Identification And Quantification OfVolatile Organic Compounds In The Cape TownBrown Haze

Abstract

The formation of a brown haze due to urban pollution is a common phenomenon in many industrialised cities in the world. Cape Town in South Africa is renowned for its scenic beauty but this is marred by a brown haze layer that develops on certain days during inversion and windless conditions in the winter. In order to identify and quantify the temporal and spatial distribution of volatile organic compounds (VOC’s) which are a contributing factor to this phenomenon, TO Canisters and Carbotrap TM 300 tubes were used for this investigation. Samples were taken at six different sites in the Cape Metropolis area, at ground level and at 1000 and 1500 ft above sea level (ASL). In addition, 75 µm PDMS and Carboxen SPME fibres were also used. All samples collected were analysed by GC-MS and the different data sets were compared with each other. The daytime concentrations of the VOC’s appeared to be significantly higher than the night time concentrations. Open-chain hydrocarbons and benzene related compounds were generally found at ground level, while at higher levels of 1000 and 1500 ft above sea level, alcohols and ketone-compounds were detected.