苦草对不同浓度氮净化效果及其形态转化规律

为研究不同营养程度下水生植物对污染物的净化效果,选择长江中下游河流和湖泊水体中典型沉水植物苦草作为研究对象,在2006-09-07～2006-09-22期间开展了7种氮浓度条件下,苦草对水体氮的净化效应及氮在植物体内累积分布规律研究,并分析了水体中氮形态的转化特征.结果表明,试验期内苦草在氮浓度低于60.0 mg/L范围内表现为对水体中氮较强的净化作用,且对总氮的净化效果具有相似的规律性.但是当水体氮浓度大于80.0 mg/L时,苦草对水体氮净化的贡献无明显的规律性.氮在植物体内的累积与水体中氮浓度相关,但其在地下部和地上部的分配规律与浓度的差异无关.水体中氮的形态转换与总氮浓度相关,水中氮浓度低于20.0 mg/L时,氨氮浓度迅速降低,但随着氮浓度的增加,氨氮所占比例明显增大,表明苦草对不同氮浓度条件氮净化具有明显的差异和影响.

Purification Effects on Nitrogen Under Different Concentration and Nitrogen Conformation Transform Principles by Vallisneria spiraslis L.

Wet vegetation performed different physiological actions under different pollution loads, thus inducing different purification effects on pollutants. Since water of various rivers, lakes and ponds are polluted at different extents and purification levels currently in China, a typical submerged vegetation, Vallisneria spiraslis L. is selected to study the purification effects on total nitrogen(TN) under different purification levels, which is widely distributed in rivers and lakes of Yangtz middle and down stream. The targets of this paper are to determine the nitrogen degradation impacts of Vallisneria spiraslis L., and nitrogen accumulation and distribution in leaf and root rules, and inorganic nitrogen conformation transformation characters under 7 nitrogen loads during 7 to 22 Sept., 2006. The 7 nitrogen loads are 1.0 mg/L, 5.0 mg/L, 10.0 mg/L, 20.0 mg/L, 40.0 mg/L, 60.0 mg/L and 80.0 mg/L. The experiment data show that Vallisneria spiraslis L. have significant effects on nitrogen purification while the TN concentration equal to and less than 60 mg/L, and the contribution principles of vegetation are similar among the 6 loads. Whereas, when the TN load bigger than 80.0 mg/L, Vallisneria spiraslis L. have no obvious contribution on nitrogen purification. Meanwhile, the nitrogen accumulation principles in the leaf and root of Vallisneria spiraslis L. is interrelated to the TN load. However, its distribution ratio in leaf to root is unrelated with TN load. Furthermore, the conformation of inorganic nitrogen transform characters changed with the TN load increasing. It is concluded that ammonia concentration decreased rapidly while the nitrogen load less than 20.0 mg/L, and the ammonia concentration ratio in the inorganic nitrogen increased remarkably with the nitrogen load increasing. Results indicate Vallisneria spiraslis L. have different purification contribution extents which can be benefit for nitrogen removal in different eutrophicated water and wet vegetation restoration.