Effectiveness of synergistic abatement for emissions of NOX and NH3 to mitigate nitrate-dominated aerosols in a typical city, northern China

Since the effective control of SO2 emissions in current years, nitrate has become an increasingly dominant component of aerosol during winter in northern China. Water-soluble inorganic ions (WSIIs) in fine particulate matter (PM2.5) from November 2017 to March 2018 were analyzed in northern China to explore the effective control strategies for mitigating aerosols pollution. Daily variation of PM2.5 concentration ranged from 17.9 μg m−3 to 173.3 μg m−3 with the average of 70.3 μg m−3 during the sampling period. NO3− was the major components in WSIIs (31.5%) and largest increase of its proportions (6.3%) in WSIIs in pollution days was found when compared with clean days. Nitrate-dominated aerosols were mainly observed in the region that was sensitive to the total nitrate (TNO3) and some were in the region that was sensitive to the total ammonium (NHx). Simulating the response of nitrate aerosols to the individual reduction of SO42−, TNO3, and NHx, respectively, revealed that NHx reduction had the non-linear but the greatest impact on the concentration of NO3− and SIA in PM2.5 while TNO3 reduction cause the non-highest but linear impact. Individual reduction of NHx or TNO3 was suitable in long-term and short-term for mitigating aerosols pollution, respectively. Hence, Impact of synergistic abatement of NHx and TNO3 on nitrate-dominated aerosols was further explored. When the total reduction ratio of NHx and TNO3 reached 80%, NHx/TNO3 = 1:3 could cause the decrease highest on SIA and total ions concentrations (58.4% and 46.4%, respectively) in the eleven reduction scenarios, indicating that synergistic abatement of NOX and NH3 is more effective than individual reduction to mitigate aerosol pollution. This work improves our understanding about the effects of synergistic abatement of NH3 and NOX on SIA formation and provides new insights into the mitigation of aerosol pollution. [Display omitted] •Nitrate as the major component of PM2.5 significantly increased in pollution days.•Formation process of PM2.5 was mainly sensitive to TNO3 and some to NHx.•PM2.5 respond highest but non-linear for NHx while linear but non-highest for TNO3.•NHx/TNO3 = 1:3 would be the most effective reduction ratio for reducing PM2.5.•Synergistic abatement of NH3 and NOX mitigates more PM2.5 than single reduction.