This thesis describes methodologies to detemiine organic and inorganic phosphorus in
water and discusses biological, physical and chemical controls on the transformations of
organic and inorganic phosphorus in laboratory microcosms of estuarine particle-water
systems. Phosphorus is an important nutrient and the accurate determination of
phosphorus species in natural waters is essential for understanding the biogeochemical
cycling of the element. Chapter one reviews phosphorus impacts on water quality and
relevant UK legislation, the sources, speclation and fractionation of phosphorus, the
sediment/water phosphorus cycle and analytical methods for the determination of
dissolved Inorganic phosphorus (DIP) and organic phosphorus (DOP) species In natural
waters.
Chapter two introduces the technique of segmented flow analysis and describes
methods for the determination of inorganic phosphorus and total dissolved phosphorus
after autoclaving. Segmented flow analysis is suitable for determining inorganic P and
organic P species in freshwaters in the range of 1 - 300 pg P L"\ Calibrations were linear
(R^ > 0.997) over the range 0.5 - 100 pg P L'^ with good precision (RSDs < 3 %). The
LCD was 0.4 pg P L'^ for DIP and 3 pg P L'^ for DOP. The recoveries of 7 model organic
phosphorus compounds (adenosine-5-triphosphate di-sodium salt (ATP), phytic acid
(PTA), sodium tripolyphosphate (STP), methyltriphenylphosphonium bromide (MPT),
p-nitrophenyl phosphate magnesium salt (p-NPP), p-D-glucose-6-phosphate
monosodium salt (G-6-P) and cocartjoxylase (COCA)) were all > 90 %.
Chapter three reports on bacterial uptake studies of phosphorus species in a plug-flow
microcosm. Experiments using inert Duran and Siran beads as supports for bacterial
bioflim development showed similar P uptake behaviour. Glucose-6-phosphate was
almost fully utilised and converted to DIP after 3 days suggesting that labile organic
phosphorus species could be a bioavailable source of P for bacteria. Phytic acid (a
refractory P compound) released significant concentrations of DIP to the water column
due to physical displacement.
Chapter four describes phosphonjs transformations in a sediment-water flume due to
turbulent resuspension events. The released DIP concentration had a strong linear
relationship with shear stress in pure water and artiflcial seawater. However, no
signtflcant relationship between DOP release and shear stress was observed. The
sediment type and the water matrix significantly affected the magnitude of DIP and DOP
release to the water column.
Chapter flve extends the investigation of P exchange to constant resuspension events.
The water matrix had a significant effect on the rate of DIP and DOP release from
sediment and the sedimentAvaler equilibration time. Typically 6 - 12 % of total
phosphorus in the sediment was released as DIP and DOP into the water column. When
orthophosphate and phytic acid were added to both UHP and river water. SPM was able
to buiffer theses additions. However, the SPM buffering capacity was much lower for
G-6-P. The buffering capacity of the SPM for phytic acid was significant and permanent
in UHP and biotic river water, whereas phytic acid was cycled in the abiotic experiments.
Date of Award | 2009 |
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Original language | English |
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Awarding Institution | |
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TRANSFORMATIONS OF ORGANIC AND INORGANIC PHOSPHORUS IN ESTUARINE PARTICLE- WATER SYSTEMS
Zhao, J. B. (Author). 2009
Student thesis: PhD