Yanming Kang

Vertical distribution of ambient aerosol extinctive properties during haze and haze-free periods based on the Micro-Pulse Lidar observation in Shanghai

Ambient aerosols make a significant contribution to the environment and climate through their optical properties. In this study, the aerosol extinction coefficient and Aerosol optical depth (AOD) retrieved using the Fernald Method from the ground-based Micro-Pulse Lidar (MPL) were used to investigate the characteristics of aerosols during haze and haze-free periods in Shanghai. There were 216 haze days including 145 dry haze days, 39 damp haze days and 32days of both dry and damp haze in Shanghai from March 2009 to February 2010. During the haze periods, aerosols were concentrated mainly below 600m resulting in the most severe pollution layer in Shanghai. In contrast to the aerosol optical properties during haze-free periods, aerosol extinction coefficients and AOD were larger in the lower altitude (below 1km) during haze periods. The lowest 1km contributed 53-72% of the Aerosol optical depth (AOD) below 6km for the haze periods and <41% of that for the haze-free periods except summer. According to the analysis of influencing factors, although atmospheric convection was strong in summer which led to reduce the extinction, the highest occurrence of haze with relatively low aerosol extinction most of time was in summer, which resulted from the factors such as higher relative humidity, temperature and more solar radiation causing hygroscopic growth of particles and formation of secondary aerosols; in spring and autumn, there was less haze occurrences because the boundary layer was relatively higher, which allowed pollutants to diffuse more easily, but spring was the second most frequency season of haze due to frequent dust transport from the north; in winter high concentrations of particles and low boundary layer height were not beneficial to the diffusion of pollutants near the surface and caused haze occurrence rather high with high aerosol extinction.

Indoor environmental quality of high occupancy dormitory buildings in winter in Shanghai, China

Maintaining acceptable air quality and providing adequate thermal comfort are conflicting goals for ventilation requirements in crowded, unheated rooms in winter. The former requires a maximal ventilation rate for indoor pollutant removal, but the latter prefers a minimal rate. To understand the indoor thermal environment in winter in the climatic zone that features hot summer and cold winter, the indoor environmental quality in three selected rooms of university dormitory buildings with high occupancy density in Shanghai, China was monitored simultaneously and continuously from December 2010 to January 2011. The results show that, without space heating equipment in winter, the quality of indoor thermal environment in the student dormitory was poor, and that the indoor temperature ranges of the sampling rooms were completely out of the thermal comfort zone as defined by ASHRAE. To maintain an endurable thermal environment, the occupants had to close the windows to reduce the heat loss, which resulted in elevated indoor CO2 concentrations during sleeping hours due to a lack of ventilation. The indoor CO2 levels exceeding 2000u2009ppm (4000u2009mg/m3) were observed in several occasions. To improve the indoor air environment, central heating systems or individual heating units should be provided for dormitory buildings in the Yangtze River Delta region.

Numerical analysis of the dynamics of aerosol inertial collection and aggregation on raindrops

ABSTRACT A three-dimensional stochastic model is developed for predicting atmospheric aerosol collection and aggregation on the surface of a falling raindrop at its terminal velocity. Potential flow and viscous flow are assumed as the flow fields in the vicinity of the large and the small raindrops, respectively. The results show that hydrophobic coarse mode aerosols collected by either small raindrops (dc < 100 μm) or large drops (dc > 100 μm) form aggregations on the surfaces of drops, and accumulation mode aerosols tend to be captured by the aggregations or hydrophobic coarse particles which have been collected by the drops, and this may significantly enhance the capability of the raindrop for fine aerosol collection. When the aggregation effect is considered in the calculation, fine aerosol efficiency can be promoted by one to two orders of magnitude. Therefore, fine particle collision efficiency by raindrops is underestimated by employing the classical dynamic theory which neglects the particle aggregation effect. However, the collection efficiency of coarse particles remains almost constant with the increase in the amount of particles collected by large drops, while there is only a slight increase in efficiency by small raindrops upon increasing in particle concentration. This implies that the traditional limiting trajectory method can still be used for the calculation of coarse particle collection efficiencies by either small or large raindrops. Copyright

Simulations of the impacts of building height layout on air quality in natural-ventilated rooms around street canyons

Numerical simulations were conducted to investigate the effects of building height ratio (i.e., HR, the height ratio of the upstream building to the downstream building) on the air quality in buildings beside street canyons, and both regular and staggered canyons were considered for the simulations. The results show that the building height ratio affects not only the ventilation fluxes of the rooms in the downstream building but also the pollutant concentrations around the building. The parameter, outdoor effective source intensity of a room, is then proposed to calculate the amount of vehicular pollutants that enters into building rooms. Smaller value of this parameter indicates less pollutant enters the room. The numerical results reveal that HRs from 2/7 to 7/2 are the favorable height ratios for the regular canyons, as they obtain smaller values than the other cases. While HR values of 5/7, 7/7, and 7/5 are appropriate for staggered canyons. In addition, in terms of improving indoor air quality by natural ventilation, the staggered canyons with favorable HR are better than those of the regular canyons.

Field measurement of winter air quality of the typical rural building in southwest of Shandong Province

For investigating the winter air quality of the typical rural building in southwest of Shandong province, concentrations of particles (PM1.0), gaseous pollutants (CO and CO2) in the main room and courtyard were measured. Concentrations of contaminants in both rooms appeared consistent trend, with peak values in the three periods of mealtimes. Contaminants in the main rooms mainly derived from the courtyard, as well as contribution of occupants activity. Using stove to warm the main room produced substantive gaseous contaminants, especially higher concentration of CO when stove was quenching. Comparing biomass and fossil fuel, the former produced more particles, while the latter made more gaseous pollutants. In addition, setting off fireworks seriously contaminated air quality of rural buildings, and concentrations of contaminants depended on the patterns of fireworks.