1. Research Assistant, Sino-Canada Resources and Environmental Research Academy, North China Electric Power Univ., Beijing 102206, China.
2. Professor, Sino-Canada Resources and Environmental Research Academy, North China Electric Power Univ., Beijing 102206, China (corresponding author).
3. Professor and Canada Research Chair, Environmental Systems Engineering Program, Faculty of Engineering and Applied Science, Univ. of Regina, Regina, SK, Canada S4S 0A2.