aerosols are fine particle which are ubiquitous in air in either liquid or solid form, are often observed as dust, smoke and haze. Atmospheric haze is now a semi-permanent feature of large cities worldwide, caused by the emission of fine aerosols from industrail and vehicular sources. In Hong Kong, for example, visibility lower than 8 km, which may affect transport safety, noe occurs approximately 20% of the time, having risen at 6% per decade since 1980.