1. School of Environment and Safety EngineeringNorth University of China Taiyuan Shanxi 030051 P. R. China
2. Sichuan HuaChuan Indistries Co., Ltd Chengdu Sichuan 610106 P. R. China
3. Urban and Environmental Science DepartmentBinZhou University Binzhou Shandong 256600, P. R. China