【作者】 朱敏；

【导师】 王建； 王国祥；

【作者基本信息】 南京师范大学 ， 自然地理学， 2004， 硕士

【摘要】 凤眼莲是最早用于污水净化的植物之一，在藻型富营养化水体生态修复中有着重要的作用。以往对凤眼莲的研究主要集中在凤眼莲生长旺期对水质净化的作用，而就凤眼莲整个生长过程对污染物及水环境的影响研究尚不多，所以，往往根据直观的现象，认为凤眼莲衰亡腐烂会形成“二次污染”。究竟凤眼莲在什么时候、什么条件下会形成“二次污染”?“二次污染”的程度有多大?凤眼莲对污染水体的净化作用能够持续多久?这些问题尚需要进一步深入研究。本实验从初冬季节开始，模拟不同密度的凤眼莲在湖泊水体中的自然衰亡和腐解过程对水体和底泥的影响，通过与对照区对比分析，得出以下结论： （1） 初冬季节在富营养化水体中引种凤眼莲后，虽然气温较低，凤眼莲基本停止生长，但凤眼莲对富营养化水体的有机污染指标COD_Mn、营养盐指标TP、TN、NH₄⁺-N和生物指标叶绿素均有去除能力，去除能力的强弱与凤眼莲生物量的多少成正比；在初冬季节的净化能力没有在生长旺盛期强，放养100 kg的D3区对TP、TN、NH₄⁺-N、COD_Mn的净化率分别只有生长旺盛期的83.1％、25.7％、55.2％和21.3 （2） 凤眼莲开始衰亡至完全沉降前这一阶段，不同密度的凤眼莲对水体DO有影响，对照区D8（未放养凤眼莲）的DO始终大于投放风眼莲的试验区；出现对水体营养盐污染的时间与投放凤眼莲生物量有关，最早出现污染的是第61天在D3区的NH₄⁺-N指标，最晚出现污染的是第92大在D7区（放养25kg凤眼莲）的TP指标；因水体的自净作用，对水体COD_Mn没有明显的污染作用；这一阶段凤眼莲残体腐烂对水体叶绿素基本没有影响，主要是自然变化过程。 （3） 在凤眼莲残体完全沉降后，各试验区DO、COD_Mn、Chla及水体透明度的最恶值均出现在最热的7、8月份；这个阶段投放凤眼莲的试验区水体继续受营养盐污染，凤眼莲生物量越多，对水体TP、TN污染持续的时间越长，D3区比D7区分别长60天和87天。 （4） 凤眼莲残体完全沉降后，底泥营养盐浓度增加明显，营养盐上升量与凤眼莲放养量成正相关，投放100 kg的D3区底泥中的TP、TN、TOC增加最多，分别增加了31.78％、31.17％和52.17％，投放25 kg的D7区底泥中的TP、TN、TOC则分别增加了18.03％、17.25％、24.32％。这表明凤眼莲残体对沉积物有一定污染作用。更多还原

【Abstract】 Water hyacinth, Eichhonia Cassipes Solms, has been widely used in wastewater treatment. It plays an important role in remediation of phytoplankton-dominated eutrophic water. However, its application has been limited because it causes many ecological and environmental problems. Most research on the purification of water hyacinth was done during the vigorous growth period of water hyacinth, and it is very few that studying the effect on water environment and contaminants during the whole growth of water hyacinth. Accordingly, when water hyacinth began to decline and decay, they were considered as "secondary pollution". But when and what conditions do they come into being "secondary pollution"? How deep of the degree are they? How long can the purification of water quality persist? All these questions need to thorough research. The experiment began in early winter and simulated the effect of water hyacinth’s natural decline and decay of different density in a eutrophic water, the following conclusions were gotten:(1) After the water hyacinth was planted in eutrophic water in early winter, it can reduce the concentration of CODMn.TP, TN, NH4+-N and Chla although the temperature of water was low and its growth rate was very slow. But the capability of purification in early winter was weaker than that of in its vigorous growth, such as the capability of purification to the concentration of TP, TN, NH4+-N, CODMn of the experimental enclosure D3 in early winter, which planted 100 kg water hyacinth, was only 83.1 %, 25.7%, 55.2% and 21.3% of in its vigorous growths(2) During the period from the beginning of water hyacinth death to disappeared completely in water surface, the remains of water hyacinth can influence the dissolved oxygen (DO). The DO in the experimental enclosure D8 was higher than DO in other enclosures with remains of water hyacinth all the time. The time when the nutrients began to increase was related to the original biomass of water hyacinth in each enclosure. The NH4+-N was the earlist pollution and it happened in the sixty-first day in the experimental enclosure D3. The TP was the latest and it appeared in the ninety-second day. There wasn’t clear pollution to the CODMn and Chla because of natural purification.(3) After all the remains disappeared from water surface and deposited to the water bottom, the water quality become worse and worse day by day. During this time, the nutrients of water of experimental encolsure D3, D5, D7 kept increasing. The periods of TP and TN pollution in enclosure D3 were 60 days and 87 days longer than that of D7 respectively. The original biomasses were 100, 50, 25 kg in enclosure D3, D5, D7.(4) After all the remains deposited to bottom, the concentration of nutrients in sediments increased obviously. There was positive correlation between the degree of sediment-pollution and the original quantity of water hyacinth in each encosure. The TP, TN, TOC of the sediment in D3 increased 31.78%, 31.17% and 52.17% respectively, while these indexes increased 18.03%, 17.25% and 24.32% respectively in D7.更多还原