An air quality baseline assessment for the Vaal Airshed in South Africa

Abstract

The Vaal Triangle is renowned for its highly industrialised activities. With the addition of domestic fuel burning, vehicle exhaust, mining and agricultural activities, the Vaal Airshed has become highly polluted. The concerns of the elevated concentrations in the area were raised by the Department of Environmental Affairs and Tourism (DEAT) when the Vaal Region was declared the first priority area on 21 April 2006. The basis for this declaration includes: areas that exceed or may exceed air quality standards, areas associated with significant air quality impacts and areas requiring specific air quality management actions to rectify the situation. The purpose of this study is to determine the Status Quo of the Vaal Airshed. The emissions inventory for the study area includes industrial operations, mining activities, domestic fuel burning and vehicle tailpipe emissions along major national and regional routes. Priority pollutants (i.e. sulphur dioxide, nitrogen dioxide and inhalable particulate matter) are assessed with the aid of the US Environmental Protection Agency approved CALPUFF modelling suite, a non-steady-state Lagrangian Gaussian puff dispersion model. From the dispersion simulations an air quality impact assessment is undertaken. The major findings of the air quality assessment indicate that particulate concentrations are elevated over most areas of the Vaal Airshed, particularly in residential areas where domestic coal burning occurs and areas neighbouring major industrial operations. Similarly, elevated sulphur dioxide concentrations occur over industrial and domestic coal burning areas. Elevated nitrogen dioxide concentrations have a regional impact over the Vaal Airshed. Priority areas are identified based on the predicted ambient air concentrations from the priority pollutants and exposure potential. Source contributions are investigated based on the extent of their emissions and basis of impacts. Copyright