[1] Shaanxi Univ Sci & Technol, Sch Environm Sci & Engn, Xian 710021, Peoples R China
[2] Ningxia Univ, State Key Lab High Efficiency Utilizat Coal & Gre, Yinchuan 750021, Ningxia, Peoples R China
[3] Chinese Acad Sci, Inst Earth Environm, State Key Lab Loess & Quaternary Geol, Xian 710049, Peoples R China
[4] Univ Ghent, Fac Engn & Architecture, Dept Appl Phys, Res Unit Plasma Technol, Sint Pietersnieuwstr 41-B4, B-9000 Ghent, Belgium