GEOGRAPHY

Studies have found that organic nitrogen aerosols contribute to nitrogen deposition in the global atmosphere


Recently, the team of Professor Fu Zongmei from the School of Environmental Science and Engineering of Southern University of Science and Technology and the team of Professor Yu Jianzhen of the Faculty of Environmental Studies of the Hong Kong University of Science and Technology published the latest research results in the National Science Review.

The research team revealed that atmospheric organic nitrogen is an important external nitrogen source in some “nitrogen-limited” ecosystems, and its ecological and environmental effects may expand with global warming and anthropogenic nitrogen oxide emission reduction, laying an important scientific foundation for quantitatively understanding atmospheric organic nitrogen sources and ecological environmental effects.

In this study, the researchers constructed a global atmospheric gaseous and granular organic nitrogen model, and quantitatively evaluated the sources, components, concentration distribution and contribution of global atmospheric organic nitrogen to total atmospheric nitrogen deposition. Studies have shown that the global atmospheric organic nitrogen deposition flux is 26 TgN per year, mainly particulate organic nitrogen deposition. Atmospheric organic nitrogen aerosols mainly come from wildfire emissions, marine emissions and secondary liquid phase generation, and the global atmospheric organic nitrogen aerosol deposition accounts for about 19% of the total atmospheric nitrogen deposition, but in the downstream of biomass combustion, it accounts for 40% to 80%.

The atmospheric deposition of organic nitrogen is an important part of the global nitrogen cycle, and about 2% to 70% of the total atmospheric nitrogen deposition flux is organic nitrogen. Previous studies have failed to analyze the heterogeneity of atmospheric organic nitrogen sources and their spatiotemporal and chemical components at the global scale, and failed to quantify the global atmospheric organic nitrogen deposition, resulting in a serious lack of understanding of the ecological and environmental effects of organic nitrogen deposition.

In this regard, the researchers constructed a complete model of atmospheric organic nitrogen, including the primary emission source, secondary (gas, liquid, heterogeneous) generation pathway and chemical evolution process of gaseous and granular organic nitrogen components. The model successfully simulated the global surface atmospheric organic nitrogen concentration, which was highly consistent with the observation. Simulations revealed that the global average concentration of surface organic nitrogen aerosols is 0.23 micrograms per cubic meter, most of which is present in the form of fine particulate matter, mainly from wildfires, liquid phase generation and anthropogenic emissions.

The study estimated the global atmospheric organic nitrogen deposition at 26 TgN per year, the vast majority of which is particulate organic nitrogen deposition, from wildfires, ocean emissions and liquid phase formation, respectively. Atmospheric organic nitrogen aerosol deposition accounts for about 19% of the total atmospheric nitrogen deposition flux worldwide. The model proposed in this study successfully simulated the high organic nitrogen deposition fluxes observed in tropical forests in South Asia, East Asia, Western Europe, Africa and South America, as well as in the forests of North America and Siberia, reflecting that wildfire burning and anthropogenic sources are the main contributors to organic nitrogen deposition in the terrestrial atmosphere.

It is further pointed out that the spatial heterogeneity of organic nitrogen deposition flux and organic nitrogen to total nitrogen deposition ratio is closely related to the source and chemical composition of organic nitrogen. Atmospheric organic nitrogen deposition is the main external nitrogen source in some “nitrogen-constrained” ecosystems, and its importance may be increased by increased wildfire emissions due to warming and increased ocean surface stability. In areas with intensive anthropogenic activities, the importance of organic nitrogen deposition will be further enhanced with the emission reduction of anthropogenic inorganic nitrogen. (Source: China Science News, Diao Wenhui)

Related paper information:https://doi.org/10.1093/nsr/nwad244

Research diagram Courtesy of SUSTech



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