Atmospheric dispersion

Quick links: Non-point sources Source term sensitivity Thompson buildings study GMOs Historical dispersion modelling

CERC was set up to create practical models using the latest developments in the understanding of the dispersion of pollutants in the atmospheric boundary layer. The resulting ADMS suite of models now comprise:

• ADMS 6 for modelling emissions from small numbers of industrial or agricultural sources in detail;
• ADMS-Urban and ADMS-Roads for modelling emissions from urban areas, in particular those from road sources and domestic combustion;
• ADMS-Airport for modelling emissions from urban areas including aircraft take-off and landing emissions; and
• GASTAR, ADMS-STAR and ADMS-Puff for modelling short-term hazardous releases including those of dense gases and radioactive substances.

The principles behind these models, with references to underlying fundamental research publications, are given in the ADMS Technical Specification documents. CERC's understanding of atmospheric dispersion has also been applied to modelling wind turbine wakes and anthropogenic heat emissions.

Dispersion from non-point sources

Many regulated sources have complex geometries near or at ground level, for instance agricultural emissions of ammonia and particulates from pig and poultry farms, litter and manure storage and land spreading. Other 'non-point' sources include composting sites where bio-waste emits fungi and bacteria, for instance from windrows. These sources are usually in rural areas which may be close to protected nature sites, with particular concerns about exposure to pollutants. In addition, agricultural and composting facilities are sources of odour, where the impacts on nearby residential areas must be assessed.

CERC, A S Modelling & Data Ltd. and Professor Akula Venkatram (University of California, CA, US) carried out 'A Review of the Limitations and Uncertainties of Modelling Pollutant Dispersion from Non-point Sources'. This work was funded by the UK Atmospheric Dispersion Modelling Liaison Committee (ADMLC). The report presents a detailed literature review and results from four validation studies (focussing on ADMS and AERMOD); it also includes a good practice guidance section. The report describing the outcomes of this review was published in April 2016 and is available for download from the ADMLC publications webpage. Some of this work was presented at the 17^th conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes; the extended abstract describing this work is also available.

Source term sensitivity

Defining source terms is an essential part of dispersion modelling. A substance can be released into the atmosphere in many different ways, particularly in accidental release situations. It is important to have an understanding of the sensitivity of the model results to each of the source term input parameters. CERC and GT Science & Software Ltd carried out a 'High Level Review of the Sensitivity of Dispersion Model Predictions to Individual Source Term Parameters'. This work was funded by the UK Atmospheric Dispersion Modelling Liaison Committee (ADMLC).

The review discusses the main issues of source term sensitivity, describes a range of commonly-used dispersion models, and presents the results of detailed sensitivity tests. The source terms examined in the review include evaporating pools, catastrophic failures of pressurised vessels, jet releases, spray releases, warehouse fires and pool fires. The report describing the outcomes of this review was published in January 2017 and is available for download from the ADMLC publications webpage.

Evaluating ADMS buildings dispersion module using Thompson study

Detailed data from the Thompson study of dispersion from sources near buildings have been used to evaluate and improve the ADMS buildings dispersion model. This wind tunnel study used four different building geometries and multiple source locations relative to each building geometry to examine the variation of buildings effects on dispersion. ADMS model performance has been evaluated against the whole dataset and also in detail for each buildings geometry in order to identify potential improvements to the ADMS model code.

Dispersion study of GMOs

CERC was a partner in the EU Framework 6 project SIGMEA with the goal of Genetically Modified Organism (GMO) mapping across Europe. ADMS with its advanced treatment of area sources was used for the dispersion modelling aspects of the problem. CERC also carried out investigations into the dispersion of pollen for Ministry for Agriculture, Fisheries and Farming (MAFF), now part of Defra. The work is reported in the publication below.

Learn more

• Walklate PJ, Hunt JCR, Higson HL and Sweet JB,2004:A model of pollen-mediated gene flow for oilseed rape.Proc. R. Soc. Lond. B March 7, 2004 271:441-449, DOI 10.1098/rspb.2003.2578 (Royal Society website)

Historical dispersion modelling

Economics researchers at the University of Bristol have investigated the impact of industrial pollution during the Industrial Revolution on the social structures of English cities. To inform the research, CERC ran ADMS 5, using statistical meteorological data, to generate pollution footprints for over 50 English towns and cities at the peak of the Industrial Revolution. Dr Stephan Heblich, Dr Alex Trew and Dr Yanos Zylberberg then combined the pollution distributions with census data to investigate the persistence of social divisions relative to pollutant concentrations. The results of the research were published in 2016.