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首页> 外文期刊>Estuarine Coastal and Shelf Science >The denitrification paradox: The role of O_2 in sediment N_2O production
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The denitrification paradox: The role of O_2 in sediment N_2O production

机译：反硝化悖论：O_2在沉积物N_2O产生中的作用

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We designed a novel laboratory sediment flux chamber in which we maintained the headspace O-2 partial pressure at preselected values, allowing us to experimentally regulate "in-situ" O-2 to evaluate its role in net N2O production by an intertidal estuarine sediment (Tyne, UK). In short-term (30 h) incubations with 10 L of overlying estuarine water (similar to 3 cm depth) and headspace O-2 regulation (headspace: sediment/ water ratio similar to 9:1), net N2O production was highest at 1.2% O-2 (sub-oxic; 32.3 nmol N2O m(-2) d(-1)), an order of magnitude higher than at either 0.0% (anoxic; 2.5 N2O nmol m(-2)) or 20.85% (ambient; 2.3 nmol N2O m(-2) d(-1)) O-2. In a longer-term sealed incubation (similar to 490 h) without O-2 control, time-dependent behaviour of N2O in the tank headspace was highly non-linear with time, showing distinct phases: (i) an initial period of no or little change in O-2 or N2O up to similar to 100 h; (ii) a quasi-linear, inverse correlation between O-2 and N2O to similar to 360 h, in which O-2 declined to similar to 2.1% and N2O rose to similar to 7800 natm; (iii) over the following 50 h a slower O-2 decline, to similar to 1.1%, and a more rapid N2O increase, to similar to 12000 natm; (iv) over the next 24 h a slowed O-2 decline towards undetectable levels and a sharp fall in N2O to similar to 4600 natm; (iv) a continued N2O decrease at zero O-2, to similar to 3000 natm by similar to 490 h. These results show clearly that rapid N2O consumption (similar to 115 nmol m(-2) d(-1)), presumably via heterotrophic denitrification (HD), occurs under fully anoxic conditions and therefore that N2O production, which was optimal for sub-oxic O-2, results from other nitrogen transformation processes. In experiments in which we amended sediment overlying water to either 1 mM NH4+ or 1 mM NO3-, N2O production rates were 2-134 nmol N2O m(-2) d(-1) (NH4+ addition) and 0.4-2.2 nmol N2O m(-2) d(-1) (NO3- addition). We conclude that processes involving NH4+ oxidation (nitrifier nitrification; nitrifier denitrification; nitrification-coupled denitrification) are principally responsible for N2O production in Tyne sediments. Highest N2O production occurred under suboxic headspace (similar to 1.2 02%) incubations. Anoxic sediments where HD was isolated acted as periodic N2O sinks or relatively small sources of N2O. Our experimental approach thus gives valuable insight into the O-2 effect on N2O fluxes from intertidal sediments. (C) 2017 Elsevier Ltd. All rights reserved.
机译：我们设计了一个新颖的实验室沉积物通量室，在其中将顶空O-2分压保持在预选值，从而使我们能够通过实验方式调节“原位” O-2，以评估潮汐河口沉积物在净N2O产生中的作用（英国泰恩）。在短期（30小时）中，用10升上方河口水（约3厘米深度）和顶空O-2调节（顶空：沉积物/水之比类似于9：1）孵育，N2O净产量最高，为1.2 ％O-2（低氧； 32.3 nmol N2O m（-2）d（-1）），比0.0％（缺氧； 2.5 N2O nmol m（-2））或20.85％（室温； 2.3nmol N 2 O m（-2）d（-1））O-2。在没有O-2控制的情况下进行的长期密封孵育（类似于490小时）中，N2O在罐顶空间中的时间依赖性行为随时间呈高度非线性，显示出不同的阶段：（i）初始阶段为无或直到100小时，O-2或N2O几乎没有变化； （ii）O-2和N2O之间的近似线性逆相关性接近360小时，其中O-2下降至相似的2.1％，N2O上升至相似的7800 natm； （iii）在接下来的50小时内，O-2的下降速度较慢，约为1.1％，N2O的上升较快，约为12000 natm； （iv）在接下来的24小时内，O-2的下降速度趋缓，降至无法检测的水平，N2O急剧下降至接近4600 natm； （iv）在零O-2下N2O持续减少，类似于3000 natm减少了490 h。这些结果清楚地表明，可能是通过异养反硝化（HD）快速消耗了N2O（类似于115 nmol m（-2）d（-1）），因此在完全缺氧的条件下会发生N2O的生产，这对于亚氧化是最佳的。其他氮转化过程产生的氧O-2。在我们将沉积物上覆水修正为1 mM NH4 +或1 mM NO3-的实验中，N2O的产生速率为2-134 nmol N2O m（-2）d（-1）（添加NH4 +）和0.4-2.2 nmol N2O m （-2）d（-1）（NO3-加成）。我们得出的结论是，涉及NH4 +氧化的过程（硝化器硝化；硝化器反硝化；硝化耦合反硝化）主要负责泰恩河沉积物中N2O的产生。 N2O的最高产量发生在低氧顶空条件下（约1.2 02％）。隔离了HD的缺氧沉积物充当了周期性的N2O汇或相对较小的N2O来源。因此，我们的实验方法对潮间带沉积物的O-2对N2O通量的影响提供了有价值的见解。 （C）2017 Elsevier Ltd.保留所有权利。

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    《Estuarine Coastal and Shelf Science》 |2018年第5期|270-276|共7页
  • 作者

    Barnes Jonathan; Upstill-Goddard Robert C.;

  • 作者单位

    Newcastle Univ, Sch Nat & Environm Sci, Oceans & Climate Res Grp, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England;

    Newcastle Univ, Sch Nat & Environm Sci, Oceans & Climate Res Grp, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England;

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