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

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.

Key words:Inner Mongolia section of the Yellow River;nitrous oxide;community diversity;concentration and flux;influencing factors