Nicholas Howden

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The development of complex agents requires adequate conceptual and software tools that allow modular development and software reuse. We present a concept, called capability, which represents a cluster of components of a BDI agent. Capabilities encapsulate beliefs, events and plans while, at the same time, allowing global meta-level reasoning. Capabilities(More)
The water quality of 13 rivers in the lowland, agricultural county of Suffolk is investigated using routine monitoring data for the period 1981 to 2006 collected by the Environment Agency of England and Wales (EA), and its predecessors, with particular emphasis on phosphorus (as total reactive phosphorus, TRP) and total (dissolved and particulate) oxidised(More)
Modern conventional farming provides Western Europe and North America with reliable, high quality, and relatively cheap supplies of food and fiber, increasingly viewed as a potential source of fuel. One of the costs is continued widespread pollution of rivers and groundwater-predominantly by nutrients. In 1970, in both the United States and UK, farming was(More)
Perspective: The Legacy Hypothesis Philip M. Haygarth,*,† Helen P. Jarvie,‡ Steve M. Powers, Andrew N. Sharpley, James J. Elser, Jianbo Shen, Heidi M. Peterson, Neng-Iong Chan, Nicholas J. K. Howden, Tim Burt, Fred Worrall, Fusuo Zhang, and Xuejun Liu †Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, U.K. ‡Centre for Ecology and(More)
This paper sub-samples four 35 year water quality time series to consider the potential influence of short-term hydrological variability on process inference derived from short-term monitoring data. The data comprise two time series for nitrate (NO(3)-N) and two for DOC (using water colour as a surrogate). The four catchments were selected not only because(More)
A good quantitative understanding of phosphorus (P) delivery is essential in the design of management strategies to prevent eutrophication of terrestrial freshwaters. Most research to date has focussed on surface and near-surface hydrological pathways, under the common assumption that little P leaches to groundwater. Here we present an analysis of national(More)
Long records of river water quality are invaluable for helping to understand the biogeochemistry of hydrological systems. They allow relationships to be established between changes in water quality (including seasonal cycles, episodic responses and long-term trends) and potential drivers, such as climatic forcing or human activity; they can act as a(More)
This paper analyses time series of nitrate concentration for 35 sites throughout the Frome and Piddle catchments in southern England for the period 1978--2007. The Piddle catchment lies wholly within the Chalk aquifer in its upper reaches, whereas the headwaters of the Frome are a mixture of Chalk and other lithologies; both rivers flow across Palaeogene(More)
Fluvial dissolved nitrogen (dissolved organic nitrogen [DON], nitrate and ammonium) fluxes from the terrestrial biosphere of the UK to surrounding oceans are explained on the basis of combined predictions of soil to water transfer and in-stream loss. The flux of different nitrogen species from land to surface waters is estimated using an export coefficient(More)
In this study, we conduct a spatial analysis of soil total phosphorus (TP), acid extractable phosphate (PO4) and the stable oxygen (O) isotope ratio within the PO4 molecule (δ18OPO4 ) from an intensively managed agricultural grassland site. Total P in the soil was found to range from 736 to 1952 mg P kg- 1, of which between 12 and 48% was extractable using(More)
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