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Modelling the Cohesive Sediment Transport in the Marine Environment: the Case of Thermaikos Gulf : Volume 3, Issue 1 (13/02/2007)

By Krestenitis, Y. N.

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Book Id: WPLBN0004020349
Format Type: PDF Article :
File Size: Pages 14
Reproduction Date: 2015

Title: Modelling the Cohesive Sediment Transport in the Marine Environment: the Case of Thermaikos Gulf : Volume 3, Issue 1 (13/02/2007)  
Author: Krestenitis, Y. N.
Volume: Vol. 3, Issue 1
Language: English
Subject: Science, Ocean, Science
Collections: Periodicals: Journal and Magazine Collection, Copernicus GmbH
Historic
Publication Date:
2007
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Kombiadou, K. D., Savvidis, Y. G., & Krestenitis, Y. N. (2007). Modelling the Cohesive Sediment Transport in the Marine Environment: the Case of Thermaikos Gulf : Volume 3, Issue 1 (13/02/2007). Retrieved from http://worldlibrary.net/


Description
Description: Laboratory of Maritime Engineering and Maritime Works, Division of Hydraulics and Environmental Engineering, Department of Civil Engineering, Aristotle University of Thessaloniki, 541 24, Thessaloniki, Greece. The transport of fine-grained sediments in the marine environment entails risks of pollutant intrusions from substances absorbed onto the cohesive flocks' surface, gradually released to the aquatic field. These substances include nutrients such as nitrate, phosphate and silicate compounds from drainage from fertilization of adjacent cultivated areas that enter the coastal areas through rivers and streams, or trace metals as remainders from urban and industrial activities. As a consequence, knowledge on the motion and distribution of sediment particles coming from a given pollutant source is expected to provide the 'bulk' information on pollutant distribution, necessary for determining the region of influence of the source and to estimate probable trophic levels of the seawater and potential environmental risks. In that aim a numerical model has been developed to predict the fate of the sediments introduced to the marine environment from different pollution sources, such as river outflows, erosion of the seabed, aeolian transported material and drainage systems.

The proposed three-dimensional mathematical model is based on the particle tracking method, according to which matter concentration is expressed by particles, each representing a particular amount of sedimentary mass, passively advected and dispersed by the currents. The processes affecting characteristics and propagation of sedimentary material in the marine environment, incorporated in the parameterization, apart from advection and dispersion, include cohesive sediment and near-bed processes. The movement of the particles along with variations in sedimentary characteristics and state, carried by each particle as personal information, are traced with time. Specifically, concerning transport processes, the local seawater velocity and the particle's settling control advection, whereas the random Brownian motion due to turbulence simulates turbulent diffusion. The vertical stratification of the water-column is taken into consideration by appropriate damping of the vertical diffusion term. Variations in cohesive sediment properties during the abidance in the aquatic environment include coagulation and flock break-up processes, quantification of the effects of ambient density to the density of the cohesive aggregate and the associated alterations to the falling speed of the particle. In the vicinity of the seabed, particles may deposit and gradually consolidate with time, the particles remain settled onto the bed, re-enter the flow at a later temporal point or may enter the water column for the first time, originating from the erosion of the bed. The occurrence of each of the aforementioned near-bed processes is defined according to the prevailing benthic shear stress conditions.

The mathematical model has been applied to the Thermaikos Gulf, an area of high environmental and socioeconomic importance but also a region of significant pollutant forcing from various anthropogenic activities taking place in the adjoining land. Various kinds of outputs can be extracted, such as trajectories of the overall movement of specific particles and related alterations of their characteristics with time, snapshots of the domain with respect to suspended or deposited matter and natural concentrations of sediments at every required temporal and spatial point. Indicative results from yearly and monthly simulations, using input baroclinic circulation data from the North Aegean Sea model and river discharges are presented and discussed, including outputs from a Typical One-Year Simulation (TOYS), the simulation of the period from 3 September 2001 to 31 August 2002 (S1A2) and the


Summary
Modelling the cohesive sediment transport in the marine environment: the case of Thermaikos Gulf

Excerpt
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