黄河内蒙古段水体氧化亚氮溶存浓度、水-气界面排放通量和沉积物微生物群落结构

Dissolved concentration of nitrous oxide,water-air interface emission flux,and sediment microbial community structure in the Inner Mongolia section of the Yellow River

摘要:

【目的】基于全球气候治理背景以及黄河流域在我国生态文明建设中的重要地位，本研究于2023年7月选择黄河内蒙古段流域为对象，测定流域内表层沉积物微生物群落结构与多样性、水体理化性质及水-气界面氧化亚氮(nitrous oxide,N₂O)气体通量。【方法】使用静态箱-气相色谱仪法对黄河内蒙古段水体N₂O溶存浓度、水-气界面N₂O排放通量进行探究，使用高通量测序分析表层沉积物。【结果】结果表明黄河内蒙古段水体N₂O溶存浓度变化范围在0.547 8−0.598 2 mg/m³之间，均值为0.574 1 mg/m³，水-气界面N₂O排放通量(FN₂O)变化范围为−3.645 3−4.392 5 mg/(m²·d)，均值为1.086 1 mg/(m²·d)，总体表现为大气N₂O的“源”。FN₂O和pH呈极显著正相关、和电位呈显著负相关。表层沉积物中细菌共有7 784个操作分类单元(operational taxonomic unit,OTU)，其中变形菌门(Proteobacteriota)以平均35.13%的丰度成为最优势菌群。氨氧化古菌(ammonia-oxidizing archaea,AOA)相关基因丰度较低，检测到116个OTUs，unclassified_d__Unclassified为优势菌属(平均丰度为31.69%)。反硝化细菌共有3 660个OTUs，优势菌属为unclassified_k__norank_d__Bacteria(平均丰度为63.12%)。【结论】由于黄河内蒙古段N₂O相关数据较少，因此本研究结果对填补江河N₂O数据具有积极意义，为进一步了解沉积物微生物群落结构及功能菌在黄河治理中的应用提供参考，有助于黄河的保护和净化计划。

Abstract:

[Objective]Within the framework of global climate governance and considering the pivotal role of the Yellow River basin in China’s ecological progress,this study focused on the Inner Mongolia segment of the Yellow River in July 2023.[Methods]We collected the surface sediment,water,and gas samples,with the aim of investigating the dissolved nitrous oxide (N₂O) concentration in the water,the N₂O emission flux (FN₂O) at the water-air interface,and the microbial community composition and diversity in surface sediments.[Results] The results revealed that the dissolved nitrous oxide (N₂O) concentration in the water of this segment varied between 0.547 8 mg/m³ and 0.598 2 mg/m³,with an average of 0.574 1 mg/m³.The FN₂O at the water-air interface ranged from−3.645 3 mg/(m²·d) to 4.392 5 mg/(m²·d),averaging 1.086 1 mg/(m²·d),which suggested this area was a net source of atmospheric N₂O.FN₂O showed a significantly positive correlation with pH and a significantly negative correlation with potential.The surface sediments harbored 7 784 operational taxonomic units (OTUs),with Proteobacteria (average abundance of 35.13%) being dominant.Ammonia-oxidizing archaea (AOA),a category of nitrifying bacteria,presented low abundance,with 116 OTUs among which unclassified_d__Unclassified(average abundance of 31.69%) was the dominant genus.For denitrifying bacteria,3 660 OTUs were identified,with unclassified_k__norank_d__Bacteria(average abundance of 63.12%) being the dominant genus.In view of the scarcity of N₂O data for the Inner Mongolia section of the Yellow River,the findings of this study enrich the N₂O data repository of the Yellow River.[Conclusion] This study not only augments our understanding of the microbial community structure and functionality in sediments but also supports the conservation and purification of the Yellow River.