1. Environmental Engineering Department; Nanjing Forestry University; Longpan Rd. 159 210037 Nanjing P.R. China
2. Institute of Macromolecular Chemistry; Academy of Sciences of the Czech Republic; Heyrovský Sq. 2 162 06 Prague 6 Czech Republic
3. Faculty of Mathematics and Physics; Charles University; V Holešovičkách 2 180 00 Prague 8 Czech Republic