Report on the Study to Evaluate Air Pollution Episodes and Intermittent Control Measures

Abstract

Discussions within COGAR during 1981 indicated that collective information on the types of meteorological conditions when large single sources like power stations contributed to pollution episodes, the frequency with which they occurred, and the implications for intermittent control procedures was important for all member utilities. This paper summarises the findings of a working group set up by COGAR to study these problems.

Results indicate that most episodes are still attributable to low or medium level sources rather than large industrial plant. The worst cases in flat terrain where power stations do contribute for many hours involve either stagnant conditions persisting for more than 24 h or a steady wind blowing consistently from an area containing several stations. Single stations can present problems when topography interferes with dispersion or stack height is inadequate for the emission.

Data on the frequency with which episodes occur and the probability of predicting these conditions correctly are needed to evaluate whether intermittent control measures like fuel switching are an effective option. The study showed that it is necessary to measure the vertical structure of the atmosphere as well as ground level concentrations of pollutant. In complicated topography, measurements of the three-dimensional distribution of the pollutant must also be made.

Co-ordination Group for Atmospheric Research UNIPEDE/CORECH