scholarly journals Role of Suspended Sediments and Mixing in Reducing Photoinhibition in the Bloom-Forming Cyanobacterium Microcystis

2012 ◽  
Vol 04 (12) ◽  
pp. 1029-1041 ◽  
Author(s):  
Justin D. Chaffin ◽  
Thomas B. Bridgeman ◽  
Scott A. Heckathorn ◽  
Ann E. Krause
Keyword(s):  
Suspended Sediments

The Role of Suspended Sediments in the Nutrition of Zooplankton in Turbid Reservoirs

Ecology ◽  
1983 ◽  
Vol 64 (5) ◽  
pp. 1225-1235 ◽  
Author(s):  
Joseph A. Arruda ◽  
G. Richard Marzolf ◽  
Robin T. Faulk
Keyword(s):  
Suspended Sediments

Distributed modeling of radionuclide washing out from the watersheds in solute and with suspended sediments: case studies Abukuma River, Fukushima Prefecture and Pripyat – Dnieper river system, Ukraine

2020 ◽  
Author(s):  
Mark Zheleznyak ◽  
Oleksandr Pylypenko ◽  
Sergii Kivva ◽  
Kazuyuki Sakuma ◽  
Yasunori Igarashi ◽  
...  
Keyword(s):  
Transport Model ◽  
Suspended Sediments ◽  
Transport Processes ◽  
Computational Time ◽  
Type Model ◽  
Distributed Data ◽  
Radionuclide Transport ◽  
Fukushima Prefecture ◽  
Distributed Models

<p>The measurements of  <sup>137</sup>Cs concentration in the rivers of Fukushima prefecture demonstrate the more significant role of the fluxes of <sup>137</sup>Cs adherent to the suspended sediments in comparison with the rivers contaminated after the Chernobyl accident. Therefore the forecasting of   <sup>137</sup>Cs  concentration during the floods requires to use the models of radionuclide wash-off from the watersheds with sediments.</p><p>Comprehensive modeling of radionuclide transport processes could be provided on the basis of the physically-based distributed models of hydrological and sediments transport processes. Such distributed models can describe soil erosion and sedimentation processes, as also exchange of the radionuclides between solute, suspended sediment and upper soil level.  We developed such type .model DSHVM-R based on the distributed hydrological- sediment transport model DHSVM of Washington University.  The model implementation for the experimental plots in Fukushima prefecture demonstrated a good possibility of the model for the analyses on the influence of the steepness of the watershed slopes and the intensity of the rainfall in the increased role of particulate <sup>137</sup>Cs transport.  From another side,  the implementation of such a model for large river watershed required too large computational time and significant efforts for processing of the large sets of the distributed data still not available for all watersheds.</p><p>We developed model RETRACE _RS  that combines the simplicity of the watershed empirical models based on the washing -out coefficient approach with the possibility to use geographically distributed data of the radioactive fallout and  GIS layers for rivernets. The model RETRACE_RS is an extension of the model RETRACE _R  (Zheleznyak et al, 2010),  which code is integrated into the Hydrological Dispersion  Module of the Decision Support System RODOS.   RETRACE_R is based on the assumptions that the rate of the radionuclide wash- off from each elementary grid cell of the watershed can be calculated from precipitation rate and density of deposition in this cell through the “wash-off” coefficient Kw; and that the radionuclides washed out from the cell are transported without time delay to the nearest river channel cell - to the grid element of the 1-D river model RIVTOX as lateral inflow. In RETRACE _RS the possibility of RETRACE_R to simulate washing -out of the radionuclides from watershed to river in solute was extended by the fluxes of the particulate radionuclide transport calculated via the “ washing out coefficient for particulate radionuclide transport ” -Kss. The formula to calculate Kss values is based on the empirical relations for the particulate  <sup>137</sup>Cs transport in the rivers of Fukushima prefecture ( Sakuma et al, 2019). The model was tested on the basis of the measurements of <sup>137</sup>Cs concentration in Abukuma river during the high floods in 2018-2019. The modeling system RETRACE_RS  - RIVTOX was validated also on the basis of the data sets of radionuclide transport in the Pripyat and Dnieper rivers. The system is testing for the prediction of aquatic radionuclide transport from the Chernobyl NPP area to the  Kyiv region during the extreme floods.</p><p> </p>

Role of suspended sediments on the distribution of PCB in the Seine Estuary (France)

