Denitrification and DNRA in Urban Accidental Wetlands in Phoenix, Arizona
Denitrification and DNRA in Urban Accidental Wetlands in Phoenix, Arizona
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DOI：
10.1029/2021jg006552
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发表时间：
2022-01
期刊：
影响因子：
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通讯作者：
A. Handler;A. Suchy;N. Grimm
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文献类型：
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作者：
A. Handler;A. Suchy;N. Grimm
反硝化和异化硝酸盐还原为氨氮(DNRA)都需要低氧和高有机碳条件，这在湿地生态系统中是常见的。反硝化作用以气体的形式永久地从生态系统中去除氮，而DNRA通过生产铵来回收生态系统中的氮。反硝化作用与DNRA的相对盛行程度对生态系统中硝酸盐的命运有影响。与非城市湿地相比，美国亚利桑那州凤凰城附近盐河河道中未经规划和管理的城市意外湿地具有较高的硝酸盐含量，具有很高的反硝化能力，但对DNRA的能力尚不清楚。我们用同位素标记的硝酸盐进行了原位推拉试验，以测量这些城市偶然湿地中三种主要植被斑块的反硝化和DNRA速率。在硝酸盐还原(DNRA加反硝化)中，DNRA占2%到40%，与香蒲相比，Ludwigia peploides斑块的硝酸盐还原速率最高。和非植被斑块。湿地斑块在溶解有机碳浓度方面相似，但由于凋落物分解和通过扩散和曝气组织提供氧气，湿地斑块在碳稳定性或还原条件强度方面可能有所不同。DNRA与反硝化的比值与硝酸盐浓度呈负相关，表明DNRA在低浓度下可能成为硝酸盐衰减的重要途径。尽管DNRA一般低于反硝化作用，但在这些未经管理的城市偶然湿地中，这一途径是某些斑块内硝酸盐衰减的重要组成部分。
Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) both require low oxygen and high organic carbon conditions common in wetland ecosystems. Denitrification permanently removes nitrogen from the ecosystem as a gas while DNRA recycles nitrogen within the ecosystem via production of ammonium. The relative prevalence of denitrification versus DNRA has implications for the fate of nitrate in ecosystems. Unplanned and unmanaged urban accidental wetlands in the Salt River channel near downtown Phoenix, Arizona, USA receive high nitrate relative to non‐urban wetlands and have a high capacity for denitrification, but unknown capacity for DNRA. We conducted in‐situ push‐pull tests with isotopically labeled nitrate to measure denitrification and DNRA rates in three of the dominant vegetative patch types in these urban accidental wetlands. DNRA accounted for between 2% and 40% of nitrate reduction (DNRA plus denitrification) with the highest rates measured in patches of Ludwigia peploides compared to Typha spp. and non‐vegetated patches. The wetland patches were similar with respect to dissolved organic carbon concentration but may have differed in carbon lability or strength of reducing conditions due to a combination of litter decomposition and oxygen supply via diffusion and aerenchyma. The ratio of DNRA to denitrification was negatively correlated with nitrate concentration, indicating that DNRA may become a more important pathway for nitrate attenuation at low nitrate concentration. Although DNRA was generally lower than denitrification, this pathway was an important component of nitrate attenuation within certain patches in these unmanaged urban accidental wetlands.