Atmospheric Emissions

• Atmospheric dispersion modelling
• Gas and vapour monitoring
• Flux box surveys
• Health risk assessment
• Vapour emission risk assessment
• Assessment of risks to development
• Odour assessment and control

MJCA staff are experienced in the assessment of the impact of pollutant releases to air from a variety of industrial point sources and diffuse sources such as contaminated land, landfill sites, gasification plant and thermal desorption treatment processes. Air dispersion modelling is carried out using a variety of analytical and numerical models including ADMS^TM. The effects of changes in terrain, the presence of structures and the effect of chemical reactions in the plume are incorporated in the assessment.  For the purpose of supporting Environmental Permit applications for point source emissions such as industrial facilities, waste to energy plant such as incinerators and anaerobic digestion facilities and treatment plant emissions to air are estimated and modelled based on close discussions with the equipment manufacturers. For the purpose of supporting Environmental Permit applications for landfill sites the emissions to air of landfill gas components are estimated using the Environment Agency GasSim model.

Based on the modelled emissions of atmospheric contaminants the long term and short term exposure concentrations at sensitive receptors are predicted. Potential exposure is assessed against health based criteria, nuisance based criteria such as odour potential and relevant air quality standards. Advice is provided on mitigation measures where necessary.

We have developed the equipment and expertise to measure emissions of gases or vapour to ambient air from the ground surface using flux boxes. The resultant data are used to predict on or off site ambient air concentrations of the relevant gases for quantitative health risk assessments or for the assessment of odour effects. The data are used also for pollution inventory reporting.

The flux boxes, also known as flux chambers, are used as passive collectors. Gas concentrations are recorded in the field using a variety of instruments and techniques. Field instruments used include flame ionisation detectors, photo ionisation detectors, infra red gas analysers and portable gas chromatographic analytical equipment. Samples are taken in containers such as Tedlar bags or Gresham tubes or are collected on absorption tubes for laboratory analysis.

The effects of gaseous emissions from the ground surface on human health and on development are assessed using a range of quantitative risk assessment models.