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), is most effective in scattering incoming sunlight. Community Multiscale Air Quality Modeling (CMAQ) system is applied to simulation ambient PM size distribution in summer and winter of 2004, driven by meteorology simulated by MM5 (the fifth version of PSU/NCAR mesoscale model) and emission sources in China including Hong Kong.

Size distributions of sulfate, nitrate, ammonia, elemental carbon (EC) and organic carbon (OC) outputted by CM...[ Read more ]

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), is most effective in scattering incoming sunlight. Community Multiscale Air Quality Modeling (CMAQ) system is applied to simulation ambient PM size distribution in summer and winter of 2004, driven by meteorology simulated by MM5 (the fifth version of PSU/NCAR mesoscale model) and emission sources in China including Hong Kong.

Size distributions of sulfate, nitrate, ammonia, elemental carbon (EC) and organic carbon (OC) outputted by CMAQ are compared with ten-stage microorifice uniform deposit impactor (MOUDI) observation during different weather conditions dominating Pearl River Delta (PRD) region. In fine mode CMAQ output PM has a mass median aerodynamic diameter (MMAD) around 0.56-1.0μm, smaller than the observation which is 1.0-1.8μm. In coarse mode, CMAQ output PM has a MMAD around 5.6-10μm, larger than the observation which is around 5.6μm. Since PM precursors are well predicted, it implies that fine mode peak of primary emission is underestimated in CMAQ. Based on latest near source observation in Asia, a new method to define primary emission size distribution (PESD) is established. PESD are calculated based on different source types instead of using one fixed PESD defined in CMAQ. Now simulated PM10 fine mode MMAD and standard deviation match observation, and new CMAQ simulated fine mode MMAD is around 0.56-1μ m. Statistical data shows that new PESD improves PM size distribution of CMAQ. Total PM10 simulation performance index agreement (IA) of old simulation is 0.65, while after PESD is updated, the IA is 0.80. New normalized mean bias (NMB) is 67.9%, also improved with NMB of control run which is 75.6%. PM2.5 simulation is also improved. In new CMAQ simulation over all sites, the NMB and normalized mean average bias (NMGE) values are -3.3% and 75.58%, lower than the respective bias values of 15.18% and 86.74% in control run.