Water, Air, & Soil Pollution: Focus

, Volume 7, Issue 1–3, pp 391–397 | Cite as

Comparison of Critical Load Exceedance and Its Uncertainty Based on National and Site-specific Data

  • Liz HeywoodEmail author
  • Richard Skeffington
  • Paul Whitehead
  • Brian Reynolds


Critical loads have been used to develop international agreements on acidifying air pollution abatement, and within the UK and other countries, to develop national policies for pollution abatement. The Environment Agency (England and Wales) has regulatory obligations to protect sites of high conservation value from the threat of acidification, and hence requires a practical methodology for acidification assessments at the site-specific scale. The Environment Agency has therefore posed the question: Are the national critical load exceedance models sufficiently robust to form the basis for methods to assess harm to individual sites or are they only useful for national policy development? In order to provide one measure of the appropriateness of applying the models at the site-specific scale we incorporated estimates of uncertainty in both national and site-specific data into the calculation of critical load exceedance for individual sites. The exceedance calculations use data from a wide range of sources and the accuracy of the exceedance will be influenced by the accuracy of the input data sets. Using Monte Carlo methods to incorporate the uncertainty in the input data sets into the calculation a distribution of critical load exceedance values is generated rather than a single point estimate. This paper compares uncertainty analyses for coniferous forested sites in England and Wales using both national scale and site-specific data sets and uncertainty ranges.


Acidification Critical loads Robustness Uncertainty Scale Input data Policy 



The authors gratefully acknowledge the Environment Agency (E&W) for their contribution to the funding of this research. However, the views expressed are those of the authors.


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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  • Liz Heywood
    • 1
    Email author
  • Richard Skeffington
    • 2
  • Paul Whitehead
    • 2
  • Brian Reynolds
    • 3
  1. 1.Centre for Ecology and Hydrology, Monks Wood, Abbots RiptonHuntingdonUK
  2. 2.Aquatic Environments Research Centre, Department of GeographyUniversity of ReadingReadingUK
  3. 3.Centre for Ecology and HydrologyBangorUK

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