Critical loads of nitrogen and their exceedance in UK freshwaters

In June 1994 the United Kingdom government signed the European sulphur protocol which committed them to a 70% reduction in SO2 emissions by the year 2005 and 80% by 2010, based on 1980 levels. This was the first instance of international legislation being formulated using the critical load concept. Notwithstanding the anticipated benefits to the environment of such reductions it was also recognised that such improvements could be diminished unless a similar approach was used to address the problem of increasing nitrogen emissions. The Freshwater Sub-group of the UK Critical Loads Advisory Group (CLAG) has responsibility for evaluating available techniques for calculating critical loads for nitrogen and for establishing a scientific programme to address key issues and gaps in our knowledge of nitrogen dynamics. This paper summarises the preliminary findings of the Freshwater Group with respect to the nitrogen status and critical loads of UK freshwater

The impact of nitrogen deposition on upland surface waters in Great Britain: a regional assessment of nitrate leaching.

A national dataset of water chemistry collected for critical loads mapping is used to make a regional assessment of surface water nitrate concentrations in Great Britain. The primary data are dominated by high concentrations in lowland regions Where N inputs are dominated by non-atmospheric sources. Land cover data are used to screen out sites with potential catchment sources of N, allowing the evaluation of nitrate leaching due to atmospheric deposition alone. In the screened dataset several upland regions show elevated nitrate concentrations, notably Wales, the Pennines, Cumbria, Galloway and the Cairngorms, and there is a clear relationship between surface water nitrate and total N deposition