A comparison of air particulate matter and associated polycyclic aromatic hydrocarbons in some tropical and temperate urban environments

A 12 month study of urban concentrations of total suspended particulates (T SP) and 20 polycyclic aromatic hydrocarbons (PAH) was carried out in Seoul( South Korea), Hong Kong, Bangkok (Thailand), Jakarta (Indonesia) and Melbou rne (Australia). Concentrations of particulate matter in the atmosphere var ied widely between the cities over the course of the study, ranging from a low of 24.1 mu g m(-3) in Melbourne during the winter to a high of 376.2 mu g m(-3) in Jakarta during the dry season. Seasonal variations in both TSP and PAH were observed in the tropical cities in the study with higher conce ntrations during the dry season and lower concentrations during the wet sea son. TSP and PAH concentrations are correlated with each other in these cit ies, suggesting that they have related sources and sinks for these cities. In the temperate cities of Melbourne and Seoul, PAH concentrations were hig her during the cold winter season and lower during the warm summer. However , TSP was quite variable over the years in these latter cities and no clear seasonal trend was observed. A number of factors have been investigated wh ich could be contributing to seasonal variations in pollutant levels, In th e temperate climates, increased emissions due to the use of fossil fuels fo r heating in the winter is evident. However, an interrogation of the databa se with respect to the other factors such as (1) increased photolytic degra dation during the summer, 12) transport of pollutants from other sources, ( 3) removal of PAH via wet deposition and in-cloud scavenging mechanisms and (4) volatilisation of lower molecular weight species during periods of hig h temperature indicates the importance of multiple processes. Even though t here are clearly much lower levels of both particulates and PAH in the wet season of the tropical climates, no statistically significant correlations have been observed between rainfall levels and pollutant concentrations. (C ) 1999 Elsevier Science Ltd. All rights reserved.