Ammonium-derived nitrous oxide is a global source in streams
Shanyun Wang, Bangrui Lan, Longbin Yu, Manyi Xiao, Liping Jiang, Yu Qin, Yucheng Jin, Yuting Zhou, Gawhar Armanbek, Jingchen Ma, Manting Wang, Mike S. M. Jetten, Hanqin Tian, Guibing Zhu, Yong‐Guan Zhu
Abstract
Abstract Global riverine nitrous oxide (N 2 O) emissions have increased more than 4-fold in the last century. It has been estimated that the hyporheic zones in small streams alone may contribute approximately 85% of these N 2 O emissions. However, the mechanisms and pathways controlling hyporheic N 2 O production in stream ecosystems remain unknown. Here, we report that ammonia-derived pathways, rather than the nitrate-derived pathways, are the dominant hyporheic N 2 O sources (69.6 ± 2.1%) in agricultural streams around the world. The N 2 O fluxes are mainly in positive correlation with ammonia. The potential N 2 O metabolic pathways of metagenome-assembled genomes (MAGs) provides evidence that nitrifying bacteria contain greater abundances of N 2 O production-related genes than denitrifying bacteria. Taken together, this study highlights the importance of mitigating agriculturally derived ammonium in low-order agricultural streams in controlling N 2 O emissions. Global models of riverine ecosystems need to better represent ammonia-derived pathways for accurately estimating and predicting riverine N 2 O emissions.