Rapid increase in China’s industrial ammonia emissions: evidence from unit-based mapping

Ammonia (NH3) is an important precursor of secondary inorganic aerosols
and greatly impacts nitrogen deposition and acid rain. Previous studies
have mainly focused on the agricultural NH3 emissions, while recent
research has noted that industrial sources could be significant in China.
However, detailed estimates of NH3 emitted from industrial sectors in
China are lacking. Here we established an unprecedented
high-spatial-resolution dataset of China’s industrial NH3 emissions using
up-to-date measurements of NH3 and point source-level information covering
eight major industries and 27 subdivided process categories. We found that
China emitted 798 (90% confidence interval: 668–933) gigagrams of
industrial NH3 to the atmosphere in 2019, equivalent to 44±20% of the
industrial emissions worldwide; this flux is three-fold larger than that
in 1998 and has fluctuated since 2014. Furthermore, although fertilizer
production is responsible for approximately half of the emissions in
China, the emissions from cement production and coal-fired power plants
increased dramatically from near zero to 164 and 41 gigagrams,
respectively, in the past two decades, primarily due to the NH3 escape
caused by the large-scale application of the denitration process. Our
results reveal that, unlike other major air pollutants, China’s industrial
NH3 emission control is still in a critical period, and stricter NH3
emission standards and innovation in pollution control technologies are
highly desirable.