Aerosol size distributions observed at Naiman in the Asian dust source region of Inner Mongolia

作者：Park Soon Ung^*; Park Moon Soo

来源：Atmospheric Environment, 2014, 82: 17-23.

DOI：10.1016/j.atmosenv.2013.09.054

• Aerosol size distribution
• Asian dust particle
• Dust source region
• Naiman site
• Spectral mass concentration distribution

Aerosol size distributions of observed mass concentrations at the Naiman site in Inner Mongolia that is one of the major Asian dust source regions have been examined for the period from April 2010 to July 2012. The total number of 262 sampled data using the 10-stage quartz crystal microbalance (QCM) cascade impactor is obtained by presetting the frequency changes of 40 Hz during April 2010, 60 Hz for the period of 28 April-16 September 2010 and 70 Hz from I November 2010-29 July 2012. The total mass concentrations (PM10) measured by the QCM cascade impactor are modified to have the same sampling time of 60 min with the help of the 1-h averaged PM10 concentration measured by the beta gauge at the same site. These modified QCM data are classified into the local dust emission case of 196 and the dust advection case of 66. The local dust emission case is defined when the calculated dust flux with the two-level (3 m and 15 m high) measured PM10 concentrations by the beta-gauge is upward and the PM10 concentration measured at 3 m high exceeds 100 mu g m(-3) while all the rest of QCM sampled data are classified as the dust advection case. The results indicate that the spectral mass concentration distribution of the local dust emission case shows a two-modal distribution with one additional mode of the large particle that cannot be resolved by the QCM cascade impactor whereas that of the advection case reveals a three-modal distribution with one additional unresolved large particle mode. The percent spectral mass concentration distribution of the unresolved mode (stage 1) for the local dust emission case is larger than that for the dust advection case. The modal distributions of both cases can be regressed optimally with log-normal distribution functions. The resolved log-normal distribution functions of the mass concentration distribution by the QCM cascade impactor are found to be the particle mean diameter (the standard deviation) of 0.28 (2.07) and 3.15 mu m (1.41 mu m) for the local emission case and 0.16 (1.51), 0.60 (1.41) and 2.88 mu m (1.38 mu m) for the advection case. This clearly suggests that the spectral mass concentration shifts toward the larger particle size for the local emission case.

• 出版日期2014-1