1. College of Environmental & Energy Engineering, Beijing University of Technology, Beijing 100022, People's Republic of China
2. College of Environmental & Energy Engineering, Beijing University of Technology, Beijing 100022, P.R. China; E-mail: chengsy@bjut.edu.cn
3. Department of Civil and Resource Engineering, Dalhousie University, Halifax, NS B3J 1Z1, Canada; Phone: 902-494-3958; Fax: 902-494-3108; E-mail: Lei.Liu@Dal.Ca
4. Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People's Republic of China