Development of Environmental Tracers for Sediments and Phosphorus.

Pryce, Owen (2011) Development of Environmental Tracers for Sediments and Phosphorus. PhD thesis, Lancaster University.

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Abstract

Tracing eroded sediments can aid in minimising the impacts of soil erosion by improving the understanding of transport processes. A large range of sediment tracers exists; however, to date there has been no combined use of tracers which represent the full particle size range of sediments transported in overland flow. This is relevant because particles of different sizes show differing transport behaviour, but are all capable of transporting sediment bound contaminants such as phosphorus. The aim of this project was to develop a dual tracing method for both sediments and colloids in order to better represent the transport of phosphorus. The link between soil erosion and eutrophication resulting from phosphorus transport was demonstrated. A range of sediment and colloid tracers were reviewed to select the two most appropriate tracers for this project (rare earth oxides (REOs) and fluorescent microspheres). Published methodologies relating to these tracers were investigated. The tracers were then applied to soil boxes receiving simulated rainfall, as well as a field plot, to compare their transport to the relevant phase of phosphorus. The results showed comparable behaviour between REOs and particulate phosphorus. Fluorescent microspheres had low recoveries in surface runoff due to infiltration into the soil profile which limited their ability to trace colloid bound phosphorus. However, REOs were shown to be a useful tracer due to their ability to identify the sources and transport pathways of particulate phosphorus. Furthermore, the results gained from methodological development are useful for the future development of both tracing methods. Therefore, the results of this thesis provide significant steps towards improved understanding of phosphorus transport from arable land which can lead to reductions in nutrient loss and eutrophication.