In September 2009, CASANZ will host the 19th International Clean Air & Environment Conference in Perth. We are currently preparing three presentations for this forum. A brief description of the work to be presented in each paper is presented below. If you are interested in further information or would like to discuss the work further please give the authors a call. They would be only too happy to interpret the technical details for you.
Authors: Alex Schloss and Christine Killip
This study investigates the methodology employed to characterise industrial flares for the purposes of assessing their vertical plume velocity with regard to aviation safety. Katestone Environmental has previously developed a methodology to assess vertical plume velocities using the TAPM meteorological model and empirical methods to assess the enhancement of multiple co-located plumes, in accordance with the Civil Aviation Safety Authority (CASA) guidelines.
The characterisation of flares for modelling is different to that of conventional stacks due to their large buoyancy, short duration, and low frequency discharges. Current characterisation methods using the USEPA Screen 3 model and modelling at hourly time steps tend to generate extremely large hazard zones that can extend above 1000 metres above ground level. Consequently, the assessment of risk to aircraft flying in close proximity to an industrial flare needs both a qualitative and quantitative approach.
Author: Andrew Wiebe
For this study, we explore the relationship between synoptic or large-scale weather patterns and the impacts associated with the dispersion of air pollutants from industrial sources. Using cluster analysis techniques to categorise synoptic weather patterns over Queensland for the past forty years, we identify those conditions that generate the dispersion meteorology resulting in beneficial, neutral and adverse air pollutant dispersion. This knowledge will go a long way in improving the forecasting capabilities of air pollution events.
Author: Andrew Wiebe
The most critical meteorological parameter for the determination of the diffusion and transport of air pollutants is atmospheric turbulence, which refers to the vertical and horizontal mixing of the boundary layer. Turbulence is generated either by heating of the surface sending up thermals (thermal convection) or by frictional forces produced by the roughness of the surface (mechanical turbulence). In dispersion models, the characterisation of both factors is very important, where the area being simulated contains very different surface characteristics, such as coastal environments.
Atmospheric turbulence generated over varying surfaces (e.g., grassland and ocean) in close proximity is not independent of one another, and can be moved (advected) between the two by the wind. This means that turbulence generated overland can be transported offshore, thereby increasing the net turbulence and potential for dispersion of pollutants over water bodies. However, this does not work in the opposite direction where weak turbulence is advected on shore dampening the turbulence over land as it is still a net gain even if it is negligible. Unfortunately this advection of turbulence or momentum flux is not directly modelled by the current suite of coupled meteorological-dispersion models, and has to be added in as a constant. The introduction of such a constant is dependent on many factors, such as the average height of the plume being dispersed, the average wind speed at that height, and the size of the water body.
We have been investigating the influence this constant has on the dispersion of pollutants in a coastal region with some exciting results.