Comparison of Nitrogen and Phosphorus Uptake and Water Purification Ability of Ten Aquatic Macrophytes

Ten aquatic macrophytes uptake of nitrogen(N)and phosphorus(P)and their water purification capacity were investigated in hy-drostatic conditions from middle February 2009 to middle June 2009,including Hydrocleys nymphoides,Jussiaea repens,Myriophyllum aquaticum,Hydrocotyle vulgaris,Oenanthe javanica,Pistia stratiotes,Eichhornia crassipes,Canna indica,Iris pseudacorus,Iris tectorum.Results showed that(1)the net accumulated biomass strongly changed from 109.9 g.m-2 to 1511.1 g.m-2 among different aquatic macro-phytes,with the highest biomass of Hydrocotyle vulgaris and the lowest of Jussiaea repens(;2)there was little difference in N and P concen-tration among different aquatic macrophytes,with the range of N and P contents 13.67~26.38 mg.g-1 and 1.16~3.50 mg.g-1,respectively(;3) there was greater difference in the water purification ability among thsee ten aquatic macrophytes,with the range of N and P removal efficien-cy 36.3%~91.8% and 23.2%~94.0%,respectively.The uptake of N and P and their accumulation in macrophytes were the main mechanism for the water purification,which accounted for 46.3%~77.0% and 54.3%~92.7% of the nitrogen and phosphorus removal efficiency.N and P removal efficiency in water body was significantly correlated with plant net accumulated biomass,but not with N and P concentration in macrophytes,thus N and P absorption instend of N and P concentration should be an important index for aquatic macrophytes choosing.