Long-term effect of temperature on N₂O emission from the denitrifying activated sludge

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概要

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• The long-term effect of various temperature (4℃, 12℃, 20℃, 25℃ and 34℃) on nitrous oxide (N_2O) emission from lab-scale denitrifying activated sludge was studied in terms of activation energy, abundance of functional gene nosZ and its transcription. Results showed that temperature had a positive effect on N_2O emissions as well as the maximum biomass-specific reduction rates of N_2O and NO_3^-, ranging from 0.006% to 0.681% of (N_2O + N_2), 17.3-116.2 and 5.2-66.2 mg N g^<-1> VSS h^<-1>, respectively. The activation energies (Ea) for N_2O and NO_3^- reduction of 44.1 kJ mol^<-1> and 54.9 kJ mol^<-1>, shed light on differences in denitrifying rate variation. The maximum NO_3^- reduction rates were more sensitive to temperature variation than the corresponding N_2O reduction rates under long-term acclimation. As a result, the ratio between N_2O and NO_3^- reduction rates declined to 1.87 at 34℃ from 3.31 at 4℃, suggesting great potential capacity for N_2O losses at high temperature. The copy numbers of denitrifiers as nosZ gene (×10^8 copies mL^<-1>) and total bacteria as 16S rRNA gene (×10^<10> copies mL^<-1>) did not show obvious relationship with temperature, having relative abundance of 0.42% on average. The transcriptional regulation of nosZ gene, in the range of 10^8-10^5 copies mL^<-1>, was affected by reductase activity, substrate concentration as well as its duration. The active nosZ gene expression was accompanied with low reductase capacity, high dissolved N_2O and the duration of N_2O accumulation. These results provide insights into activation energy and gene expression responsible for N_2O emission.

著者

• WANG Xiaojun

  Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and physics

• Kao Chih

  Institute of Environmental Engineering, National Sun Yat-Sen University

• Yang Xiaoru

  Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences

• Zhang Zhaoji

  Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences

• Ye Xin

  Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences

• Chen Shaohua

  Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences

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• Long-term effect of temperature on N₂O emission from the denitrifying activated sludge

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