Atmospheric deposition of sulphur and nitrogen species in the UK

1. The foundations of our understanding of acid deposition were laid in the last century, but the scale and scope of damage to sensitive receptors has only been subject to intensive investigation over the last 30 years or so. Negotiations are now well underway to reduce emissions, and for some pollutants policy is in place, so that these receptors may be protected adequately. Crucial to this has been the 'critical loads' approach adopted in the U.K. and elsewhere in Europe over the last 6 years. 2. This paper describes the source of acidic emissions, how these emissions are transformed in the atmosphere and subsequently deposited. Measurements of wet deposition are made at a number of sites in the U.K. and some of the results from the networks are presented. These results allow wet and dry deposition to be mapped and the methodologies and underlying assumptions to these procedures are described, and S deposition has been estimated for the U.K. Acid Waters Monitoring Network sites.