Preprints
https://doi.org/10.5194/acp-2021-455
https://doi.org/10.5194/acp-2021-455

  27 Jul 2021

27 Jul 2021

Review status: this preprint is currently under review for the journal ACP.

Long-term trends and drivers of aerosol pH in eastern China

Min Zhou1,2, Guangjie Zheng3, Hongli Wang1, Liping Qiao1, Shuhui Zhu1, Dandan Huang1, Jingyu An1, Shengrong Lou1, Shikang Tao1, Qian Wang1, Rusha Yan1, Yingge Ma1, Changhong Chen1, Yafang Cheng3, Hang Su1,4, and Cheng Huang1 Min Zhou et al.
  • 1State Environmental Protection Key Laboratory of the Cause and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai 200233, China
  • 2School of Atmospheric Sciences, Nanjing University, Nanjing 210023, China
  • 3Minerva Research Group, Max Planck Institute for Chemistry, Mainz 55128, Germany
  • 4Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz 55128, Germany

Abstract. Aerosol acidity plays a key role in regulating the chemistry and toxicity of atmospheric aerosol particles. The trend of aerosol pH and its drivers are crucial in understanding the multiphase formation pathways of aerosols. Here, we reported the first trend analysis of aerosol pH from 2011 to 2019 in eastern China. The implementation of the Air Pollution Prevention and Control Action Plan leads to −35.8 %, −37.6 %, −9.6 %, −81.0 % and 1.2 % changes of PM2.5, SO42−, NHx, NVCs and NO3 in YRD during this period. Different from the fast changes of aerosol compositions due to the implementation of the Air Pollution Prevention and Control Action Plan, aerosol pH shows a moderate change of −0.24 unit over the 9 years. Besides the multiphase buffer effect, the opposite effects of SO42− and non-volatile cations changes play key roles in determining the moderate pH trend, contributing to a change of +0.38 and −0.35 unit, respectively. Seasonal variations in aerosol pH were mainly driven by the temperature, while the diurnal variations were driven by both temperature and relative humidity. In the future, SO2, NOx and NH3 emissions are expected to be further reduced by 86.9 %, 74.9 % and 41.7 % in 2050 according to the best health effect pollution control scenario (SSP1-26-BHE). The corresponding aerosol pH in eastern China is estimated to increase by ~0.9, resulting in 8 % more NO3 and 35 % less NH4+ partitioning/formation in the aerosol phase, which suggests a largely reduced benefit of NH3 and NOx emission control in mitigating haze pollution in eastern China.

Min Zhou et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-455', Anonymous Referee #1, 11 Aug 2021
  • RC2: 'Comment on acp-2021-455', Anonymous Referee #2, 22 Sep 2021

Min Zhou et al.

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Short summary
The trend of aerosol pH and its drivers are crucial in understanding the multiphase formation pathways of aerosols. Our work shows that the opposite effects of SO42− and non-volatile cations changes play key roles in determining the moderate pH trend. Future aerosol pH will increase slightly under strict control policy, resulting in more nitrate partitioning in aerosol phase, hence reducing the benefit of NH3 and NOx emission control in mitigating haze pollution in eastern China.
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