UK Smoke and Sulphur Dioxide Network

Network Objectives
The UK Smoke and Sulphur Dioxide (SO₂) Network (Figure 1) serves two purposes. Firstly, to monitor compliance with the relevant EC Directives on sulphur dioxide and suspended particulate matter. The original Directive, 80/779/EEC¹, has been in force since 1980 but is to be superceded in future years; the European Commission have issued a Directive on the Assessment and Management of Ambient Air Quality ² - the so-called "Framework Directive". "Daughter Directives" for pollutants including SO₂ and suspended particulate matter are being developed under the "Framework Directive", and reached Common Position stage in summer 1998³. However, the standards for suspended particulate relate to PM₁₀, not black smoke. The existing standards for monitoring of black smoke will remain in force until 2005.

Secondly, the Network is intended to provide a long-term database of smoke and SO₂ measurements to assess trends in concentration and spatial distribution. For this purpose, a "core" subset of sites is used to provide a representative sample of monitoring locations in major population centres throughout the UK, with a wide spatial coverage of the whole country, as recommended recently by an independent review⁴. A total of 204 Network sites (see Figure 1) were in operation during part or all of the period April 1997 to March 1998. Of these sites, 141 comprised the "core" subset used to provide national statistics. These figures include those sites operating for only part of the year, eg. those which started or ceased operation during this period. It should be emphasised that, in formally assessing smoke and sulphur dioxide concentrations by comparison with the limit and guide values of the EC Directive, analysis of all sites in the UK is undertaken.