Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions
Global carbon dioxide efflux from rivers enhanced by high nocturnal emissions
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DOI：
10.1038/s41561-021-00722-3
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发表时间：
2021-04-15
影响因子：
18.3
通讯作者：
Sponseller, Ryan A.
中科院分区：
文献类型：
--
作者：
Gomez-Gener, Lluis;Rocher-Ros, Gerard;Sponseller, Ryan A.
据估计，从流动的沃茨排放到大气中的二氧化碳（CO2）比排放到海洋中的总碳（C）通量高四倍。然而，由于溶解CO2浓度在空间和时间上的显著变化，这些通量仍然受到很差的约束。使用全球高频CO2测量汇编，我们证明夜间CO2排放量平均比仅从昼夜浓度估计的高27%（0.9 gC m（-2）d（-1））。由于冠层阴影或水的颜色的光可用性的限制是观察到的昼夜（24小时）变化的主要控制，这表明夜间增加产生白天固定的CO2通过光合作用。由于目前对流动沃茨向大气排放的CO2的全球估计（0.65-1.8 PgC yr（-1））主要依赖于白天获得的溶解CO2的离散测量，因此它们大大低估了这一通量的大小。根据对高频CO2测量结果的分析，如果考虑夜间CO2排放量，可能会使全球估计的从流动沃茨排放到大气中的CO2排放量增加0.20-0.55 PgC yr（-1）。如果不考虑昼夜之间的排放差异，将导致全球河流CO2排放量被低估0.55 PgC yr（-1）。
Carbon dioxide (CO2) emissions to the atmosphere from running waters are estimated to be four times greater than the total carbon (C) flux to the oceans. However, these fluxes remain poorly constrained because of substantial spatial and temporal variability in dissolved CO2 concentrations. Using a global compilation of high-frequency CO2 measurements, we demonstrate that nocturnal CO2 emissions are on average 27% (0.9 gC m(-2) d(-1)) greater than those estimated from diurnal concentrations alone. Constraints on light availability due to canopy shading or water colour are the principal controls on observed diel (24 hour) variation, suggesting this nocturnal increase arises from daytime fixation of CO2 by photosynthesis. Because current global estimates of CO2 emissions to the atmosphere from running waters (0.65-1.8 PgC yr(-1)) rely primarily on discrete measurements of dissolved CO2 obtained during the day, they substantially underestimate the magnitude of this flux. Accounting for night-time CO2 emissions may elevate global estimates from running waters to the atmosphere by 0.20-0.55 PgC yr(-1).Failing to account for emission differences between day and night will lead to an underestimate of global CO2 emissions from rivers by up to 0.55 PgC yr(-1), according to analyses of high-frequency CO2 measurements.