Modelling flow and inorganic nitrogen dynamics on the Hampshire Avon: Linking upstream processes to downstream water quality.

Managing diffuse pollution in catchments is a major issue for environmental managers planning to meet water quality standards and comply with the EU Water Framework Directive. A major source of diffuse pollution is from nitrogen, with high nitrate concentrations affecting water supplies and in-stream ecology. A dynamic, process based model of flow, nitrate and ammonium (INCA-N) has been applied to the Hampshire Avon as part of the NERC Macronutrient Cycles Programme to link upstream and downstream measurements of water chemistry.

Fine-scale in situ measurement of riverbed nitrate production and consumption in an armored permeable riverbed.

Alteration of the global nitrogen cycle by man has increased nitrogen loading in waterways considerably, often with harmful consequences for aquatic ecosystems. Dynamic redox conditions within riverbeds support a variety of nitrogen transformations, some of which can attenuate this burden. In reality, however, assessing the importance of processes besides perhaps denitrification is difficult, due to a sparseness of data, especially in situ, where sediment structure and hydrologic pathways are intact.

River bed carbon and nitrogen cycling: state of play and some new directions.

The significance of freshwaters as key players in the global budget of both carbon dioxide and methane has recently been highlighted. In particular, rivers clearly do not act simply as inert conduits merely piping carbon from catchment to coast, but, on the whole, their metabolic activity transforms a considerable fraction of the carbon that they convey. In addition, nitrogen is cycled, sometimes in tight unison with carbon, with appreciable amounts being 'denitrified' between catchment and coast.