【作者】 郑宾国；

【导师】 郑正；

【作者基本信息】 南京大学 ， 环境工程， 2012， 博士

【摘要】 水体富营养化,导致国内外众多湖库蓝藻生长泛滥,对饮用水安全造成了严重威胁。为防止蓝藻“水华”危害,必须采取有效措施对其实施治理。但现有的蓝藻“水华”防治技术,存在防治不彻底及易产生二次污染等问题。因此,研究能够克服以上技术的不足,能有效防治蓝藻“水华”的新技术迫在眉睫。γ-射线辐照和介质阻挡放电在作用过程中能产生活性很强的自由基,将水中许多有机污染物完全降解和矿化。作为高级氧化技术,与常规污染处理技术相比,γ-射线辐照和介质阻挡放电在常温常压下进行,工艺简单,效率高、无二次污染,适用于常规技术难以处理的环境污染物。本课题对γ-射线辐照抑制“水华”优势藻—铜绿微囊藻和鱼腥藻生长的情况进行了研究；分析了γ-射线辐照对铜绿微囊藻和鱼腥藻细胞内叶绿素a(Chl-a)、类胡萝卜素(Cartenoid)、藻蓝蛋白(PC)、总可溶性蛋白(TSP)和超氧化歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)等酶活及丙二醛(MDA)的影响；对比分析了γ-射线辐照处理前后铜绿微囊藻和鱼腥藻细胞表面及内部结构的变化,找出了辐照抑制两种蓝藻生长的机理；考察了γ-射线辐照和介质阻挡放电两种辐照手段对自然水体中“水华”蓝藻的去除,为辐照技术除藻的实际应用奠定理论基础；根据蓝藻的生理特性,研究γ-射线辐照对太湖越冬蓝藻复苏的抑制,为蓝藻“水华”的防治提供一个新思路。取得的主要研究结果为：(1)初始叶绿素a浓度为5.62mg/L的铜绿微囊藻悬浮液,经剂量9kGy的Y-射线辐照处理后,培养5d,悬浮液中Chl-a含量仅为对照样的2%,相当于98%铜绿微囊藻细胞被去除。酸性环境有利于γ-射线辐照对铜绿微囊藻的抑制。Y-射线辐照产生的.OH和H202对铜绿微囊藻细胞的生长抑制起主要作用。铜绿微囊藻细胞经γ-射线处理后,细胞内光合色素和蛋白含量随辐照剂量增加而降低,细胞内MDA含量逐步增加,说明细胞膜质已被氧化。γ-射线辐照处理后,铜绿微囊藻细胞内SOD、POD和CAT酶活性随辐照剂量增加是先增加后降低,辐照剂量达到9kGy时,藻细胞内活性酶系统几乎完全被损伤。藻细胞SEM和TEM图表明,辐照处理后铜绿微囊藻细胞萎缩,细胞内类囊体逐渐溶解和消失,降低了蓝藻细胞色素的光能捕获和传递能力,影响了细胞内蛋白电子产率和传递速率。最终,蓝藻细胞内能量转化和电子传递过程终止,细胞生长所需的能量和有机物供给不足,代谢活性降低,其生长受到抑制。(2)初始Chl-a浓度为5.62mg/L的鱼腥藻,经剂量11kGy的γ-射线辐照处理后培养5d,悬浮液中Chl-a含量为对照样的1.3%,相当于98.7%鱼腥藻被去除。酸性环境有利于γ-射线辐照对鱼腥藻的抑制。11kGy的γ-射线辐照处理后,鱼腥藻细胞内光合色素和蛋白含量几乎降低为零。鱼腥藻细胞内SOD、POD和CAT活性随辐照剂量的增加是先增加后降低,细胞内MDA含量随辐照剂量增加而逐步增加。通过SEM和TEM分析,发现经11kGy的γ-射线辐照处理后鱼腥藻大部分藻丝断裂,藻细胞严重萎缩,细胞内类囊体溶解消失,细胞内部生理功能受到不可逆损伤,以致藻细胞死亡。(3)γ-射线辐照能有效去除太湖水体中的“水华”蓝藻。初始Chl-a浓度为12.38mg/L的太湖“水华”蓝藻,经剂量10kGy的γ-射线辐照处理后培养5d,悬浮液中Chl-a含量为0.56mg/L,与对照样相比,相当于95.5%“水华”蓝藻被去除。γ-射线辐照处理后蓝藻细胞内Cartenoid、PC和TSP含量显著降低。随辐照剂量增加,蓝藻细胞内SOD和POD酶活性先增加后降低。辐照剂量越高,细胞内MDA含量越高,蓝藻细胞被氧化的程度越深。(4)介质阻挡放电也能有效去除太湖“水华”蓝藻。放电功率、放电时间、空气流速对去除效率均有影响。放电功率越高,放电时间越长,空气流速越大,蓝藻去除率越高。放电功率100W,放电时间18min,空气流速1.0L/min条件下,初始Chl-a浓度为9.58mg/L的藻液,经放电处理后培养4d,悬浮液中Chl-a浓度为对照样的12.2%,即蓝藻去除率达到了87.8%。放电处理后,蓝藻细胞内Cartenoid、PC、SOD、POD和MDA发生显著变化。(5)γ-射线辐照能有效抑制太湖越冬藻类的复苏,辐照剂量越大,抑制效果越好。太湖原水经5kGy的γ-射线辐照处理后培养40d,其Chl-a、Chl-b和PC含量仅为对照样的8.66%、16.8%和17.2%,太湖原水中越冬藻类的复苏受到了较大抑制。太湖底泥原样经剂量13kGy的Y-射线辐照处理后,采用BG11培养基培养60d,培养液中Chl-a、Chl-b和PC含量仅为对照样的18.8%、14.8%和20.5%,说明γ-射线对底泥中越冬藻类复苏有一定抑制。更多还原

【Abstract】 The eutrophication of natural water in lakes and drinking water reservoirs has led to an incease in the incidence of blue-green algae. The presence and excessive growth of algae in water poses a significant risk to drinking water treatment. To minimize the threat posed by algae, they have been removed from water by various methods. However, the existing methods are proved to be inefficient or secondary environmental pollution. Thus, new methods are needed to prevent algae from fast and excessive growth in the water sources effectively.As advanced oxidation technologies, gamma-ray irradiation and dielectric barrier discharge have been widely used in environmental protection field. The two technologies have the advantages of easy operation (room temperature and pressure) as well as high availability and no secondary pollution. They are appropriate