(This is a quick reference guide introducing some of the models that are used to model air pollution dispersion from industrial and agricultural sources.)
Introduction
Air dispersion models are used to provide an estimate of a concentration or deposition of a pollutant emitted from an industrial process (point source) or a road (line source). Output from dispersion models are often used to predict the contribution of a new or existing process, to level of pollutants at specified points. The modelled outputs of concentrations and depositions can then be compared with environmental limits (e.g. Critical Loads) and human health air quality limits (e.g. NAQS). There are numerous models that are used for both short-range local scale modelling (<20 km), and long-range, regional/trans-boundary, air pollution (>50km). In this section we mention some that are commonly used in the UK for impact assessments. , but no models are favoured or prescribed. For further information about modelling and IPPC impact assessment see guidance from EA, SEPA, and NIEA.
Typical applications of these models include:
- IPPC authorisations,
- Modelling odour
- Environmental Impact Assessments and
- Appropriate Assessments under the Habitats Directive
ADMS (short -range)
There are a range of ADMS (Advanced Dispersion Modelling System) model versions are used throughout the world, and are used by many UK local authorities and consultancies in assessing industrial pollution and urban air quality management. ADMS 4 is used to model the impact of existing and proposed industrial installations. Current and future air quality can be assessed with respect to the air quality standards such as the EU Air Quality Directive, UK Air Quality Strategy, US National Ambient Air Quality Standards (NAAQS), Chinese Class I, II and III and WHO guidelines.
AERMOD (short -range)
AERMOD is developed by the US Environment Protection Agency in collaboration with the American Meteorological Society. AERMOD is actually a modelling system with three separate components: AERMOD (AERMIC Dispersion Model), AERMAP (AERMOD Terrain Preprocessor), and AERMET (AERMOD Meteorological Preprocessor) which uses meteorological data and surface characteristics to calculate boundary layer parameters (e.g. mixing height, friction velocity, etc.).
SCAIL (short -range)
Simple Calculation of Atmospheric Impact Limits is an online 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 assessments under the Habitats Directive.
FRAME (long -range)
The FRAME (Fine Resolution Atmospheric Multi-pollutant Exchange) model is a Lagrangian atmospheric transport model used to assess the long-term annual mean deposition of reduced and oxidised nitrogen and sulphur over the United Kingdom. The model was developed from an earlier European scale model, TERN (Transport over Europe of Reduced Nitrogen). FRAME focuses on the transport and deposition of reduced nitrogen, sulphur and oxidised nitrogen.
DMRB (short -range)
The DMRB (Design Manual for Roads and Bridges Screening Method) screening tool gives a preliminary indication of air quality near roads. DMRB has been assessed by comparing its results with measurements conducted at a wide range of roadside locations. The DMRB method requires information on vehicle flow, HGV mix, vehicle speed, and receptor-road distances.
CBED (Concentration Based Estimated Deposition) provides an estimate of deposition for key pollutants based on concentraion maps. See http://www.apis.ac.uk/popup/cbed for details.