【作者】 陶益；

【导师】 张锡辉；

【作者基本信息】 清华大学 ， 环境科学与工程， 2010， 博士

【摘要】 本论文选取蓝藻藻种铜绿微囊藻、绿藻藻种椭圆小球藻、普通小球藻、斜生栅藻等作为典型藻类,研究了不同藻密度条件下UV-C辐照对藻细胞生长的抑制效果,采用流式细胞术、调制荧光技术、实时荧光定量PCR技术等方法,确定抑制生长且膜损伤影响小的UV-C辐照剂量范围,通过测定藻细胞生理活性及光合作用的影响以揭示抑藻的动态机制,比较了所实验藻种对UV-C辐照的敏感性,现场调查深圳荔枝湖治理工程中组合工艺的控藻效果及局限性,提出UV-C辐照抑藻的应用思路。UV-C辐照能显著抑制铜绿微囊藻的生长。对于初始藻密度为105~107个·mL-1的铜绿微囊藻,采用50~200 mJ·cm-2 UV-C辐照,能够抑制藻细胞增长,抑制期为5~15 d。UV-C辐照的抑制效果与辐照剂量有关,与初始藻密度无关。20~50 mJ·cm-2 UV-C辐照后,超过80%的藻细胞保持细胞膜完整。100~200 mJ·cm-2 UV-C辐照后70~90%的细胞破裂。深入研究了UV-C辐照的抑藻机理,光合蛋白的编码基因转录过程首先受到抑制;其次水溶性色素容易受到损伤,影响光能捕获和传递过程;D1蛋白受到损伤,降低电子产率和传递速率,影响能量转化和电子传递过程。藻细胞能够应急启动修复机制,但不足以弥补损伤程度。当水溶性色素位点损伤加剧,光能捕获和传递过程进一步降低;D1蛋白损伤加剧,电子产率和传递速率迅速降低,影响ATP合成及CO2固定,细胞生长所需的能量和有机物供给不足,使藻细胞生长受到抑制。藻细胞代谢活性受到辐照影响,但其程度较光合作用受影响的程度低。藻细胞内活性氧物质得到产生和积累,形成氧化压力,也是藻细胞受到损伤的机制之一。UV-C辐照使椭圆小球藻、普通小球藻、斜生栅藻等增速变缓,但无致死影响。3种绿藻对UV-C辐照的敏感性显著低于铜绿微囊藻。传统组合工艺的控藻效果比较差,提出采用移动式UV-C辐照技术抑制藻类生长,实现藻类生物量的原位控制。更多还原

【Abstract】 This thesis explored the suppression effectiveness of typical algae growth under UV-C irradiation. Cyanobacteria Microcystis aeruginosa and three common freshwater green algae Chlorella ellipsoidea, Chlorella vulgaris, and Scenedesmus quadricanda were selected. The membrane integrity of UV-C irradiated algal cells were identified using flow cytometry to determine the UV-C irradiation dose range that can avoid extensive lysis as well as suppress algal growth. The physiological and photosynthetic activities in UV-C irradiated algal cells were investigated to probe into the mechanism of algal suppression effect. The sensitivities of the typical algae to UV-C irradiation were compared based on their responses on growth, membrane integrity, and pigment concentration. The effectiveness and limitation of the integrated engineering processes on algal control in the Lichee lake restoration project at Shenzhen were investigated and UV-C irradiation was proposed for in-situ algal control.The results indicated that UV-C irradiation at 50²00 mJ·cm-2 can effectively suppress M. aeruginosa growth for 5¹5 d in a dose-dependent manner for different initial cell densities settings. Over 80% of the cells exposed to UV-C irradiation at 20 and 50 mJ·cm^-2 remained intact. However, UV-C irradiation at 100 and 200 mJ·cm-2 induced severe cell disintegration in more than 70% of the irradiated cells.The results suggested that the mechanism of growth suppression includes sequenced damage/recovery procedures at cellular, biochemical, and genetical levels. UV-C irradiation suppressed the transcription process of the coding genes, disrupted the absorption and transportation of light energy by reducing aqueous pigments, affected energy transformation and electron transportation by attacking D1 protein and reducing electron transportation rate. The recovery processes of algal cell itself were immediately activated including accelerating D1 protein synthesis, shifting the genetic transcription levels, and increasing heat dissipation. However, these were insufficient to avoid further damage. Such damages on aqueous pigments and D1 protein may be magnified that resulted in further decrease on light absorption and electron transportation. Thus photosynthetic procedures including ATP synthesis and CO2 fixation were disrupted that inducing insufficient supply of both energy and organic materials. Therefore algal metabolic activities might be reduced and led to the growth suppression. The intracellular oxidative stress was enhanced as the increasingly production and accumulation of the reactive oxygen species. Related intracellular oxidative damage might be the sub-results of UV-C irradiation.It was found that neither significant suppression nor disintegration effects on green algae were obvious for UV-C irradiation at 20²00 mJ·cm-2 in this study. The non-toxic C. ellipsoidea, C. vulgaris, and S. quadricanda were less sensitive than M. aeruginosa to UV-C irradiation, which might suggest the potential application of UV-C irradiation on M. aeruginosa bloom control with a predictable low ecological risk.The conventional processes adopted at Lichee Lake were insufficient to control algal growth. The application of UV-C irradiation was proposed for in-situ suppression on algal blooming.更多还原