ERCIM News No.34 - July 1998

Operational Air Pollution Modelling

by Tiziano Tirabassi

Air quality management and protection require a knowledge of the state of the environment encompassing both cognitive and interpretative elements. The monitoring network, together with the inventory of emission sources, is of fundamental importance for constructing the cognitive framework but neglects the interpretative one. Efficient air pollution management must dispose of interpretative tools which are able to extrapolate in space and time the values measured where analysers are located. However, the improvements to the atmosphere can only be obtained using plans that reduce emissions ie by means of instruments (like air pollution models) able to link the causes (source emissions) of pollution to the related effects (air pollution concentrations). We describe a set of air pollution models developed at the Istituto per lo Studio dei Fenomeni Fisici e Chimici della Bassa e Alta Atmosfera (FISBAT-CNR).

In practice most of the estimates of dispersion of air pollution from continuous point sources are based on the Gaussian approach. A basic assumption for the application of this approach is that the plume is dispersed by homogeneous turbulence. However, due to the presence of the ground, turbulence is usually not homogeneous in the vertical direction.

Various organisations world-wide are currently introducing new advanced modelling techniques based on the results of recent research on the meteorological state of the boundary layer. These advanced modelling techniques contain algorithms for calculating the main factors that determine air pollution diffusion in terms of the fundamental parameters of the atmospheric boundary layer, such as the Monin-Obukhov length scale and friction velocity. Experimental work and modelling efforts have attempted to parameterize the surface fluxes of momentum, heat and moisture in terms of routinely measured meteorological parameters.

Model Codes

Within this framework, several model codes employing a non-Gaussian analytical solution of the advection-diffusion equation have been developed at FISBAT-CNR, Bologna:

The SPM model has been used in a project between Italy and Brazil to investigate the dispersion of radionuclides from the Brazilian Navy's industrial installation 'Centro Experimental ARAMAR' (CEA) located in Iperó, in a rural region of the State of São Paulo.

The performance of the models has been assessed with success in cases of both ground level sources, using data of the Prairie Grass experiment , as well as elevated sources, using data from the EPRI experiment at Kincaid power plant and from the Copenhagen data set. In addition, performance in the case of complex terrain has been evaluated using wind tunnel data from the Fluid Modelling Facility of the US Environmental Protection Agency, Triangle Park (North Carolina).

Please contact:

Tiziano Tirabassi - FISBAT (CNR)
Tel: +39 051 63 99 601
E-mail: tirabassi@area.bo.cnr.it

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