Isotope Signatures of N2O in a Mixed Microbial Population System: Constraints on N2O Producing Pathways in Wastewater Treatment

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• 作者：Pascal Wunderlin ; Moritz F. Lehmann ; Hansruedi Siegrist ; B茅la Tuzson ; Adriano Joss ; Lukas Emmenegger ; Joachim Mohn
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：February 5, 2013
• 年：2013
• 卷：47
• 期：3
• 页码：1339-1348
• 全文大小：463K
• 年卷期：v.47,no.3(February 5, 2013)
• ISSN：1520-5851

文摘

We present measurements of site preference (SP) and bulk p>15p>N/p>14p>N ratios (未p>15p>Np>bulkp>_N2O) of nitrous oxide (N₂O) by quantum cascade laser absorption spectroscopy (QCLAS) as a powerful tool to investigate N₂O production pathways in biological wastewater treatment. QCLAS enables high-precision N₂O isotopomer analysis in real time. This allowed us to trace short-term fluctuations in SP and 未p>15p>Np>bulkp>_N2O and, hence, microbial transformation pathways during individual batch experiments with activated sludge from a pilot-scale facility treating municipal wastewater. On the basis of previous work with microbial pure cultures, we demonstrate that N₂O emitted during ammonia (NH₄p>+p>) oxidation with a SP of 鈭?.8 to 5.6 鈥?derives mostly from nitrite (NO₂p>鈥?/sup>) reduction (e.g., nitrifier denitrification), with a minor contribution from hydroxylamine (NH₂OH) oxidation at the beginning of the experiments. SP of N₂O produced under anoxic conditions was always positive (1.2 to 26.1 鈥?, and SP values at the high end of this spectrum (24.9 to 26.1 鈥? are indicative of N₂O reductase activity. The measured 未p>15p>Np>bulkp>_N2O at the initiation of the NH₄p>+p> oxidation experiments ranged between 鈭?2.3 and 鈭?7.6 鈥?(corresponding to a nitrogen isotope effect 螖未p>15p>N = 未p>15p>N_substrate 鈥?未p>15p>Np>bulkp>_N2O of 43.5 to 58.8 鈥?, which is considerably higher than under denitrifying conditions (未p>15p>Np>bulkp>_N2O 2.4 to 鈭?7 鈥? 螖未p>15p>N = 0.1 to 19.5 鈥?. During the course of all NH₄p>+p> oxidation and nitrate (NO₃p>鈥?/sup>) reduction experiments, 未p>15p>Np>bulkp>_N2O increased significantly, indicating net p>15p>N enrichment in the dissolved inorganic nitrogen substrates (NH₄p>+p>, NO₃p>鈥?/sup>) and transfer into the N₂O pool. The decrease in 未p>15p>Np>bulkp>_N2O during NO₂p>鈥?/sup> and NH₂OH oxidation experiments is best explained by inverse fractionation during the oxidation of NO₂p>鈥?/sup> to NO₃p>鈥?/sup>.