Efficient tools for analysing the influence of sources and meteorology on urban ambient concentration trends illustrated for Canberra, Australia

The application of basic tools for the management of urban air quality is illustrated for Canberra, Australia. Pollutants examined are carbon monoxide, nitrogen dioxide, total suspended particulates and fine particles. The calibration of generalised box models requiring only windspeed inputs and pollutant measurements is used to help quantify the relative strengths of the source types. The box models can also be combined with other source quantification techniques such as the construction of emission models for historical or projected traffic patterns. By adopting reasonable assumptions, it is shown that parametric probability functions can be fitted to annual or seasonal frequency distributions of pollutant data. These are used to infer underlying trends when observation periods contain uniformly or randomly missing measurements. For conservative pollutants, annual or seasonal trends can be further adjusted on the basis of meteorology. Thus the trends are reconstructed to show normalisation for the least favorable dispersive year. This provides a check on the effectiveness of emission control strategies on a seasonal basis each year. Finally, it is demonstrated that simple contour plots portraying the diurnal and seasonal variation of pollutant measurements and surface windspeed records can yield a very useful qualitative understanding of both the strength of different emission source types and the effect of seasonal variations in meteorology on those measurements.