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The Effect And Mechanism Of Several Nanoparticles (Tio2,ZnO, Ag And Au) Upon Ammoxidation

Posted on:2013-11-02Degree:MasterType:Thesis
Country:ChinaCandidate:Z ChenFull Text:PDF
GTID:2231330374960656Subject:Environmental Engineering
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In order to understand the effects of nano-materials (gold, silver, TiO2and ZnO nanoparticles) on ammoxidation in the environment and their potential mechanisms, the enrichment cultures of (ammonia oxidizing bacteria) AOB, cultured from surface sediments from Jiulong River estuary wetland in Fujian province, China, were inoculated under the treatments with different concentrations of nano-materials (such as nano-silver, nano-gold nano-TiO2and nano-ZnO) for45days. Then the changes of ammonia nitrogen and nitrite nitrogen concentration, and the ammoxidation rate were measured, and the biodiversity of AOB and the abundance of amoA gene were analyzed by the methods of molecular fingerprint technology of PCR-DGGE and qPCR to determine the influence regularity among ammoxidation rate, the diversity of AOB and the abundance of amoA gene. In this paper, the main conclusions could be summarized as below:(1). Nano-silver significantly inhibited ammoxidation in the environment, the average ammoxidation rate was significantly positive related to Shannon index, Simpson index and the abundance of amoA gene of AOB. Nano-TiO2could also inhibited ammoxidation under exposing a higher concentration, the average ammoxidation rate was significantly positive related to Shannon index, Simpson index, evenness index and the abundance of amoA gene of AOB. Obviously, the inhibition of ammoxidation in the environment resulted mainly from the reduction of the biodiversity and the abundance of AOB, which caused by the bactericidal ability of nano-silver or nano-TiO2. Additionally, nano-ZnO could also cause slight concentration-dependant-promotion upon the consumption of ammonia nitrogen, but the average ammoxidation rate was negative related to the abundance of amoA gene. However, there was insignificant correlation among average ammoxidation rate, biodiversity and the abundance of AOB and under the treatment of nano-gold. And there was no inhibition upon AOB and ammoxidation average rate, yet a slight promotion of ammoxidation with nano-gold.(2). The DNA sequencing found the AOB tested in this research was belonged to β-Proteobacteria, which was closed to Nitrosospira or Nitrosomonas. Undoubtedly, the species of AOB in the environment is complicated, and the surrounding conditions in the environment are various as well. Therefore, more attention is still necessary to be paid to how and to what extent different nano-materials influence diversity and abundance of AOB and in turn ammoxidation.Figure [17] table [13] reference [106]...
Keywords/Search Tags:nano-materials, ammoxidation, community structure, abundance, nitrogen cycling
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