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首页> 外文期刊>Aquatic Sciences >Effects of a diel oxygen cycle on nitrogen transformations and greenhouse gas emissions in a eutrophied subtropical stream
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Effects of a diel oxygen cycle on nitrogen transformations and greenhouse gas emissions in a eutrophied subtropical stream

机译：Diel氧气循环对富营养的亚热带水流中氮转化和温室气体排放的影响

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摘要

Rivers and streams constitute a major pathway for material transport from land to sea and an important source of greenhouse gases. Short-term variation in stream chemistry due to day-night oxygen (O_2) fluctuations could significantly affect a stream's capacity to transport nutrients and produce greenhouse gases. Though it is well established that diel cycles are important in controlling O_2 and CO_2 dynamics, the study of diel dynamics of other redox-sensitive elements has been fairly limited. Here we show that a subtropical stream can undergo complete reduction and oxidation sequences in just a few hours. This redox fluctuation has important consequences for downstream transfer of nutrients and for greenhouse gas pro- duction. Among these consequences are decreased deni-trification rates relative to estimates made using only daytime measurements (17-38% during our observation period), increased downstream nitrogen (N) transfer, a striking change in form of transported N (decreased nitrate and increased ammonium), and decreased estimates of in-stream nitrous oxide (N_2O) flux (36-38% during our observation period). Additionally, methane (CH_4) concentrations doubled and carbon dioxide (CO_2) concentrations rose from 4.6 to 30.7 mg L~(-1) during the 24-hour period of our observations. Diel shifts like the one we describe have implications for our understanding of nutrient transport and greenhouse gas production in eutrophied streams.
机译：河流和小溪构成了从陆地到海洋的物质运输的主要途径，也是温室气体的重要来源。由于昼夜氧气（O_2）的波动，河流化学物质的短期变化可能会严重影响河流的养分输送能力和产生温室气体的能力。尽管已经充分认识到，迪尔循环对控制O_2和CO_2的动力学很重要，但对其他氧化还原敏感元素的迪尔动力学的研究却相当有限。在这里，我们表明，亚热带气流可以在短短几个小时内完成完整的还原和氧化过程。这种氧化还原波动对营养物质的下游转移和温室气体的产生具有重要的影响。这些后果包括相对于仅使用日间测量值估算的脱硝率降低（在我们的观察期内为17-38％），下游氮（N）转移增加，氮的转运形式发生了显着变化（硝酸盐减少和铵盐增加） ），并减少了估算中的一氧化二氮（N_2O）通量（在我们的观察期内为36-38％）。此外，在我们观察的24小时内，甲烷（CH_4）浓度增加了一倍，二氧化碳（CO_2）浓度从4.6升至30.7 mg L〜（-1）。像我们描述的那样，狄尔变换对我们对富营养化流中的营养物质运输和温室气体产生的理解具有影响。

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