1. Chinese Research Academy of Environmental Sciences, Beijing 100012, P.R. China. Fax: +86-10-84913946, E-mail: xibeidou@263.net
2. EVSE, Faculty of Engineering, University of Regina, Regina S4S 0A2, Canada
3. College of Environmental and Energy, Beijing University of Technology, Beijing, 100022, People's Republic of China
4. Chinese Research Academy of Environmental Sciences, Beijing 100012, People's Republic of China, China