Global nitrous oxide emissions from streams and rivers: A process-based modeling study
Date:
Nitrous dioxide (N2O) is the third important greenhouse gas after carbon dioxide (CO2) and methane (CH4) and also contributes to ozone depletion in the stratosphere. Previous studies are mainly focused on N2O emissions from soils; however, emissions from riverine systems are far from uncertain due to lack of observations and modeling framework. Here, we developed a process-based riverine N2O module based on a scale adaptive river routine scheme and coupled it with the dynamic land ecosystem model (DLEM) to quantify the global riverine N2O emission and its spatiotemporal variations from 1900 to 2016. Global riverine N2O emissions are further attributed to the controlling factors of climate variability, nitrogen (N) fertilizer and manure application, carbon dioxide (CO2) fertilization, and atmospheric nitrogen deposition.. Our results suggested that riverine N2O fluxes were tripled during the past century. Developing countries, such as China and India, accounted for more than 50% of the increased riverine N2O emission since 1980s. In contrast, riverine N2O emissions in developed countries reached their upper limits during the recent twenty years. Nitrogen fertilizer use has been the primary factor responsible for the increased riverine N2O emissions, followed by N deposition, N manure, and climate change. In the contrary, CO2 fertilization has a negative impact on riverine N2O emissions.