【作者】 李丽；

【导师】 杨扬；

【作者基本信息】 暨南大学 ， 环境科学， 2011， 硕士

【摘要】 湿地植物作为水生态系统的重要组成部分,具有重要的生态功能。近年来,植物修复技术因其造价低、效果好而越来越多地被运用于各种重污染水体的净化和修复。已有的研究结果表明,湿地植物对水质的净化作用,与植物的生长状况、根系发达程度、光合效率和根系泌氧等生理生态特性之间存在密切相关。但植物的生理生态特性如何影响植物的净化作用,以及哪些因子对植物净化能力有重要影响,尚不清楚。因此,本研究主要从植物生理生态学角度探讨湿地植物对污染水体的适应机制及对水质净化的作用,以期为植物修复技术在水污染处理中的应用提供更多理论依据。本研究通过室内水培试验,以不同生长特性和不同根系结构的11种湿地植物为对象(包括根茎型挺水植物黄菖蒲、美人蕉和梭鱼草,须根型挺水植物风车草、香根草和象草,以及木榄、桐花树、老鼠勒、秋茄和无瓣海桑等红树植物),以氮、磷和有机物为污染负荷,通过对植物的一些生理生态特性进行测定和分析,得到如下主要结论：1.脯氨酸可作为指示植物抗逆性强弱的一项生化指标。本研究11种湿地植物的脯氨酸积累倍数显示,污染负荷对红树湿地植物产生的胁迫大于挺水湿地植物,5种红树湿地植物中的无瓣海桑和木榄的抗逆性相对较强,6种挺水湿地植物则具有相似的抗逆能力。而污染负荷对湿地植物生长的抑制主要表现在对茎叶生物量的抑制,11种湿地植物的相对生长速率(RGR)大小排序为：美人蕉≈香根草≈黄菖蒲>象草≈风车草>梭鱼草>无瓣海桑≈老鼠勒≈秋茄>桐花树≈木榄。2.湿地植物在生长过程中大量吸收可溶解态的氮、磷等营养元素,N和P吸收量范围为：1.05～146.55 mg/m2·d和0.34～13.91 mg/m2·d,不同植物间氮、磷吸收量的差异主要来自生物量的差异。11种湿地植物水上茎叶部分生物量均占总生物量的70%以上,部分挺水湿地植物的比例甚至达90%以上,呈现良好的生物量分布。3.根孔隙度与脯氨酸积累倍数呈极显著正相关关系(p<0.01),表明根孔隙度一定程度上也可作为植物抗逆性指标。其中红树植物根孔隙度最大,为17.70～43.79%；其次是根茎型湿地植物,10.75～32.49%；须根型湿地植物孔隙度最小,仅为9.95～15.43%。而6种挺水湿地植物根系泌氧率与孔隙度表现出极显著的线性相关关系(p<0.01),即孔隙度大的根茎型植物泌氧率高,为84.69～205.25μmol O2d-1g-1DWroot;而孔隙度较小的须根型植物泌氧率较低,为12.50～111.23μmol O2d-1g-1DWroot。从而推测孔隙度最大的红树植物具有更高的泌氧率。湿地植物总泌氧量越大,越有利于根系好氧微生物的作用以及植物根系对可溶解态氮、磷的吸收。4.PSⅡ最大光化学量子产量(Fv/Fm),反映了植物的潜在最大光合能力,正常生理状态下一般认为在0.8-0.85之间。在本研究试验期间,黄菖蒲、美人蕉、梭鱼草、风车草和香根草的Fv/Fm值维持在正常生理水平,表明该5种挺水植物对污染负荷的耐受能力。而5种红树植物的Fv/Fm值呈现先下降后上升的趋势,表明随着试验时间的延长,红树植物表现出对污染负荷条件的适应。PSⅡ的实际量子产量(Yield)反映了植物的实际光合效率。试验后期,黄菖蒲、美人蕉、梭鱼草和风车草的Yield值最高,表明具有最高的光合效率,其次是5种红树湿地植物,象草和香根草Yield值最低。光合效率越高的植物,其通过光合作用将氧传输至水下根部,有利于植物根系向更深的缺氧区域深入。因此,光合效率较高的黄菖蒲、美人蕉和梭鱼草,其根系可向下分布至15～20 cm的区域,香根草、风车草和5种红树植物则分布至10～15 cm区域,象草根系仅分布在0～6 cm区域。而根系分布范围越大,越有利于硝态氮和可生化有机物的好氧和厌氧的生物降解作用同时进行。5.对污染物去除效率的影响因子进行逐步回归分析,进一步证实：湿地植物可通过抗氧化酶系统的作用(脯氨酸积累)适应污染胁迫条件,并在生长过程中吸收可溶性氮、磷于茎叶部分积累,对氮、磷去除有重要贡献；植物根系生物量和总泌氧量对氨氮的硝化起重要影响；而光合作用则主要影响湿地植物对硝氮和可生化有机物的降解。6.综合评价11种湿地植物在本研究两个污染负荷条件下的表现,结果显示11种湿地植物在低污染负荷条件下的表现均优于高污染负荷条件,而6种挺水植物要普遍优于5种红树植物。其中美人蕉低负荷条件下的表现最佳；而象草高负荷条件下的表现最差。7.利用填料和湿地植物构建强化型生态浮床,对南方重污染城市河流进行原位修复。其中,湿地植物RGR排序为：美人蕉>再力花≈风车草>梭鱼草≈黄菖蒲。植物生长过程中吸收的氮、磷量分别为136.99～356.16 mg/m2·d和21.37～63.01 mg/m2·d.植物具有良好的根系分布,达到20 cm以下区域。而通过质量恒算法获得植物氧输送率为35.85-57.08 g O2·m-2·d-1,表明湿地植物对浮床系统净化效果的重要作用。综上所述,根系泌氧和植物体内的抗氧化酶系统一起组合成湿地植物对污染负荷的适应机制；而在水质净化过程中,发达的植物根系生物量保证了植物对可溶性氮、磷的吸收作用,根系泌氧促进了污染物的好氧降解,而光合作用主要影响硝氮和可生化有机物的降解。本研究可为植物修复技术应用需求提供参考。更多还原

【Abstract】 As an important component of the aquatic ecosystem, wetland plants have important ecological functions, In recent years, phytoremediation technology is increasingly being used in the purification and restoration of heavily polluted water because of its low cost and high efficiency. Previous studies have showed significant corelation between water purification ability and physioecological characteristics, such as growth characteristics, root features, photo synthetic efficiency, root oxygen loss, and so on. But it remains unclear how these factors effect on water purification, and which one plays the leading role. Therefore, this study was carried out to investigate the adaptation mechanism and roles of wetland plants in wastewater purification from the angle of physiological ecology. The aim was to provide theory basis for the application of phytoremediation technology in