Suspended Sediments
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Author(s):  
D. A. Antonenkov ◽  
◽  
A. E. Shchodro ◽  

The article presents the methodology of hydrological modeling of water flows for constructing flow plans in the design of hydraulic structures. On the basis of these calculations, both the specific costs of bottom and suspended sediments in each flow stream and the deformation of the riverbed at various points in time can be determined. The results of experiments with spatial models of river sections are considered. The developed technique makes it possible to calculate the deformation of the bottom and shores and form a flow organization scheme, which, due to an increase in velocities in some section of the channel, ensures sediment transport to more remote areas of the seashore, up to the open sea.


Author(s):  
Eisa Ebrahimi ◽  
Hossein Asadi ◽  
Mehrnosh Joudi ◽  
Mehran Rezaei Rashti ◽  
Mohammad Bagher Farhangi ◽  
...  

Abstract Phosphorus (P), nitrogen (N) and organic component are released from the soil into surface bodies by runoff and erosion, causing the pollution and eutrophication of water resources. This study was aimed to investigate the seasonal changes in loads of N and P components, and organic matter (OM) in the Pasikhan River in flood and normal conditions. Sampling was performed monthly during normal flow conditions and for five flood events. The concentrations of P and N components were measured in the samples. The OM of the suspended sediments was determined by the combustion method. Under the normal flows, the maximum loads of total P and OM were about 0.553 mg l−1 (STD = 0.11) (November) and 3.41% (STD = 1.17) (November) in the autumn, respectively. The total N concentration of 0.533 mg l−1 (STD = 0.12) was observed in the winter. In the flood events, the TP, TN and OM ranged from 0.48 to 3.5 mg l−1, 0.28 to 0.79 mg l−1 and 1.24 to 4.11%, respectively. The results indicated a high risk of eutrophication in the Pasikhan River. Also, the study revealed that in a severe flood event, some 113.9 tons h−1 of OM can be released from the river watershed. Furthermore, there was a high correlation between the amount of P and OM losses with the concentration of suspended sediments in different flood events. Finally, it is concluded that if the floods are not controlled, they not only cause a rapid loss of soil nutrients and OM but also lead to severe eutrophication in the Anzali wetland.


2021 ◽  
Author(s):  
Ben Kefford ◽  
Susan J. Nichols ◽  
Richard Duncan

Biodiversity is declining, typically because of multiple anthropogenic stressors. Cumulative effects of multiple stressors are classified as additive, when cumulative effects are as expected from the stressor’s singular effects, synergistic when greater than additive or antagonistic when less than additive. Less attention has been given to the consistency of cumulative effects. We analysed stream insects, Ephemeroptera, Plecoptera and Trichoptera (EPT) data from two habitats spanning a 3,600 km latitudinal (S11◦-S43◦) gradient in eastern Australia. We found that the cumulative effect of salinity and suspended sediments on EPT family richness was inconsistent with additive, synergistic or antagonistic effects, and the reduction EPT family richness from increasing both stressors varied (48-70%) depending on habitat (riffle vs. edge), water temperature and terrain slope. Studies of cumulative effects of multiple stressors at one location risk not describing cumulative effects elsewhere and ecologists should consider the spatial consistency of multiple stressors.


2021 ◽  
Author(s):  
◽  
Taputukura Raea

<p>Land based-effects, including sedimentation are threatening estuarine and coastal systems globally. Ecological systems are faced with significant pressures from human activities including toxic pollution, eutrophication, habitat fragmentation and sedimentation. In recent years sediment inputs into marine systems have been greatly accelerated through land-based activities such as urban-land use, agriculture, coastal developments, large scale land clearances and farming. Effects of sedimentation on marine organisms include suffocation, reduced foraging efficiency and clogging of the gills of filter feeders.  In New Zealand, sedimentation is the most important land-based stressor on the coastal marine environment. The pāua (Haliotis iris), is an important macroalgal grazer and is one of New Zealand’s top 10 seafood exports. However, little is known about the effects suspended sediments have on H. iris. The aim of this thesis is to experimentally test the effects of suspended sediment on the growth, oxygen consumption and mucus production for H. iris, using sediment concentrations that would naturally occur within Wellington Harbour, New Zealand.  Suspended sediment had no significant effect on H. iris growth or oxygen consumption. However, exposure to suspended sediments significantly reduced mucus production in H. iris. There were also trends in the data to suggest that respiration in smaller H. iris was reduced by suspended sediments.  Limited studies have explored the effect of suspended sediments on gastropods, even though sedimentation is one of the most significant land based stressors on the marine environment, not only in New Zealand, but also worldwide. This study has led to a better understanding of the potential implications suspended sediment may incur for not only H. iris, but also Haliotis species in general.</p>


2021 ◽  
Author(s):  
◽  
Taputukura Raea

<p>Land based-effects, including sedimentation are threatening estuarine and coastal systems globally. Ecological systems are faced with significant pressures from human activities including toxic pollution, eutrophication, habitat fragmentation and sedimentation. In recent years sediment inputs into marine systems have been greatly accelerated through land-based activities such as urban-land use, agriculture, coastal developments, large scale land clearances and farming. Effects of sedimentation on marine organisms include suffocation, reduced foraging efficiency and clogging of the gills of filter feeders.  In New Zealand, sedimentation is the most important land-based stressor on the coastal marine environment. The pāua (Haliotis iris), is an important macroalgal grazer and is one of New Zealand’s top 10 seafood exports. However, little is known about the effects suspended sediments have on H. iris. The aim of this thesis is to experimentally test the effects of suspended sediment on the growth, oxygen consumption and mucus production for H. iris, using sediment concentrations that would naturally occur within Wellington Harbour, New Zealand.  Suspended sediment had no significant effect on H. iris growth or oxygen consumption. However, exposure to suspended sediments significantly reduced mucus production in H. iris. There were also trends in the data to suggest that respiration in smaller H. iris was reduced by suspended sediments.  Limited studies have explored the effect of suspended sediments on gastropods, even though sedimentation is one of the most significant land based stressors on the marine environment, not only in New Zealand, but also worldwide. This study has led to a better understanding of the potential implications suspended sediment may incur for not only H. iris, but also Haliotis species in general.</p>


2021 ◽  
Author(s):  
Leonardo Mena-Rivera ◽  
Charlotte E.M. Lloyd ◽  
Michaela K. Reay ◽  
Tim Goodall ◽  
Daniel S Read ◽  
...  

Abstract The dynamic interactions between dissolved organic matter (DOM) and particulate organic matter (POM) are central in nutrient cycling in freshwater ecosystems. However, the molecular-level mechanisms of such interactions are still poorly defined. Here, we study spatial differences in the chemical and molecular composition of suspended sediments in the River Chew, UK. We then applied a compound-specific stable isotope probing (SIP) approach to test the potential assimilation of 13C,15N-glutamate (Glu) and 15N-nitrate into proteinaceous biomass by particle-associated microbial communities over a 72-h period. Our results demonstrate that the composition of suspended sediments is strongly influenced by the effluent of sewage treatment works (STW). Fluxes and percentages of assimilation of both isotopically labelled substrates into individual proteinaceous amino acids (AAs) showed contrasting dynamics in processing at each site linked to primary biosynthetic metabolic pathways. Preferential assimilation of the organic molecule glutamate and evidence of its direct assimilation into newly synthesised biomass was obtained. Our approach provides quantitative molecular information on the mechanisms by which low molecular weight DOM is mineralised in the water column compared to an inorganic substrate. This is paramount for better understanding the processing and fate of organic matter in aquatic ecosystems.


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