Molecular Level Speciation of Phosphorus in Suspended and Streambed Fluvial Sediments

Abstract

The impact of eutrophication, along with its associated consequences, is an environmental problem around the world. There have been numerous relevant studies and papers that have shown the significance of the correlation between the presence of phosphorus (P) in aquatic environments and the rate and intensity of eutrophication. Although the presence of P has largely been discussed in terms of its effects on the environment and water quality, most of the previous studies have not conducted a thorough molecular characterization of P species found in the suspended sediment contained in fluvial water systems. In this thesis, the importance of P speciation and a more thorough understanding of molecular analysis were discussed and reviewed. Moreover, the characterization methods of X-ray fluorescence (XRF), X-ray adsorption near edge structure (XANES) spectroscopy, and nuclear magnetic resonance 31P-NMR spectroscopy (P-NMR) were used to obtain comprehensive understanding of fluvial sediment samples in terms of their elemental, inorganic P, and organic P distributions, respectively. A significant seasonal influence on P speciation was observed, with an observed increase in the concentration of both organic P compounds and that of iron-associated P during the summer months. Moreover, the concentrations of both orthophosphate monoesters and diesters, including that of phytate and DNA, were also shown to increase consistently during the summer sampling periods compared to spring. Spatial differences were also observed, both in terms of site-to-site comparison as well as catchment inflow versus outflow, although the trends in data were relatively inconsistent when comparing the seasonal differences. The results from this research can be used for a variety of practical applications, such as improving the efficiency of eutrophication control, potential source tracing, and the further development of accurate modelling.