Comparison of nitrogen and phosphorus purification ability of six aquatic macrophytes under low temperature in winter

Mean purification ability of nitrogen(N) and phosphorus(P) were investigated by using six aquatic macrophytes(Myriophyllum aquaticum,Hydrocotyle vulgaris,Iris ptectorum,Iris pseudacorus,Ceratophyllum demersum,Hydrilla verticillata) in the condition of static water.The results showed that:(1)For these six aquatic macrophytes,both Myriophyllum aquaticum and Hydrocotyle vulgaris showed relatively large increase in biomass;Iris ptectorum and Iris pseudacorus were able to keep growing at normal speed with the biomass increase;Ceratophyllum demersum barely showed growth while partial rot was found in Hydrilla verticillata.(2)Relatively significant differences in the purification rates of total nitrogen(TN) and total phosphorus(TP) were found for the six aquatic macrophytes.With the reference to the non-aquatic macrophytes,the effects of Myriophyllum aquaticum,Hydrocotyle vulgaris,Iris ptectorum,Iris pseudacorus,Ceratophyllum demersum,Hydrilla verticillata in speeding the purification process of TN were 45.7%,39.6%,18.7%,16.4%,6.1% and-4.1%,respectively,while for TP,the speeding rates of these six aquatic macrophytes were 31.1%,30.1%,16.7%,9.9%,3.3% and-2.0%,respectively.(3) Myriophyllum aquaticum and Hydrocotyle vulgaris could be chosen as the possible aquatic macrophytes for various biological projects under the circumstance of low temperature in winter.