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Riverine nitrogen loss makes a large contribution to the global nitrogen budget. However, little research has focused on nitrogen loss from large turbid rivers with high suspended sediment (SPS) concentrations. In this work, nitrogen loss amounts and related drivers were studied across fluvial networks of the Yellow River, the largest turbid river in the world, based on in situ measurement of nitrogen gas (N 2 ) and nitrous oxide (N 2 O) fluxes at the water-air interface via the diffusion model and floating chamber methods, respectively. The results showed that N 2 and N 2 O fluxes from the Yellow River ranged from -2.93 to 48.54 mmol m -2 d -1 and from 2.42 to 712.23 μmol m -2 d -1 , respectively, with the nitrogen loss amount estimated to be 5.56 × 10 7  kg N yr -1 for the Yellow River, including the mainstem and main tributaries. Other than nitrogen compounds and water temperature, nitrogen loss from the Yellow River was also affected by SPS. Both N 2 flux: DIN and N 2 O flux: DIN ratios increased remarkably in the middle reaches, probably due to a sharp increase of SPS concentration in this section. Furthermore, greater SPS concentrations were a main cause for the higher N 2 O flux in the middle reaches than those in the other reaches of the Yellow River, and the possible effect of SPS was stronger on N 2 O flux than on N 2 flux. This study demonstrates the importance of SPS in nitrogen loss from large turbid rivers, and more research is demanded to further clarify the role of SPS in riverine nitrogen cycle., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Rivers are important sites of both nitrogen removal and emission of nitrous oxide (N 2 O), a powerful greenhouse gas. Previous measurements have focused on nitrogen-rich temperate rivers, with cold, low-nitrogen river systems at high-altitude receiving less attention. Here, nitrogen removal rates were estimated by directly measuring dissolved N 2 and N 2 O of the Yellow River in its source region of the Tibetan Plateau, a frigid high-altitude environment. We measured the dissolved N 2 and N 2 O using N 2 :Ar ratio method and headspace equilibrium technique, respectively. Dissolved N 2 in the river water ranged from 337 to 513 μmol N 2  L -1 , and dissolved N 2 O ranged from 10.4 to 15.4 nmol N 2 O L -1 . Excess dissolved N 2 (△N 2 ) ranged from -8.6 to 10.5 μmol N 2  L -1 , while excess dissolved N 2 O (△N 2 O) ranged from 2.1 to 8.3 nmol N 2 O L -1 ; they were relatively low compared with most other rivers in the world. However, N 2 removal fraction (△N 2 /DIN, average 21.6%) and EF 5r values (N 2 O - N/NO 3  - N, range 1.6 × 10 -4 -5.0 × 10 -2 ) were comparable with many other rivers despite the high altitude for the Yellow River source region. Furthermore, the EF 5r values increased with altitude. Estimated fluxes of N 2 and N 2 O to the atmosphere from the river surface ranged from -67.5 to 93.5 mmol N m -2  d -1 and from 4.8 to 93.8 μmol N m -2  d -1 , respectively, and the nitrogen removal from rivers was estimated to be 1.87 × 10 7  kg N yr -1 for the Yellow River source region. This is the first report of nitrogen removal for a frigid high-altitude river; the results suggest that N removal and N 2 O emission from cold high-altitude rivers should be considered in the global nitrogen budget., (Copyright © 2018 Elsevier B.V. All rights reserved.)