Sources, sinks and stores of Nitrogen and Phosphorus associated with public water supply and the vadose zone

Ascott, Matthew and Surridge, Ben and Gooddy, Daren (2019) Sources, sinks and stores of Nitrogen and Phosphorus associated with public water supply and the vadose zone. PhD thesis, Lancaster University.

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Abstract

Reactive Nitrogen (N) and Phosphorus (P) in the environment remain a considerable problem for both ecosystems and drinking water quality. Although public water supply processes and the vadose zone are well known components of the anthropogenically perturbed hydrological cycle, the impact of these components on N and P cycling is poorly understood. The aim of this thesis was to improve the understanding of sources, sinks and stores of N and P associated with public water supply and the vadose zone, to support the development of integrated nutrient management approaches. Mains water leakage is shown to be an important source of P, which will increase in importance in the future. Mains water leakage of P has significant temporal variability associated with winter burst events, summer shrink-swell leakage and active leakage control. Mains water leakage has also been shown to be an important source of N in urban areas, contributing up to 20% of all N loads. Abstraction for public water supply has been shown to be a considerable temporary sink of N, equivalent to up to 39% of denitrification. The unsaturated zone has also been shown to be an important store of nitrate, with the quantity of nitrate stored in the vadose zone being equivalent to 200% of estimates of inorganic N stored in soils globally. The results of this thesis have important implications for the development of integrated nutrient management approaches. The sources, sinks and stores associated with public water supply and the vadose zone quantified in this thesis should be considered in future macronutrient budgets and models. Continued use of existing models which do not consider these additional N and P sources, sinks and stores should be tempered with the knowledge gained from this research.