A l-D tidally resolving hydrodynamic model of the Tweed Estuary has been encoded
using the Estuarine Contaminant Simulator, ECoS. The model results of axial and time
series variations in water elevation, salinity and turbidity are compared to field data
recorded during the LOIS survey programme.
The organic and inorganic controls on estuarine pH have also been investigated by
encoding a new template to predict the effect of changing salinity and temperature on the
pH of estuarine water. The template has been coupled to the hydrodynamic model to
predict pH variations in the estuary. The model results have shown conservative behaviour
of the inorganic carbon system through out the majority of the estuary, but also identified
an area of potentially high photosynthetic activity near the limit of saline intrusion during
periods of low summer flows. Low (< 2 ^g 1"') concentrations of chlorophyll a in the water
column and increases in pH correlated with tidal inundation of the river estuary banks
imply that benthic photosynthetic process are important water chemistry in the upper
estuary.
The effects of salinity, turbidity and pH on Kd(Cd) and K<i(Zn) has been investigated using
radiotracer incubation experiments and analytically determined measurements. The results
show a reduction in IQ with increased salinity, but that the K<iS determined analytically are
an order of magnitude higher than those measured when radiotracers are used. Analytically
determined K<iS are reduced with increasing SPM concentration and increased at higher
pH. Although no photosynthetically mediated control of radiotracer uptake was identified
partitioning was significantly reduced (> 90 %) when a metabolic inhibitor was added.
The Kd has been encoded as an exchange transfer and used to predict axial distributions
and the flux of these metals from the riverine catchment to the sea. Model results indicate
that the partition coefficients determined fi-om the radiotracer studies can not fully account
for the analytically determined distribution between phases. It is hypothesised that colloids
and Fe-Mn oxides precipitates play a significant role in trace metal transpon in low
turbidity, high pH conditions. The results have implications for the measurement and
modelling of chemical fluxes in low turbidity systems.
Date of Award | 2000 |
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Original language | English |
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Awarding Institution | |
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MEASUREMENT AND MODELLING OF ESTUARINE CHEMISTRY
PUNT, A. G. (Author). 2000
Student thesis: PhD