凤眼莲及底泥对富营养化水体反硝化脱氮特征的影响研究

利用改进的漂浮箱法，通过直接测定水体释放的N2O、N2，在模拟实验中研究种养及未种养漂浮植物凤眼莲条件下富营养化水体硝化、反硝化脱氮释放N2、N2O特征及其对消减水体氮的贡献。结果表明，种养或未种养凤眼莲的富营养化水体硝化、反硝化脱氮的产物以N2为主，硝化、反硝化脱氮释放N2O而脱除的氮仅占水体TN损失量的0．01％＋0．003％。在实验设定的水体富营养化条件下（NH4^＋ —N浓度6．0～7．2mg·L^-1、NO3^- -N浓度0．81～5．14mg·L^-1、TN浓度为8．9～12．07mg·L^-1），种养凤眼莲的富营养化水体（无底泥）以向大气界面累积释放N2形式损失的氮量（N2-N量，以N计）为（1609．1±303．4）-（2265．2±262．6）mg，占水体氮损失量的63．2％-17．0％，凤眼莲吸收的N仅占水体TN损失量的（23．7±3．1）％～（28．7±4．8）％，并不是净化水体氮的唯一途径。未种养凤眼莲的富营养化水体（无底泥）向大气界面累积释放N2形式损失的氮占整个水体N损失量的（40．7±8．6）％-（43．6±0．8）％，是富营养化水体自净脱氮的主要途径。施加底泥进一步促进了水体通过反硝化脱氮释放N2而损失的氮量。凤眼莲与底泥对促进反硝化脱氮过程具有良好的交互作用（P〈0．01）。种养凤眼莲的富营养化水体向大气界面释放N2的浓度显著（P〈0．05）高于相应处理下未种养凤眼莲的对照水体，说明凤眼莲可能对水体反硝化脱氮过程有促进作用。

Nitrogen Removal Via Denitrification from Eutrophic Water as Influenced by Eichhonia crassipes and Sediment

Nitrogen gas （N2） is believed to be the main gaseous product of nitrification and/or denitrification occurred in eutrophic water. Total removal of N2 and N2O from eutrophic water with or without cultivation of water hyacinth（Eichhonia crassipes ） was investigated using an improved floating-chamber method to directly measure N2 and N2O emission from water. Under the high concentrations of N （NH4^＋ -N：6.0 - 7.2 mg.L-1; NO3^- -N：0.81-5.14 mg·L-1; TN 8.9-12.07 mg.L-1）, growing E. crassipes without sediment removed（1 609.1±303.4）~（2 265.2±262.6）mg N from the water, accounting for （63.2±17.0）% of the total N loss from the water. However, only（23.7±3.1 ）%~（28.7±4.8）% of the total N loss was from N uptake by E. crassipes. In the treatments without E. Crassipes or sediment, N2 emission（689.0±29.2）-（ 1142.9± 17.5 ）rag N2-N] accounted for（40.7±8.6）%-（43.6±0.8 ）% of total N loss from the water. Applying sediment to the water further increased N2 emission via nitrification and/or denitrification. Interactions between E. crassipes and sediment were significant（P〈0.01 ）. In general, N2 produced in the water was significantly higher（P〈0.05 ） with than without E. crassipes. The findings suggest that cultivation of Eichhonia crassipes had a stimulation effect On denitrification process in eutrophic water.