A COMPARISON OF MODEL AND OBSERVED NETWORK ESTIMATES OF SULFUR DEPOSITION ACROSS GREAT-BRITAIN FOR 1990 AND ITS LIKELY SOURCE ATTRIBUTION

Long-range transport models for acidic sulphur species are being used to develop emission-control strategies to combat environmental acidifi cation in the remote, sensitive regions of Europe. The incorporation o f seeder-feeder enhancement into a simple trajectory model for sulphur has markedly improved the representation of wet deposition across Gre at Britain, as shown by a detailed comparison of the model results wit h the observations from monitoring networks. An uncertainty analysis r eveals that those input parameters which contribute mast to uncertaint y in the total sulphur deposition are the sulphur-dioxide emissions, w ind speeds and wet-removal coefficients. The total Great Britain dry a nd wet depositions of sulphur are estimated to be 216 and 241 thousand tonnes per year, respectively, making a total sulphur deposition per year of 457 +/- 110 thousand tonnes, in excellent agreement with the o bserved quantity of 433 thousand tonnes. The model was used to give an indication of the origin of the deposited sulphur across Great Britai n. European land-based sulphur sources contribute 34% of the depositio n to Great Britain, with significant dry deposition in south-east Engl and and wet deposition in upland western Britain. UK power stations an d oil refineries contribute 46.7% of total deposition, with shipping a nd natural sulphur sources from algal blooms, a mere 4.6%. Differences in source attribution between this UK-scale. study and those previous ly published for the long-range transport scale are explored and it is concluded that national-scale models have an important role to play i n policy formulation.