纳米乳化油修复硝酸盐污染地下水过程中的微生物特征模拟实验研究

为探寻纳米乳化油原位修复地下水硝酸盐氮污染过程中微生物堵塞的形成原因，本研究采用市售的反硝化细菌接种微生物，以纳米乳化油为碳源，中砂为介质，分别建立2组反应器进行模拟实验，分析不同反应器中硝氮的降解情况，同时采用MiSeq高通量测序技术表征不同反应器的微生物菌落结构和多样性.结果表明，纳米乳化油作为碳源具有良好的降解效果，添加纳米乳化油的反应器，反应周期内硝酸盐氮的总降解效率为91.76%，而对照反应器的降解效率仅为38.11%.在硝酸盐氮降解过程中，均存在以蛋白质和多糖为主的代谢产物胞外聚合物增加的趋势，且蛋白质的含量均显著高于多糖.反应结束时，实验组和对照组的胞外聚合物累积量分别为384.49 mg和279.45 mg，单位质量硝氮降解产生的胞外聚合物分别为1.79 mg·mg^-1和39.43 mg·mg^-1.高通量测序结果显示，添加纳米乳化油会引起细菌浓度的升高及细菌群落多样性的降低，但具有反硝化作用的微生物相对丰度增加.实验组和对照组反应器中共同的优势菌门为Proteobacteria、Bacteroidetes和Actinobacteria，相对丰度分别为73.35%、6.77%、8.49%及33.46%、47.15%、7.15%，纳米乳化油的添加会刺激Proteobacteria等具有较高反硝化作用的微生物增多，因此，以纳米乳化油作为碳源能够有效提高硝酸盐氮的降解效率，但与此同时纳米乳化油也会刺激微生物的生长及影响微生物群落演变.Sphingamonas、Rhodopseudomonas和Microbacterium菌属相对丰度增加，会引起粘性代谢产物增多，造成多孔介质渗透性下降和生物堵塞.

Experimental study of microbial characteristics in the process of in-situ nitrate pollution remediation by nano emulsified oil

To explore the causes of bioclogging in the process of in-situ nitrate pollution remediation by nano emulsified oil, experiments were conducted with reactors in which microorganisms were inoculated by commercial denitrifying bacteria, and nano emulsified oil and medium sands were used as carbon source and porous media, respectively. The nitrate degradation was evaluated and the variation of microorganisms community structure and diversity were characterized by the MiSeq high-throughput sequencing technology. The results showed that nano emulsified oil performed as a good degradation carbon source. The total degradation efficiency of nitrate in the reactor with nano emulsified oil reached 91.76%, but in the control reactor without nano emulsified oil, it is only 38.11%. In the process of nitrate degradation, extracellular polymers with proteins and polysaccharides as the main components showed an increasing trend in all reactors, and proteins content was significantly higher than that of polysaccharides. At the end of experiments, the cumulative amounts of extracellular polymers in the experimental group and the control group were 384.49 mg and 279.45 mg, and the average extracellular polymeric substance production corresponding to the degradation of nitrate nitrogen per unit mass were 1.79 mg·mg^-1 and 39.43 mg·mg^-1, respectively. The High-throughput sequencing analyses indicated that addition of nano emulsified oil resulted in an increase in bacterial concentration and a decrease in bacterial community diversity, but a proliferation in denitrifying bacteria. Proteobacteria, Bacteroidetes and Actinonobacteria were the dominant groups on the phylum level in all reactors. Their relative abundance were 73.35%, 6.77% and 8.49% in the experimental reactors and 33.46%, 47.15% and 7.15% in the control reactors, respectively. The reason was that that nano emulsified oil could stimulate the proliferation of denitrifying microorganisms, such as Proteobacteria. Therefore, as a carbon source, Nano emulsified oil could effectively improve the degradation efficiency of nitrate. Meanwhile, it could stimulate the growth of microorganisms and affect the evolution of microbial communities. It was concluded that the increase in relative abundance of Sphingamonas, Rhodopseudomonas and Microbacterium could lead to the increase in production of extracellular polymers and consequently result in the decrease of permeability of porous media and aquifers clogging.