to remove the environmental pollutants which are difficult to treat by conventional techniques.This thesis explored the suppression effectiveness of typical bloom algae growth under gamma-ray irradiation. Cyanobacteria microcystis aeruginosa and anabaena sp. were selected. The effects of gamma-ray irradiation on chlorophyll, carotenoid, phycocyanin and several antioxidative enzymes (SOD, POD and CAT) were discussed. The changes of surface and cellular ultrastructure in microcystis aeruginosa and anabaena sp. cells befor and after gamma-ray treatment were investigated to probe into the mechanism of algal suppression effect. Meanwhile, the removals of cyanobacteria in natural water by gamma-ray irradiation and dielectric barrier discharge were also discussed. The research results would provide the theoretical basis for the application of this technology. According to the physiological characteristics of cyanobacteria, the inhibition of overwintering cyanobacteria recovery in Lake Taihu by gamma-ray irradiation was also discussed, which provide us a new approach to the control of cyanobacterial bloom. The main results are showed as follows:(1) It was found that the chlorophyll a concentration of microcystis aeruginosa (the initial concentration of chl-a was5.62mg/L) suspensions decreased as the dose increased at five days after gamma irradiation, and the removal efficiency of chlorophyll a was98%when a dose of9kGy was administered. The solution pH influenced the removal of microcystis aeruginosa, with a higher removal efficiency being observed under acidic conditions than in neutral or alkaline conditions. The OH and H2O2derived from the irradiated water play an important role in microcystis aeruginosa removal. Gamma irradiation had an adverse effect on photosynthetic pigments in microcystis aeruginosa cells. Specifically, the levels of Carotenoid and phycocyanin in microcystis aeruginosa cells were reduced considerably in response to increasing doses of radiation. The gradually increased MDA in irradiated microcystis aeruginosa cells following lipid peroxidation indicated oxidative stress in the cells. During oxidative stress, active oxygen species (AOS) trigger the activity of several antioxidative enzymes (SOD, POD and CAT). Relatively low gamma irradiation doses enhanced the activity of antioxidative enzyme. However, high doses of gamma irradiation reduced the activity of antioxidative enzyme in microcystis aeruginosa cells. Based on the SEM and TEM images, the thylakoid in microcystis aeruginosa cell was lysised after gamma-ray irradiation treatment, which disrupted the absorption and transportation of light energy, affected energy transformation and electron transportation, even terminated these process. That induced insufficient supply of both energy and organic materials in microcystis aeruginosa cells. Therefore algal metabolic activities might be reduced and led to the growth suppression.