纳米银与苯酚对反硝化菌活性的复合毒性效应与机制研究

发布时间：2018-06-09 11:34

本文选题：纳米银 + 苯酚　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：纳米银广泛用于日常生活中,随着纳米银的广泛应用,其潜在的环境生物效应也不容忽视。从消费品中释放出的纳米银很可能随生活污水进入到下水道系统中,进而进入污水处理厂中,而纳米银的存在对于污水生物处理系统中的微生物具有一定的毒害作用。此外,苯酚也普遍存在于各个行业的废水中,其也具有较高的生物毒性。部分研究已经证明纳米银和苯酚分别对微生物有一定的抑制作用,而有关对反硝化细菌影响的研究较少。因此本文以反硝化菌为模式菌株,分别通过构建纳米银与苯酚暴露实验系统,研究两者对细菌反硝化活性影响以及机制研究,且通过纳米银与苯酚复合污染,探究两者对细菌复合毒害效应。本文将细菌分别暴露于含有不同浓度的纳米银(0.1~30mg/L)和苯酚(0.05~6mg/L)培养基中,检测细菌反硝化能力。当投加纳米银浓度为1mg/L时,细菌的NO3--N还原速率k为0.15mg/(L·h),细菌反硝化能力受到一定程度影响。通过透射电镜(TEM)观察发现细菌细胞膜表面比较粗糙,且乳酸脱氢酶(LDH)释放率为149%,细菌胞内产生活性氧(ROS)含量是空白组的6.97倍,随着投加纳米银浓度的增加细菌反硝化能力明显降低。苯酚对细菌毒性较高,当苯酚投加浓度为0.1mg/L时,NO3--N还原速率仅为0.17mg/(L·h);细菌细胞膜完整性受到影响,LDH释放率为132%,NR比活性为0.14;而当苯酚投加浓度?5mg/L时,细菌几乎完全丧失活性。改变细菌培养温度和p H,细菌的增值和酶活受到严重的影响,对有机物代谢主要途径也有影响。当p H6或者p H?8时,细菌NO3--N还原速率明显降低,培养基中细菌数量骤减。但是培养环境的改变并不能降低纳米银和苯酚的生物毒性,较差的培养环境使细菌生长状态较差,此时较低浓度的纳米银和苯酚则会明显降低细菌反硝化活性,使LDH释放率较最佳环境培养时高。纳米银与苯酚之间会发生一定的吸附效应,不同接触温度下,纳米银对苯酚的吸附平衡点会有所改变,且到达平衡时苯酚吸附量也不同。较低的接触温度,使得纳米银与苯酚之间的吸附作用时间较长,达到平衡时苯酚吸附量较高。细菌经不同复合比例的纳米银与苯酚复合污染时,反硝化能力受到更加强烈的抑制。通过联合毒性效应评价纳米银与苯酚的复合效应,不同复合比例的AI值均大于零,两者之间是协同作用,说明苯酚与纳米银两者组成的混合物具有更高毒性,对自然界水处理系统中的微生物群落造成更大威胁,为复合毒性研究结论提供了理论依据。
[Abstract]:Nano-silver is widely used in daily life, and its potential environmental biological effects can not be ignored with the wide application of nano-silver. The silver nanoparticles released from consumer products are likely to enter the sewage system with the domestic sewage and then into the sewage treatment plant. The presence of nano-silver has a certain toxic effect on the microorganisms in the sewage biological treatment system. In addition, phenol also exists in wastewater of various industries and has high biotoxicity. Some studies have shown that nano-silver and phenol can inhibit microbes respectively, but few studies have been done on denitrifying bacteria. In this paper, denitrifying bacteria were used as model strains to study the effects of nano-silver and phenol exposure system on denitrification activity and the mechanism of denitrification. To explore the compound toxic effect of the two to bacteria. In this paper, bacteria were exposed to different concentrations of silver nanocrystalline (0.1 mg / L) and phenol (0.05 mg / L) to determine the denitrification ability of bacteria. When the concentration of nano-silver was 1 mg / L, the reduction rate of NO3-N was 0.15 mg / L, and the denitrification ability of bacteria was affected to some extent. The surface of bacterial cell membrane was rough and the release rate of lactate dehydrogenase (LDH) was 149%. The content of reactive oxygen species (Ros) produced by bacteria was 6.97 times of that in the blank group. The denitrification ability of bacteria decreased with the increase of the concentration of silver nanoparticles. The toxicity of phenol to bacteria was higher, when the concentration of phenol was 0.1 mg / L, the reduction rate of NO3-N was only 0.17 mg / L, the release rate of LDH was 0.14 when the cell membrane integrity was affected and the specific activity of NR was 0.14 when the concentration of phenol was 0.1 mg / L, and the bacteria almost completely lost its activity when the concentration of phenol was 5 mg / L. By changing the culture temperature and pH of bacteria, the increment and enzyme activity of bacteria were seriously affected, and the main pathway of organic matter metabolism was also affected. When pH 6 or pH? 8, the reduction rate of NO3-N decreased significantly, and the number of bacteria in culture medium decreased sharply. However, the change of culture environment could not reduce the biological toxicity of silver nanoparticles and phenol, and the lower concentration of silver nanoparticles and phenol could significantly reduce the denitrification activity of bacteria. The release rate of LDH was higher than that in the optimal environment. The adsorption equilibrium point of phenol was changed at different contact temperature, and the adsorption amount of phenol was also different when the equilibrium was reached. With the lower contact temperature, the adsorption time between silver nanoparticles and phenol is longer, and the adsorption amount of phenol is higher when the equilibrium is reached. The denitrification ability of bacteria was inhibited more strongly when the bacteria were polluted by nano-silver and phenol. The composite effect of nano-silver and phenol was evaluated by the combined toxicity effect. The AI values of different composite ratios were all greater than zero, which indicated that the mixture composed of phenol and nano-silver was more toxic. It poses a greater threat to the microbial community in the natural water treatment system and provides a theoretical basis for the conclusion of the compound toxicity study.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703;X172

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