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 Energy and Environment and State Key Laboratory of Marine Pollution City University of Hong Kong Hong Kong SAR 999077 P. R. China
3. School of Chemical Engineering and Light Industry Guangdong Key Laboratory of Plant Resources Biorefinery Guangdong University of Technology Guangzhou 510006 P. R. China