Managing Ammonia for Multiple Benefits Based on Verified High-Resolution Emission Inventory in China

Atmospheric
ammonia (NH3) has multiple impacts on the
environment, climate change, and human health. China is the largest
emitter of NH3 globally, with the dynamic inventory of
NH3 emissions remaining uncertain. Here, we use the second
national agricultural pollution source censuses, integrated satellite
data, 15N isotope source apportionment, and multiple models
to better understand those key features of NH3 emissions
and its environmental impacts in China. Our results show that the
total NH3 emissions were estimated to be 11.2 ± 1.1
million tonnes in 2020, with three emission peaks in April, June,
and October, primarily driven by agricultural sources, which contributed
74% of the total emissions. Furthermore, employing a series of quantitative
analyses, we estimated the contribution of NH3 emissions
to ecosystem impacts. The NH3 emissions have contributed
approximately 22% to secondary PM2.5 formation and a 16.6%
increase in nitrogen loading of surface waters, while ammonium deposition
led to a decrease in soil pH by 0.0032 units and an increase in the
terrestrial carbon sink by 44.6 million tonnes in 2020. Reducing agricultural
NH3 emissions in China would contribute to the mitigation
of air and water pollution challenges, saving damage costs estimated
at around 22 billion US dollars due to avoided human and ecosystem
health impacts.