Zhou Qiaohong

Effects of residual aluminum flocculant on aluminum salt distribution of water and sediment in West Lake (Hangzhou)

Aluminum salt content in the water body and sediment of Hangzhou West Lake was investigated to study the effects of re⁃ sidual aluminum flocculant on aluminum salt content of water, sediment and attachments on submerged macrophyte. The results show that: (1) Aluminum ion content of water inlets is higher than that of the central lake, which caused by residual aluminum flocculants from Diversion Project, while Al2O3 content of sediment tend to be distributed evenly across the lake and is not affected by the Diversion Project; (2) With the flow velocity of about 0.04 to 0.20 m / s, submerged macrophyte can easily become attach⁃ ment receptors to residual aluminum flocculate, but is slightly weaker than sediment in the ability of attaching Al2O3 content; (3) Aluminum ion content of water is high in autumn and winter, which may potentially cause greater biological harm to aquatic organ⁃ ism in the lake. Therefore, it is important to restore submerged macrophyte in autumn and winter seasons. Effect of Diversion Pro⁃ ject on the West Lake water body is essential but unpredictable. It should be possible to reduce the negative impact of Diversion Project. The use of flocculant can be reduced or environmentally friendly flocculant can be chosen instead, and appropriate aquatic plants may be cultivated near water inlets.

Effects of Acetic Acid on Germination and Growth of Turions of Potamogeton crispus and Fragments of Elodea nuttallii

Anaerobic digestion of organic matters in eutrophic lake sediment produced acetic acid. Germination and growth of turions of Potamogeton crispus and fragments of Elodea nuttallii under acetic acid stresses were investigated. The propagules were exposed to acetic acid from 1 to 16mmol/l for a period of 3 or 6 days, and were subsequently cultured in absence of acetic acid. Most E. nuttallii could germinate at concentration of 1mmol/l, but the growth was significantly inhibited. No E. nuttallii could survive after exposures to 4mmol/l or over. 63.3% of P. crispus survived in the exposure to 8mmol/l for 3 days. However, the stronger stresses caused death of P. crispus. Results indicated that P. cripus was more tolerant to acetic acid than E. nuttallii, and that presence of acetic acid in sediment may cause great difficulties in reestablishing submerged macrophytes in eutrophic lakes.