The general applicability of a model to control violations of short-term exposure standards for TSP

Abstract

An urban air quality model, referred to here as the TSP hybrid emissions control model, has been successfully applied to Total Suspended Particulate (TSP) data in the city of Brisbane, Australia, by Simpson and Miles (1988, Atmospheric Environment, in press). The model is based on the assumptions that 1. (1) the frequency of total suspended particulate data can be reliably represented by a two-parameter lognormal distribution; and 2. (2) a simple deterministic relationship between percentiles of pollutant concentration and the inverse of wind speed exists for this urban area. These assumptions are tested in this paper at a number of locations in Australia and over a number of years. Assumption 1. (1) is shown to be valid for most sites and years. If invalid the lognormal model may overestimate the maximum concentration by between 12 and 161% where the two-parameter γ distribution is preferred and between 36 and 215% where the two-parameter Weibull distribution best represents the statistical distribution of TSP concentrations. These errors were considerably less at coastal sites and reduced further if only east and southeast coast sites were compared. Assumption 2. (2) has been tested for the same sites and years. A comparison of geometric standard deviations for TSP and the inverse of wind speed demonstrates that the TSP hybrid emissions control model may be as successful in other coastal urban areas of Australia but inland sites may be different. Both assumptions tend to overestimate the annual maximum so the model may be useful in producing a conservative control strategy for particulate emissions which avoids violations of health standards related to short-term exposure. It is also suggested that an average TSP shape parameter may improve model performance and that both modelling assumptions are generally applicable to urban areas where the particulate emissions show little marked seasonal variability.