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首页> 外文期刊>Geochemical Journal >Isotopocule characterization of N2O dynamics during simulated wastewater treatment under oxic and anoxic conditions
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Isotopocule characterization of N2O dynamics during simulated wastewater treatment under oxic and anoxic conditions

机译：在有氧和无氧条件下模拟废水处理过程中N2O动力学的等位表征

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Isotopocule ratios of N2O (delta N-15, delta O-18 and SP = N-15 site preference within the linear N2O molecule) are useful parameters to identify sources of this greenhouse gas and provide an insight into production and consumption mechanisms in a complex bacterial system. We measured isotopocule ratios of dissolved N2O in simulated wastewater with activated sludge under variable conditions of key factors including dissolved oxygen (DO), carbon-to-nitrogen ratio (C/N ratio), mixed liquor suspended solid (MLSS), and water temperature in oxic and anoxic conditions. Under oxic condition, lower DO concentration causes greater N2O accumulation. Observed low SP (-2.6 to +7.8% at 25 degrees C and -7.2 to +9.2% at 18 degrees C), which is unique to N2O production pathway, and the relation of nitrogen isotope ratios between N2O and its substrate (NH4+) suggests that N2O is produced mainly by NO2- reduction by autotrophic nitrifiers (nitrifier-denitrification). The N2O production mechanism in this condition was not altered by changes in DO of 0.5-3.0 mg L-1. Under anoxic conditions, NO2- reduction by denitrifying bacteria (heterotrophic denitrification) is the dominant contributor to N2O production. Also, N2O reduction to N-2 occurred simultaneously, as implied by isotopocule analysis. The C/N ratio had a negligible effect on the N2O production mechanism. During anoxic N2O decomposition experiment, a positive correlation between delta O-18 and delta N-15(bulk) (slope = 2.2) and between SP and N-15(bulk) (slope = 0.9) of N2O, which indicates the occurrence of N2O reduction, were found. The N2O reduction rate was increased by the high MLSS concentration. Moreover, isotopic enrichment factors (epsilon), which are specific to biological reaction, during N2O reduction were estimated as -9.5 +/- 1.0% for delta N-15(bulk), -28.7 +/- 3.7% for delta O-18 and -10.0 +/- 2.2% for SP of N2O.
机译：N2O的等容比（线性N2O分子内的Delta N-15，Delta O-18和SP = N-15位点优先）是有用的参数，可用于识别这种温室气体的来源并提供对复杂环境中生产和消费机制的了解细菌系统。我们在可变条件下测量了含活性污泥的模拟废水中溶解态N2O的同位素比值，这些条件包括溶解氧（DO），碳氮比（C / N比），混合液悬浮固体（MLSS）和水温在有氧和无氧条件下。在有氧条件下，较低的DO浓度会导致较大的N2O积累。观察到低SP（在25摄氏度时为-2.6至+ 7.8％和在18摄氏度时为-7.2至+ 9.2％），这是N2O产生途径所独有的，以及N2O及其底物（NH4 +）之间的氮同位素比关系这表明N2O主要是由自养硝化器（硝化器-反硝化）还原NO2-而产生的。在这种情况下，N2O的产生机理不会因DO的0.5-3.0 mg L-1的变化而改变。在缺氧条件下，反硝化细菌还原NO2（异养反硝化）是N2O产生的主要因素。同样，N2O还原为N-2的情况同时发生，这是由同位素检测所暗示的。 C / N比对N2O产生机理的影响可忽略不计。在缺氧的N2O分解实验中，δO-18和δN-15（大块）（斜率= 2.2）之间以及SP和N-15（堆积）（斜率= 0.9）之间的正相关关系表明发生了N2O。发现减少了N 2O。高MLSS浓度可提高N2O还原速率。此外，N2O还原过程中对生物反应具有特异性的同位素富集因子（ε）对于δN-15（散装）估计为-9.5 +/- 1.0％，对于δO-18估计为-28.7 +/- 3.7％对于SP的N2O为-10.0 +/- 2.2％。

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