TY - JOUR
T1 - Trends in secondary inorganic aerosol pollution in China and its responses to emission controls of precursors in wintertime
AU - Meng, Fanlei
AU - Zhang, Yibo
AU - Kang, Jiahui
AU - Heal, Mathew R.
AU - Reis, Stefan
AU - Wang, Mengru
AU - Liu, Lei
AU - Wang, Kai
AU - Yu, Shaocai
AU - Li, Pengfei
AU - Wei, Jing
AU - Hou, Yong
AU - Zhang, Ying
AU - Liu, Xuejun
AU - Cui, Zhenling
AU - Xu, Wen
AU - Zhang, Fusuo
PY - 2022/5/16
Y1 - 2022/5/16
N2 - The Chinese government recently proposed ammonia (NH3) emission reductions (but without a specific national target) as a strategic option to mitigate fine particulate matter (PM2.5) pollution. We combined a meta-analysis of nationwide measurements and air quality modeling to identify efficiency gains by striking a balance between controlling NH3 and acid gas (SO2 and NOx) emissions. We found that PM2.5 concentrations decreased from 2000 to 2019, but annual mean PM2.5 concentrations still exceeded 35 μgm-3 at 74% of 1498 monitoring sites during 2015-2019. The concentration of PM2.5 and its components were significantly higher (16 %-195 %) on hazy days than on non-hazy days. Compared with mean values of other components, this difference was more significant for the secondary inorganic ions SO2-4, NO-3, and NHC4+ (average increase 98 %). While sulfate concentrations significantly decreased over this period, no significant change was observed for nitrate and ammonium concentrations. Model simulations indicate that the effectiveness of a 50% NH3 emission reduction for controlling secondary inorganic aerosol (SIA) concentrations decreased from 2010 to 2017 in four megacity clusters of eastern China, simulated for the month of January under fixed meteorological conditions (2010). Although the effectiveness further declined in 2020 for simulations including the natural experiment of substantial reductions in acid gas emissions during the COVID-19 pandemic, the resulting reductions in SIA concentrations were on average 20.8% lower than those in 2017. In addition, the reduction in SIA concentrations in 2017 was greater for 50% acid gas reductions than for the 50% NH3 emission reductions. Our findings indicate that persistent secondary inorganic aerosol pollution in China is limited by emissions of acid gases, while an additional control of NH3 emissions would become more important as reductions of SO2 and NOx emissions progress.
AB - The Chinese government recently proposed ammonia (NH3) emission reductions (but without a specific national target) as a strategic option to mitigate fine particulate matter (PM2.5) pollution. We combined a meta-analysis of nationwide measurements and air quality modeling to identify efficiency gains by striking a balance between controlling NH3 and acid gas (SO2 and NOx) emissions. We found that PM2.5 concentrations decreased from 2000 to 2019, but annual mean PM2.5 concentrations still exceeded 35 μgm-3 at 74% of 1498 monitoring sites during 2015-2019. The concentration of PM2.5 and its components were significantly higher (16 %-195 %) on hazy days than on non-hazy days. Compared with mean values of other components, this difference was more significant for the secondary inorganic ions SO2-4, NO-3, and NHC4+ (average increase 98 %). While sulfate concentrations significantly decreased over this period, no significant change was observed for nitrate and ammonium concentrations. Model simulations indicate that the effectiveness of a 50% NH3 emission reduction for controlling secondary inorganic aerosol (SIA) concentrations decreased from 2010 to 2017 in four megacity clusters of eastern China, simulated for the month of January under fixed meteorological conditions (2010). Although the effectiveness further declined in 2020 for simulations including the natural experiment of substantial reductions in acid gas emissions during the COVID-19 pandemic, the resulting reductions in SIA concentrations were on average 20.8% lower than those in 2017. In addition, the reduction in SIA concentrations in 2017 was greater for 50% acid gas reductions than for the 50% NH3 emission reductions. Our findings indicate that persistent secondary inorganic aerosol pollution in China is limited by emissions of acid gases, while an additional control of NH3 emissions would become more important as reductions of SO2 and NOx emissions progress.
U2 - 10.5194/acp-22-6291-2022
DO - 10.5194/acp-22-6291-2022
M3 - Article
AN - SCOPUS:85130498852
SN - 1680-7316
VL - 22
SP - 6291
EP - 6308
JO - Atmospheric Chemistry and Physics
JF - Atmospheric Chemistry and Physics
IS - 9
ER -