Benefits of refined NH emission controls on PM mitigation in Central China.

Atmospheric ammonia (NH) is one of the most crucial precursors of secondary inorganic aerosols. However, its emission control is still weakness over China. NH emission inventories of 2015 with and without considering a set of refined emission reduction strategies covering seven major NH emission sources were constructed in Central China. GEOS-Chem model simulations were conducted to quantify the benefits of NH emission reduction on PM mitigation in four typical months (January, April, July and October). The results showed that these control strategies could reduce approximately 47.0% (152 Gg) of the total NH emissions in Hubei Province, with the agricultural (livestock and fertilizer application) source being reduced the most (133 Gg). NH had a significant nonlinear relationship with sulfate, nitrate, ammonium and PM. NH emission reduction exerted less effect on sulfate mitigations (the annual average sensitivity was 4.5%), but it obviously alleviated nitrate, ammonium and thus PM, with the annual average sensitivities of 81.9%, 34.8% and 22.0%, respectively. The average provincial concentrations of PM were alleviated by 11.2% in January, 10.6% in October, 10.2% in April and 9.3% in July through NH emission reduction by 47.0%. The reduction benefits were more pronounced in high NH emission areas, such as Yichang, with the PM reduction of 14.4% in January. This research could provide scientific support for formulating NH emission reduction policies to further mitigate PM pollution.