PM size distribution in Southern China

As there have been closer economic ties between Hong Kong and the Pearl River Delta region, air pollution problems are inevitably affecting both sides as an entire regime. Respiratory malfunctioning and visibility impairment are related to particulate matters (PMs). However, studies show that the fine size of PMs, rather than their mass, determines how deep the PMs could penetrate the nostril into the respiratory system. The size, especially when near or within the range of wavelength of visible light (0.4-0.7 μm), happens to be most effective in scattering incoming sunlight, so that any object is poorly illuminated. To combat the PM problem, Hong Kong University of Science & Technology (HKUST) and Peking University (PKU) jointly conducted a measurement campaign in hope of understanding the size of ambient PM (Huang et al., 2006). With the help of positive matrix factorization (PMF), they resolve the bulk mass into condensation, droplet and coarse modes. They concluded the following. Ca is in predominant coarse mode, occurring as soil particles. Na is also predominant coarse mode in sea salt, but a small fraction also occurs in droplet mode, which correlates moderately with droplet mode K. The moderate correlation suggests biomass burning source for the droplet Na and K. The biomass burning is also the major source for water soluble organic carbon (WSOC). Sulfate is mainly droplet mode, and the majority of it is formed through aqueous chemical reactions in cloud water. The similar aqueous pathway also applies to oxalate predominantly in droplet mode, however, it could be adsorbed onto alkaline coarse particles. When air quality modeling system was set up adequately, we attempted to compare our model results with the measurement data in hope of understanding aerosol chemistry as well as