wastewater treatment.We have drawn conclusions as follows after hydroponic experiments under greenhouse conditions and filed application, which were related to the activities for the growing features, physioecological characteristics and decontamination efficiency of 11 species of wetland plants. These plants were three kinds of rhizomatic root plants (Canna indica, Iris pseudacorus and Pontederia cordata), three kinds of fibril root plants (Cyperus alterniflius, Vetiveria zizanioiaes and Pennisetum americanum) and five mangroves (Sonneratia apetala, Acanthus ilicifolius, Kandelia candel, Aegiceras corniculatum and Bruguiera gymnorrhiza).Firstly, proline can be used as an indicator to indicate the tolerance ability of plants. The change of poline concentration in these 11 species of plants have showed that, the stress to wetland plants grown in high concentration sewage was higher than that in low concentration, while the stress to mangroves was higher than emerged plants. This stress was found mainly to reduce the above-water biomass of wetland plants. The relative growth rates (RGR) order of the 11 species of wetland plants was C. indica≈V. zizanioiaes≈I. pseudacorus> P. americanum≈C. alterniflius> P. cordata> S. apetala≈A. ilicifolius≈K. candel> A. corniculatum≈B. gymnorrhiza.Secondly, plants can absorb soluble nitrogen and phosphorus during growth process. The total gross absorption for N and P was estimated to be 1.05 to 146.55 and 0.34 to 13.91 mg/m2·d. The difference of N and P accumulation by plants mainly came from the biomass differences. The plants have showed good biomass distribution, the stem and leaf biomass accout for over 70% of the total biomass.Thirdly, there was significant positive correlation between root porosity and proline accumulation (p< 0.01). The root porosity also can be used as a tolerance index of plants in a way. Of all these plants, mangroves stood out for its highest root porosity (17.70 to 43.79%), followed by rhizomatic root plants (10.75 to 32.49%). The lowest one was the fibril root plants, only 9.95 to 15.43%. There was significant positive correlation between the root of radial oxygen loss (ROL) rate and porosity of 6 species of emerged plants (p< 0.01), ie the ROL rate of high root porosity (rhizomatic root plants) was higher than the low one (fibril root plants), which were 84.69 to 205.25 and 12.5 to 111.23μmolO2d-1g-1DWroot, respectively. The larger the total ROL amount, the more active the aerobic rhizospherebacterial, which was also useful for the root to absorb more soluble nitrogen and phosphorus.Fourthly, PSⅡmaximum photochemical efficiency (Fv/Fm) value, reflected the potential maximal photosynthetic capacity of plants. For C. indica, I. pseudacorus, P. cordata, C. alterniflius and V. zizanioiaes, their Fv/Fm values have maintained between 0.80 to 0.85, showing the normal physiological condition. The Fv/Fm value of mangroves decreased firstly and then increased, it suggested the adaptability of pollutants. The Yield value reflected the actual photosynthetic efficiency, so the higher the Yield value, the higher the photosynthetic efficiency. Of all these