(2) The chlorophyll a concentration of anabaena sp.(the initial chl-a concentration was5.62mg/L) suspensions decreased as the dose increased at five days after gamma irradiation, and the removal efficiency of chlorophyll a was98.7%when a dose of11kGy was selected. Gamma irradiation had an adverse effect on photosynthetic pigment and protein system in anabaena sp. cells. The activity of several antioxidative enzymes (SOD, POD and CAT) increased with relatively low gamma irradiation doses. However, the activity of these enzymes significantly decreased with relatively high gamma irradiation doses. The concentration of MDA increased with the increase of irradiation dose. As shown in the SEM and TEM images, some irradiated anabaena sp. cells atrophied, and the thylakoid lysised. So, the normal physiological function of cell was damaged.(3) The bloom cyanobacteria in Taihu Lake could be effectively removed by gamma-ray irradiation. The removal efficiency of cyanobacteria was95.5%at five days after gamma-ray irradiation when a dose of lOkGy was selected. The contents of photosynthetic pigment and protein considerably decreased as the increase of radiation dose. The low gamma irradiation doses enhanced the activity of SOD and POD in cyanobacterial cells. However, the relatively high gamma irradiation doses reduced the activity of these enzymes. The increase of MDA concentration in irradiated cyanobacterial cells indicated the lipid peroxidation by gamma-ray irradiation.(4) The non-thermal plasma produced by dielectric barrer discharge could remove the bloom cyanobacteria in Taihu Lake. The effects of discharge power, air flow rate, various additives on the removal efficiency of cyanobacteria were discussed. When100W discharge power,1.0L/min air flow rate,18min discharge time,20001x light intensity and4d culture time at25℃were selected, the removal efficiency of bloom cyanobacteria was over87.8%(the initial Chl-a concentration of cyanobacteria was9.58mg/L). The removal efficiency was increased with the increase of discharge power and air flow rate. The contents of Carotenoid and malondialdehyde, the activity of SOD and POD in cyanobacterial cells were changed, and the intracellular materials of cyanobacteria were damaged after treatment.(5) Gamma-ray irradiation significantly inhibited the recovery of overwintering cyanobacteria in Taihu water. The increase of absorbed dose enhanced the inhibition effect. The ratio of chlorophyll a, chlorophyll b and phycocyanin in water with the dose of5kGy were8.66%、16.8%and17.2%to that in contrast sample after40days culture. The recovery of overwintering cyanobacteria in surface sediments was also inhibited by gamma-ray irradiation. When a13kGy dose of irradiation was selected, the ratio of chlorophyll a, chlorophyll b and phycocyanin in culture medium were18.8%、14.8%and20.5%to that in contrast sample after60days culture.更多还原