1. Environmental Systems Engineering Program,Faculty of Engineering, University of Regina, Regina, SK, Canada, S4S 0A2. Phone: 306-585-4095; Fax: 306-585-4855; E-mail: gordon.huang@uregina.ca
2. Chinese Research Academy of Environmental Science, North China Electric Power University, Beijing 100012-102206, China.
3. Environmental Systems Engineering Program, Faculty of Engineering, University of Regina, Regina, Sask., Canada S4S 0A2.
4. College of Environmental Engineering and Science, Hunan University, Changsha, Hunan, China 410082.