不同水生植物的除氮效率及对生物脱氮过程的调节作用

摘要

Eutrophication of water bodies has become a worldwide problem in recent years.So far,little has been reported on differences between types of aquatic plants in nitrogen (N) removal efficiency and function of controlling bio-denitrification processes,and variation of the function with growth stage of the plants.This will put us at a disadvantage when it comes to choose appropriate plant species and to further improve efficiency of the phytoremediation technology.With regard to this situation,an experiment was carried out to have four different types of aquatic plants (Eichhornia crassipes,Pistia stratiotes,Trapa bicornis,Hydrilla verticillata) to construct separately four microcosms for treating eutrophied water in an attempt to explore their N enrichment capacities,N removal efficiencies and functions of controlling bio-denitrification processes at different plant growth stages,i.e.initial growth period (June to July),rapid growth period (July to August) and slow growth period (September).Results show that the four types of aquatic plants differed significantly in NH4+-N,NO3--N and TN removal efficiency.The two types of floating plants,E.crassipes and P.stratiotes,were the highest in N removal efficiency and N enrichment capacity at all the growth stages with TN removal rate reaching (99.67±0.27)％ at the initial growth stage,(96.26±0.88)％ at the rapid growth stage and (63.86±3.77)％ at the slow growth stage,while the type of submerged plant,H.verticillata,was the lowest in N removal efficiency.Among the three growth stages,the rapid growth stage witnessed the highest N removal efficiency for all the types of plants,and was followed by the initial growth stage.In terms of N enrichment capability,the four types of aquatic plants displayed an order of E.crassipes＞P.stratiotes＞Trapa bicornis＞Hydrilla verticillata.However,the type of submerged plants released significantly more N2 and N2 O through bio-denitrification than all the others and so was its total gas release.The present study reveals that the aquatic plants differ in efficiency,pathway and mechanisms of N removal in eutrophied water with type and growth stage of the plants.It is,therefore,expected that all the findings in this experiment could provide some useful information on how to choose appropriate aquatic plants and improve efficiency of the phytoremediation technology in treating eutrophied water.%选取漂浮植物凤眼莲(Eichhornia crassipes)和大藻(Pistia stratiotes)、浮叶植物乌菱(Trapa bicornis)和沉水植物轮叶黑藻(Hydrilla verticillata)4种不同类型水生植物为供试植物,构建富营养化水体净化系统,在植物生长初期(6-7月)、快速生长期(7-8月)和缓慢生长期(9月)研究其吸收富集氮的能力、去除水体中氮的效率及对水体生物脱氮过程的影响.结果表明,4种水生植物去除水体氨氮、硝态氮、总氮的效率有所差异,凤眼莲、大藻在3个生长阶段对上覆水中各种形态氮的去除效率均较高,对氮的富集能力也较强,轮叶黑藻去除水体中氮的效率最低.快速生长期各类植物净化水体氮的速率最快,其次是生长初期.4种植物体内富集氮能力从大到小依次为凤眼莲、大藻、乌菱和轮叶黑藻,种植沉水植物的水体生物脱氮气体N2和N2O的释放通量以及气体释放总量明显高于其他类型水生植物.