【作者】 廖兴盛；

【导师】 赵开弘；

【作者基本信息】 华中科技大学 ， 环境工程， 2009， 博士

【摘要】 水体中暴发的蓝藻“水华”，不仅使供水管道发生阻塞，而且还会使水体产生异味和向水体释放出毒素，对水环境造成了严重危害。为了有效保护水环境，防止蓝藻“水华”危害，对蓝藻“水华”实施有效治理是十分必要。当前，在众多蓝藻“水华”防治技术中，因成本较高、防治后易于再次生长和产生二次污染等而收效甚微，研究能够克服以上技术的不足，能有效防治蓝藻“水华”的新技术是十分必要。灭菌紫外线（UV-C）能杀死各种细菌和病毒，当被用于杀灭蓝藻细胞时，因蓝藻细胞的保护作用，很难对蓝藻细胞产生损伤。因此，对于抑制疯长的蓝藻，灭菌紫外线面临巨大的挑战。纳米TiO₂，具有对自然环境无毒、化学性能稳定、使用成本低廉和光催化活性高的优点。因而，利用UV-C光催化纳米TiO₂作用于蓝藻细胞，可以取得比UV-C单独作用时更有效的细胞损伤。本课题选用蓝藻“水华”中常见的鱼腥藻7120和铜绿微囊藻为实验蓝藻，以UV-C为催化光源和纳米TiO₂为催化剂，发生UV-C光催化纳米TiO₂反应，实现对蓝藻“水华”的模拟防治。研究结果为：首先，建立了UV-C光催化纳米TiO₂抑制蓝藻生长实验工艺，测定了工艺的反应参数，研究了对蓝藻生长影响的效果，通过鱼腥藻7120生理学参数测定，发现在蓝藻藻液中辐照光强约为0．10 mW／cm²、纳米TiO₂浓度为100 mg/L、反应温度为30℃和溶解氧浓度为9．0 mgO₂／L的条件下，反应60 min后，实验工艺能够有效阻止蓝藻生长。其次，对纳米TiO₂进行了改性，通过不同金属离子掺杂物对鱼腥藻7120叶绿素a浓度的变化，发现掺杂Ag⁺纳米TiO₂使鱼腥藻7120中叶绿素a浓度的下降更快。再次，研究了UV-C光催化Ag-TiO₂对实验蓝藻生长的影响，通过对蓝藻的细胞数目、叶绿素a浓度、藻蓝蛋白浓度、光合放氧速率、细胞形态结构、脂质过氧化、抗氧化性酶活性和双链DNA断裂进行测定，在分别与UV-C单独处理和UV-C光催化纳米TiO₂处理比较后，发现UV-C光催化掺杂Ag⁺纳米TiO₂更容易使蓝藻细胞受到活性氧化物作用，在蓝藻细胞膜产生过氧化反应，最终出现了蓝藻细胞壁发生破裂、蓝藻细胞器发生破损和蓝藻细胞生存能力完全丧失的结果；同时，在UV-C光催化掺杂5％Ag⁺纳米TiO₂反应中，因活性氧化物的作用，使蓝藻细胞膜遭受了更严重地损坏。最后，利用UV-C光催化掺杂Ag⁺纳米TiO₂获得的实验结果，设计适合于水体流域蓝藻“水华”治理的装置，并对设计装置的预期应用进行了分析。可以看出，本课题利用掺杂Ag⁺纳米TiO₂治理富营养化水体中过度生长的蓝藻，为一种有效的蓝藻“水华”治理技术。更多还原

【Abstract】 Cyanobacterial blooms are of concern in relation to waterbodies because of their abilityto result in filter-clogging, disagreeable tastes and odors, toxins generation, whichtremendously damage to aquatic environment. To protect effectively the aquaticenvironment from the damage of the cyanobacterial overgrowth, it is necessary to counteractcyanobacterial blooms in waterbodies. However, various methods have been used todiscourage cyanobacterial overgrowth in waterbodies at present, and almost all of those wereproved to be cost-consuming, inefficient or injurant-producing. Thus, new methods areneeded to prevent cyanobacteria from fast and excessive growth in the water sourceseffectively.The ability of ultraviolet light with a wavelength of 253.7 nm （UV-C） can kill variousbacteria and virus. However, the cells of cyanobacteria are more resistant to damage thanthose of bacteria and virus. Thus, it poses a greater challenge to the control of cyanobacterialovergrowth.Advantages of nanocrystalline TiO₂ in natural surroundings include its non-toxic nature,chemical stability, low cost, and high photoactivity. What exciting is that the UV-Cphotocatalysis by nanocrystalline TiO₂ may be more effective method to damage the cells ofcyanobacteria than that of UV-C irradiation alone.In this study, the capacity of the nanocrystalline TiO₂ in combination with UV-C lightto restrain cyanobacterial growth in laboratory scale was investigated with Anabaena sp.PCC 7120 and Microcystis aeruginosa as test species. The results lead to the followingconclusions: firstly, the experimental process of UV-C photocatalysis with nanocrystallineTiO₂ was investigated for several possible factors influenced the photocatalytic activities,and the effects of cyanobacterial growth by UV-C photocatalysis with nanocrystalline TiO₂were studied. The physiological parameter of Anabaena sp. PCC 7120 has been measured,and the results indicate that UV-C photocatalysis at radiation light intensity about 0.10mW/cm², nanocrystalline TiO₂ concentration 100 mg/l, the temperature 30℃, the dissolvedoxygen concentration 9.0 mgO₂.1^-1 for 60 min, could effectively inhibit the cells growth ofAnabaena sp. PCC 7120. Secondly, the improvement of photocatalytic activity by dopingthe certain metal ions in nanocrystalline TiO₂ under the optimal reaction condition wasinvestigated with Anabaena sp. PCC 7120, and the result indicate that the doped nanocrystalline TiO₂ with silver ions （Ag-doped TiO₂） could effectively reduce theChlorophyll a concentration of Anabaena sp. PCC 7120. Thirdly, the capacity of theAg-doped TiO₂ photocatalyst in combination with UV-C light to restrain cyanobacterialgrowth was investigated with Anabaena sp. PCC 7120 and Microcystis aeruginosa. The cellamount, chlorophyll a concentration, phycocyanin concentration, oxygen evolution rate,cellular morphologic structure, lipid peroxidation, antioxidant enzyme activities and dsDNAbreakage of test cyanobacteria were measured. Compared with the UV-C irradiation aloneand the UV-C photocatalysis by nanocrystalline TiO₂, the results showed that the testcyanobacteria with UV-C photocatalysis by Ag-doped TiO₂ yielded more effects of reactiveoxygen species, promoted peroxidation of cyanobacterial cell membrane and ultimatelycaused the damage of the cell wall, the losses of the cell organelle and viability. The 5atom% Ag-doped TiO₂ photocatalysis could damage more seriously the membranes ofcyanobacterial cells than the 1 atom% Ag-doped TiO₂, TiO₂ photocatalysis and UV-Cirradiation alone, which could be ascribed to the oxidation of the cell membranes caused byROS. Finally, according to the experimental data with UV-C photocatalysis by Ag-dopedTiO₂, the photocatalytic reactor was designed for preventing cyanobacteria from growth inthe water sources, and was discussed for applying in future.In this study, it has been found that nanocrystalline TiO₂ doped with Ag ion has thepotential to be used as an effective means for controlling cyanobaeterial overgrowth ineutrophic waterbodies。更多还原