The Dominant Role of the Water Column in Nitrogen Removal and N 2 O Emissions in Large Rivers

作者：Junfeng Wang, Xinghui Xia, Shaoda Liu, Sibo Zhang, Ling Zhang, Chenrun Jiang, Zhenrui Zhang, Yuan Xin, Xin Chen, Jing Huang, Jiaao Bao, William H. McDowell, Greg Michalski, Zhifeng Yang, Jun Xia · 发表于：Geophysical Research Letters · 年份：2022 · DOI：10.1029/2022gl098955 · 被引用次数：27 · 研究领域：Soil and Water Nutrient Dynamics、Marine and coastal ecosystems、Hydrology and Watershed Management Studies

Abstract Rivers are important sites for nitrogen (N) cycling processes. N removal is thought to occur predominantly in the benthic zone and the role of the water column is frequently neglected. Here, we find that the water‐air and sediment‐water fluxes of N 2 and N 2 O decreased, while the water column production increased with stream order through 4‐year observations across six river networks in China. The water column contribution increased with stream order and accounted for more than 50% in rivers above fifth order. The increase in the contact area of suspended sediment (SPS)‐water caused by higher SPS concentrations and river depths resulted in the shift as river size increased. N removal and N 2 O emissions would be underestimated approximately by 50% if neglecting water column processes for the six river networks. This study highlights the necessity and provides a pathway to incorporate water column processes into models to balance the global N budget.