1. Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region Ministry of Education School of Water and Environment Chang'an University Xi'an 710064 P. R. China
2. School of Chemical Engineering and Light Industry Guangdong University of Technology Guangzhou 510006 P. R. China
3. Guangdong Key Laboratory of Plant Resources Biorefinery Guangdong University of Technology Guangzhou 510006 P. R. China