The sources and characteristics of atmospheric particulates during the wet and dry seasons in Hong Kong
Air pollution is a serious problem in Hong Kong due to the very high density of diesel powered engines and population as well as the geographical location, which places it under the significant influence of the Asian monsoon with the SW summer monsoon bringing clean oceanic aerosols and the NE winter monsoon bringing polluted continental emissions. To better characterize and obtain a picture of aerosol sources and transport, various techniques, including organic and inorganic tracers, SEM (Scanning Electron Microscope) micrographs, and lead isotopes in TSP (total suspended particulates) and size-fractionated aerosols, were applied in this study. The concentration and composition of aerosols in Hong Kong were significantly influenced by the large-scale meteorological patterns. In the wet season, lower levels were possibly due to greater precipitation, better dispersion, and significant contributions from coarse particles from the sea. Higher concentrations of crustal, flyash, pollution, and plant- wax materials were observed in the dry season. Examining chemical species in different sizes indicated the change of aerosol sources from the local sources in Hong Kong in the wet season to more aggregated materials in the transition period, and to stronger pollution emissions from the Asian continent in the dry season. Conventional factor analysis and chemical mass balance methods identified the sources of Hong Kong aerosols as marine, crustal, oil burning, coal, and incineration. The contributions from pollution and loess increased in the dry season. Oil burning was a stable factor and persisted through the wet and dry seasons, indicating that it was mainly from local sources. The majority of the mass of fine particle pollution elements such as Pb, Sb, and V was removed by wet scavenging, while dry and wet deposition were important for the coarser marine and crustal elements. Particle size as well as meteorological conditions can affect deposition velocities and dry fluxes. By comparing the direct and indirect or modeled fluxes, which differed by a factor of 7, a ``bucket effect'' was suggested to be responsible for the higher measured fluxes for pollution elements.
- Pub Date:
- Physics: Atmospheric Science, Environmental Sciences