Study On The Purification Of Vallisneria Spinulosa For Aquatic Plants To Different Eutrophic Water

This paper aimed to study the function of Vallisneria spinulosa and other six aquatic plants in the purification of eutrophic water. The results were as follow.1. By the determination of related growth increment of aquatic plants cultured in two different eutrophic waters, the results showed that seven aquatic plants such as V. spinulosa could grow normally. Among all the 7 aquatic plants, Ceratophyllum demersum, Ipomoea aquatica and Eichhornia crassipes could grow well in eutrophic water. Oenanthe clecumbens and Typha latifolia were suitable for abnormal eutrophic water. The growth condition of Elodea Canadensis and V. spinulosa in two different eutrophic waters were basically the same.2. In the research of the purification of eutrophic water, removal effects for N and P of aquatic plants were especially important. In the study, the removal effects for N and P of aquatic plants cultured in the abnormal eutrophic water were ranked as follows: V. spinulosa> O. clecumbens> T. latifolia> E. Canadensis > C. demersum > E. crassipes > I. aquatica . The removal effects for N and P of aquatic plants cultured in the eutrophic water were ranked as follows: C. demersum > V. spinulosa > I. aquatica > E. crassipes > E. Canadensis > O. clecumbens > T. latifolia. V. spinulosa has good removal effect for N and P in two different eutrophic waters. Net rates for N removal were 54.909%,66.4097%, and the rates for P removal were 42.686%,61.2714%. Therefore, V. spinulosa can be used for the purification of eutrophic water. Compared to net rates for N and P removal in the eutrophic water, the rates for N and P removal with O. clecumbens and T. latifolia in the abnormal eutrophic water were more than 11.044%,10.8972% and7.11%,12.1073% respectively. O. clecumbens and T. latifolia have advantages in the purification of abnormal eutrophic water. C. demersum has good removal effect for N and P in the eutrophic water. Net rates for N and P removal were 43.995%,62.2336%.3. The removal effect for COD with V. spinulosa, I. aquatica and E. crassipes in the eutrophic water were better than this effect in the abnormal eutrophic water. Net rates for COD removal with V. spinulosa and I. aquatica in the eutrophic water were 3.333% and 1.52% higher than the rates in the abnormal eutrophic water respectively. The function of other four aquatic plants in the purification of abnormal eutrophic water was superior to that in the eutrophic water.4. V. spinulosa has good effect in restoration of DO, pH decreasing and promotion of transparency, and the values were 46.758%,0.27 and 32cm respectively. 5. The removal effects for N, P and COD of aquatic plants play especially important role in the purification of eutrophic water, especially submerged plants. V. spinulosa has good effect in decreasing the content of N, P and COD, restoration of DO, and promotion of transparency in two eutrophic waters. Therefore, in the research of the purification of two different eutrophic water, shall be given priority to use V. spinulosa.