1987 ◽  
Vol 7 (11-12) ◽  
pp. 1345-1350 ◽  
Author(s):  
Alain Abarnou ◽  
Jacques Avoine ◽  
Jean Paul Dupont ◽  
Robert Lafite ◽  
Serge Simon
Keyword(s):  
Suspended Sediments ◽  
Seine Estuary

scholarly journals SEDIMENT TRANSPORT DUE TO CURRENT-SUPPORTED TURBIDITY CURRENTS OVER AN ERODIBLE BED

2018 ◽  
pp. 33
Author(s):  
Celalettin Emre Ozdemir ◽  
Sahar Haddadian
Keyword(s):  
Boundary Layer ◽  
Settling Velocity ◽  
Critical Shear Stress ◽  
Suspended Sediments ◽  
Turbidity Currents ◽  
Gravitational Acceleration ◽  
Boundary Layer Turbulence ◽  
Erosion Coefficient ◽  
Self Motion

Wave- and current-supported turbidity currents (WCSTCs), are one of the chief participants in shaping the marine geomorphology. What makes WCSTCs different from other turbidity currents is that boundary layer turbulence is required to suspend the sediments rather than the self-motion of the turbidity currents. In the presence of a mild slope, the gravitational acceleration drives the suspended sediments offshore (Sternberg et al., 1996; Wright et al., 2001). Depending on what dominates the boundary layer turbulence (BLT), we further define two major subclasses of WCSTCs: (i) wave-supported (WSTCs), and (ii) current-supported turbidity currents (CSTCs). Although significant advances have been made on the details of WSTCs (Ozdemir et al., 2011; Yu et al., 2014; Cheng et al., 2015), less is known about CSTCs. The objective of present study is to investigate the role of alongshore currents on CSTC dynamics over an erodible bottom boundary. The focus here is to identify the possible role of erosion on CSTC dynamics, and assess the coupling between current-induced BLT and suspended sediments for various bed erodibility parameters, i.e. critical shear stress, erosion coefficient, and settling velocity.

scholarly journals Assessing the impacts of the main river and anthropogenic use on the degree of metal contamination of oxbow lake sediments (Tisza River Valley, Hungary)

2019 ◽  
Vol 20 (3) ◽  
pp. 1662-1675 ◽  
Author(s):  
Izabella Babcsányi ◽  
Margit Tamás ◽  
József Szatmári ◽  
Beáta Hambek-Oláh ◽  
Andrea Farsang
Keyword(s):  
Suspended Sediments ◽  
Pollution Load Index ◽  
Anthropogenic Sources ◽  
Oxbow Lake ◽  
Oxbow Lakes ◽  
Pollution Load ◽  
Metal Concentrations ◽  
Main River ◽  
Tisza River

Abstract Purpose Oxbow lakes, reaches that were cut off from a river during river straightening works, can accumulate during flooding metal-rich suspended sediments transported by a river from mining-impacted source areas and other anthropogenic sources. Additionally, the anthropogenic use of oxbow lakes may significantly impact the sediment-bound metal concentrations. The aim was to determine the dominating effect in the sediments’ enrichment in heavy metals. Materials and methods We collected surface sediments (< 10-cm depth) from seven oxbow lakes once connected to the Tisza River (a transboundary river in Central and Eastern Europe). Four of the oxbows were located on the active floodplain, while three oxbows were at the reclaimed side (i.e., outside the flood defense levee). The sediment samples were subjected to total metal analyses (Cd, Co, Cr, Cu, Ni, Pb, and Zn) and sequential chemical extractions. Results and discussion Contamination indices (geoaccumulation index (Igeo) and pollution load index (PLI)) show a moderate but significant metal pollution of oxbow lakes situated on the active floodplain (Igeo (Pb) 0.95–1.25, PLI 2.1–2.8) and an overall unpolluted to slightly polluted status of those at the reclaimed side (Igeo (Pb) − 0.36–0.51, PLI 1.3–1.7). Additionally, the geochemical fractionation of the target metals showed that Cd and Zn were the most labile (Cd 29–48%, Zn 18–37% of non-residual proportions), indicating their environmental significance. Conclusions Canonical discriminant analysis of the sediment-bound metal concentrations revealed the prevalent role of the river connection over the anthropogenic use in controlling the metal enrichment of oxbow sediments.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor
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