Comparison of aerosol characteristics during haze periods over two urban agglomerations in China using CALIPSO observations

Using CALIPSO （cloud-aerosol lidar and infrared pathfinder satellite observation） vertical observation data during haze periods from January 2007 to December 2008, we analyzed differences in aerosol char- acteristics near the surface, as well as in the middle troposphere between the Beijing-Tianjin-Hebei metropolitan region （Area A） and the Yangtze River Delta region （Area B） in China. One significant dif- ference was that haze pollution in Area A was related to local and non-local aerosols, while in Area B it was related to local anthropogenic sources. In all seasons apart from autumn, aerosol pollution in Area A was more severe than in Area B, both near the surface and at higher altitudes, In Area A, non-spherical aerosols were dominant from 0 to 4 km in spring, summer, and winter; while in autumn, there were con- siderably high numbers of non-spherical aerosols below 0.5 km, and near-spherical aerosols from 0.5 to 4 km. In Area B, both near-spherical and non-spherical aerosols were common in all seasons. Moreover, aerosols with attenuated color ratios of 0-0.2 were more common in all seasons in Area A than in Area B, indicating that fine particle pollution in Area A was more serious than in Area B. Finally, relatively large aerosols linked to gravity settling appeared more frequently near the surface in Area A than in Area B.

Theoretical investigation on submicron particle penetration through circular tubes inside a porous medium

The analytical infinite series solution of submicron particle transport in a circular tube bounded by a porous wall,such as a pinhole,is determined under the slip velocity boundary condition,and the solution is verified by using the experimental data in the previous studies for the specific cases.The results show that particle penetration rate increases with the increase of the porous parameter,the axial pressure drop,and the pinhole radius,whereas it decreases with increasing the pinhole length.The penetration rate of nano-particles are more sensitive to the variation of these parameters.However,the differences between the penetrations of particles ranging from 0.3μm to 1μm are not evident because the diffusion becomes weak gradually in this size range.In addition,a further comparison is performed between the analytical solution and the existing studies,and approximate expressions are presented for accurate calculation of particle penetration rate through pinholes appearing in porous materials including filter devices and masks.