plants,I. pseudacorus, C. indica, P. cordata and C. alterniflius stood out for their highest photosynthetic efficiency, and then were five mangroves; the lowest were V. zizanioiaes and P. americanum. For the high photosynthetic efficiency plant, it was much easier for the above-water part of the plant to transport oxygen down to the root system to help the root to reach deeper anoxic area. Therefore, for I. pseudacorus, C. indica and P. cordata, their roots can reach upper 15 to 20 cm layer, and V. zizanioiaes, C. alterniflius and five kinds of mangroves, can reach upper 10 to 15 cm layer, but the root of P. americanum was below 6 cm. In addition, as the roots distribution deepened, the aerobic and anaerobic biodegradation of nitrate nitrogen and biochemical organic compounds could take place at the same time and show better performance.Fifthly, Stepwise regression analysis showed that:antioxidant enzyme in plant tissues was a very efficient and important mechanism for tolerance and adaptability of wastewater by wetland plants. Nitrogen and phosphorus accumulation in stem and leaf have made an important contribution to nitrogen and phosphorus removal. Root biomass and the total ROL amount had important effect on nitrification, and photosynthesis plays an important role in degradation of nitrate nitrogen and biochemical organic compounds.Sixthly, Principal component analysis (PCA) showed that:(a) the performance of these 11 species of wetland plants was better in low concentration sewage than in high concentration; (b) the 6 species of emerged plants was better than the 5 mangroves in low concentration sewage, of which C. indica have the highest photosynthetic efficiency, the largest biomass and the deepest root distribution. And the P. americanum performed the worst in high concentration sewage.Seventhly, we have been trying to establish an enhanced ecological floating bed system by using fillers and wetland plants, hoping to restore the water quality of the heavily polluted south urban tidal rivers in situ. As a result of our observation and monitoring, the RGR order of the wetland plants was C. indica> Thalia dealbata≈C. alterniflius> P. cordata≈I. pseudacorus. N and P were removed by mowing the above water-part of the plants, the total gross was estimated to be 136.99 to 356.16 and 21.37 to 63.01 mg/m2·d, respectively. Wetland plants showed good root distribution that can reach upper 20 cm layer. Finally, the oxygen-transfer rates was estimated, which was 35.85 to 57.08 gO2·m-2·d-1. Wetland plants showed the advantages of improving the treatment effect of pollutants.In conclusion, antioxidant enzymes in plant tissues combined ROL from roots are very efficient and important mechanisms for tolerance and adaptability of pollutants (N, P and organic compounds) by wetland plants. Well developed root system keeps the nitrogen and phosphorus absorption, root oxygen loss improves the aerobic biodegradation, and photosynthesis plays an important role in degradation of nitrate nitrogen and biochemical organic compounds. This study can provide reference for application of phytoremediation technology.更多还原