 nm) silicide precipitates, and further analysis of the small (~10-20 nm) planar precipitates.Numerous dark field images were analyzed in accordance with Ashby and Brown's criteria for determining the sense of the strain fields about precipitates. While the situation is complicated by the presence of dislocations and secondary precipitates, micrographs like those shown in Fig. 1(a) and 1(b) tend to show anomalously wide strain fields with the dark side on the side of negative g, indicating the strain fields about the silicide precipitates are vacancy in nature. This is in conflict with information reported on the η'' phase (the Cu silicide phase presumed to precipitate within the bulk) whose interstitial strain field is considered responsible for the interstitial Si atoms which cause the bounding dislocation to expand during star colony growth.

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