Acknowledgements
This research was supported by the National Natural Science
Foundation of China (Grant No. 50978242), National 863 Program
(2008BADC4B18), and National Water Project (Grant No.
2009ZX07528-006-01).
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.cej.2011.03.020.