苦草对水-底泥-沉水植物系统中氮素迁移转化的影响

通过模拟水-底泥-沉水植物(苦草)系统,检测了苦草整个生命周期内总氮及各形态氮含量的变化,以反映N在该系统内的迁移转换.结果表明,在整个研究阶段,空白组和苦草组系统氮含量(水体+底泥+苦草中氮含量)均持续降低,但苦草组(实验始末)氮含量降低幅度明显高于空白组,其中苦草组系统中TN、NH4+-N、NO3--N含量分别减少了41.68%、81.96%、93.34%,分别比空白组提高了11.39%、31.90%、0.28%;苦草组底泥中TN、NH4+-N、NO3--N含量分别减少了43.45%、87.41%、96.50%,分别比空白组提高了13.78%、37.26%、1.68%.苦草的存在促进了底泥氮的释放,显著提升了底泥微生物活性及氮循环菌的数量,从而加快了系统内的氮素循环,并在其生命周期的不同阶段明显改变各形态氮的迁移及转化方式.2012年7~10月,苦草组系统总氮(TN)减少幅度最大,到10月份,水体中氮素含量达到最少.

Effect on nitrogen transfer and migration by Vallisneria natans (Lour.) Hara in water-sediment-submerged macrophytes system

The changes of nitrogen in water, sediment and submerged macrophytes (Vallisneria natans (Lour.) Hara) as well as its migration and transformation in the life cycle of V. natans were studied. The results indicated that the total nitrogen content was reducing continuously in V. natans and control treatments during the research stage, and the removing rate of total nitrogen in V. natans treatments was obviously higher than that in control treatments. The content of TN、NH4+-N、NO3--N in the water-sediment-submerged macrophytes system decreased by 41.68%, 81.96% , 93.34%, and the removal rates increased by 11.39%, 31.90, 0.28% than that in control treatment, respectively. In this system, the content of TN, NH4+-N, NO3--N in sediment decreased by 43.45%, 87.41%, 96.50%, and the removal rates are increased 13.78%, 37.26%, 1.68% than that in control treatment, respectively. V. natans contributed to nitrogen nutrients release in the sediment. The sediment microorganisms activity and the amount of nitrogen cycling bacteria were improved significantly. Therefore, the nitrogen cycle speed would be accelerated. The direction of transfer and transformation of nitrogen would be changed in the different stage of life cycle of V. natans. Compared with other stages, the nitrogen content in experiment group with V. natans decreased most during July to October of 2012. To October, the nitrogen content in water reached a minimum value.