The development and field testing of a particle tracing technique for the prediction and
monitoring of cohesive sediment transport is described. Natural, chemical and water soluble
dye tracers have been used for many years to determine water circulation in order to predict
sediment transport. Radioactive and fluorescent particles have been used widely to predict
sediment particle transport, but have been restricted mainly to non-cohesive sand and gravel
transport studies due to the difficulties of preparation, handling, disassociation of the label
from the particle and labour-intensive analysis. The development of a fine cohesive tracing
technique therefore offered a significant advancement for the understanding and prediction
of fine cohesive sediment and pollutant dynamics in aquatic environments if a sediment
analogue could be developed.
The physical properties, including size, surface charge, fiuorescence and settling velocity of
natural fine cohesive sediment were analysed in order to passively and actively adsorb
organic fluorescent dyes onto the sediment surface; the tests were largely unsuccessful. The
physical properties of artificial fluorescent particles as sediment analogues were examined
and found to have a close correlation to natural sediment. Analysis of the fluorescent
particles in mud suspensions on an Analytical Flow Cytometer offered an automated and
accurate method of tracer concentration determination at low dilutions. A preliminary field
study was carried out in a small pool with encouraging results.
A study in a shallow freshwater lake was carried out to determine the sediment dynamics in
the lake. A depth-averaged model of the wind-driven circulation within the lake was used to
interpret the distribution of tracer. Secondary transport and deposition clearly led to an
accumulation of sediment and internal loading in the lake driven by hydrodynamical
forcing.
A study of the particle residence time and deposition-resuspension processes in the turbidity
maximum of a macro-tidal estuary. Fluorescent particles were released into the turbidity
maximum and were advected down-estuary on the ebb tide and up-esiuary on the flood tide.
The residual mass budgets indicated a significant deposition of the particles in the upper
estuary at slack high water. The particles were detected in estuarine surface waters 1 week
after release.
The fluorescent particles behaved in a similar way to the suspended sediment in both the
lacustrine and estuarine study and were considered as sutiable tracers for cohesive sediment.
Date of Award | 1995 |
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Original language | English |
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Awarding Institution | |
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DEVELOPMENT OF A TRACER TECHNIQUE FOR THE STUDY OF SUSPENDED SEDIMENT DYNAMICS IN AQUATIC ENVIRONMENTS
MARSH, J. K. (Author). 1995
Student thesis: PhD