Simple Calculation of Atmospheric Impact Limits is a suite of screening tools for assessing the impact from agricultural and combustion sources on semi-natural areas like SSSIs and SACs. SCAIL is now available as two models - SCAIL Agriculture and SCAIL Combustion. Both models provide an estimate of the amount of acidity, nitrogen or sulphur deposited on to a habitat or sensitive ecosystem. Output from the models can then be used to assess whether impact limits for the habitat are exceeded or not. The models are useful as an initial screening of sources for IPPC applications or Appropriate Assessments under the Habitats Directive.

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SCAIL AGRICULTURE is a simple online screening tool that can be used in IPPC applications, EIAs or Appropriate Assessments to estimate the effect of an agricultural emission (e.g. poultry shed) on a habitat (e.g. SSSI). This estimate can then be used to determine the exceedance or non-exceedance of the habitat's impact limit and will help users in deciding whether more detailed modelling or site specific investigation is required. The model takes into account regional wind statistics for 15 UK regions and users input details of their source (e.g. livestock numbers), the habitat in question and distance from source to the habitat.

SCAIL COMBUSTION is a screening tool that uses the atmospheric dispersion model AERMOD to model SO2 and NOX emissions from small to medium sized combustion sources. The model estimates the impacts of nitrogen oxides (NOx: NO and NO2) and sulphur dioxide (SO2) emissions on sensitive habitat sites. User can enter details of their habitat, source and stack parameters to calculate an estimate of NOx and SO2, acid and nitrogen deposition at the habitat. The model uses wind data from the nearest meteorological station data, of which there are around 30 meteorological stations in the system.

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