Computational atmospheric dispersion modelling involves the mathematical simulation of pollutant dispersion in the atmosphere. Dispersion modelling involves the use of computer models that solve mathematical equations and algorithms to simulate pollutant dispersion based on factors such as source characteristics, meteorology and terrain.
Air Noise Environment utilise dispersion models to predict receptor concentrations of air pollutants, particulates and odours emitted from a wide range of sources such as industrial plants, construction sites and vehicular traffic. Atmospheric dispersion models are generally used in circumstances where a new development is proposed, hence cannot be monitored. In addition, due to the relatively high cost of ambient air quality monitoring over the medium to long term, Air Noise Environment often uses atmospheric dispersion modelling as a tool to assess pollution dispersion under a full suite of meteorological conditions (typically hourly meteorological conditions over a year or more) to assess the likelihood of compliance with regulatory requirements for existing operations.
Data inputs to atmospheric dispersion models generally include:
- meteorological conditions such as wind speed and direction and descriptors of atmospheric turbulence.
- emissions parameters such as source location and height, source vent stack diameter and exit velocity, exit temperature and mass flow rate.
- terrain elevations in the area of interest.
- the location and physical dimensions of any obstructions (such as buildings or other structures which could affect the flow of emissions) in the vicinity of the source.
Many of the modern, advanced dispersion modeling programs include a pre-processor module for the input of raw meteorological and other data, hence allowing site specific meteorological data assimilation and location specific meteorological predictions to be completed. Atmospheric dispersion model data output options include contour plots of pollution concentrations at ground and above the ground, statistical analysis (eg, percentile results for odour assessments), and time histories of predicted pollution concentrations at individual receptor positions.
The air dispersion models currently operated by Air Noise Environment include:
- Townsville Ocean Terminal Project: air dispersion modelling for the construction and operational phase of this major residential and cruise terminal development. Completion of background ambient air quality monitoring, including continuous gas sampling for a three month period to confirm industry contributions to the existing local environment. A significant component of the project was on-going liaison with the regulatory agencies with respect to achieving appropriate air quality at the residential portion of the development, particularly with respect to metal concentrations.
- Cross City Tunnel, Airport Link Northern Busway Project, Eastlink Motorway, Victoria Park Tunnel, Waterview Connection (Auckland), M5 East Motorway: air dispersion modelling of emissions from ventilation station outlets and associated road and/or ambient contributions for these major tunnel infrastructure projects.
- PNG Gas Pipeline - air quality dispersion modelling of emergency release of gases, operational and construction emissions to air.
- Proposed Ethanol Plant, development of emissions inventory and air dispersion modelling of potential odour, gaseous and particulate emissions.
- Rendering plant at Toowoomba - odour modelling and assessment, development of control solutions and odour validation testing during the early operational phase for the plant.
Results of computational meteorological modelling, showing wind directions and speeds for a coastal location in the Northern Territory