Secondary PM2.5 dominates aerosol pollution in the Yangtze River Delta region: Environmental and health effects of the Clean air Plan

Nan Li; Haoran Zhang; Shuhan Zhu; Hong Liao; Jianlin Hu; Keqin Tang; Weihang Feng; Ruhan Zhang; Chong Shi; Hongmei Xu; Lei Chen; Jiandong Li

doi:10.1016/j.envint.2022.107725

Secondary PM_2.5 dominates aerosol pollution in the Yangtze River Delta region: Environmental and health effects of the Clean air Plan

Environ Int. 2023 Jan:171:107725. doi: 10.1016/j.envint.2022.107725. Epub 2022 Dec 30.

Authors

Nan Li¹, Haoran Zhang¹, Shuhan Zhu¹, Hong Liao², Jianlin Hu¹, Keqin Tang¹, Weihang Feng³, Ruhan Zhang⁴, Chong Shi⁵, Hongmei Xu⁶, Lei Chen¹, Jiandong Li¹

Affiliations

¹ Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, 210044, China.
² Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, 210044, China. Electronic address: Hongliao@nuist.edu.cn.
³ Institute for Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, Helsinki, 00014, Finland.
⁴ Department of Environmental Science and Engineering, Fudan University, Shanghai, 200438, China.
⁵ Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, 100094, China.
⁶ Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an, 710049, China.

PMID: 36599225
DOI: 10.1016/j.envint.2022.107725

Abstract

The Clean Air Plan has been active in China since 2013 to mitigate severe PM_2.5 pollution. In this study, we applied the air quality model WRF-Chem to simulate PM_2.5 in the Yangtze River Delta (YRD) region of China in 2017, with the aim of assessing the air quality improvement and its associated health burden in the final year of the Clean Air Plan. To better describe the fate of various PM_2.5 compositions, we updated the chemical mechanisms in the model beforehand, including heterogeneous sulfate reactions, aqueous secondary organic aerosol (SOA) uptake, and volatility basis set (VBS) based SOA production. Both the observation and simulation results agreed that the stringent clear air action effectively reduced the PM_2.5 pollution levels by ∼ 30 %. The primary PM_2.5 (-6 ∼ - 16 % yr^-1) showed a more significant decreasing trend than the secondary PM_2.5 (-2 ∼ - 8 % yr^-1), which was mainly caused by the directivity of the clear air actions and the worsening ozone pollution in the recent years. The inconsistent decreasing trends of PM_2.5 components subsequently led to an increasing proportion of secondary PM_2.5. Nitrate particles, higher in the central and western YRD region, have replaced sulfate and have become the largest component of secondary inorganic aerosols year-round, except in summer, when strong ammonium nitrate evaporation occurs. In addition, SOA remains an important component (21 ∼ 22 %) especially in summer, most of which is produced from the oxidation and ageing of semi/intermediate volatile organic compounds (S/IVOC). Furthermore, we quantified the associated health impacts and found that the Clean Air Plan has largely reduced premature mortality due to PM_2.5 exposure in the YRD region from 399.1 thousand to 295.7 thousand. Our study highlights the benefits of the Clean Air Plan and suggests that subsequent PM_2.5 improvement should be geared more towards controlling secondary pollutants.

Keywords: Emission control; PM(2.5) pollution; Premature mortality; WRF-Chem; YRD.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aerosols / analysis
Air Pollutants* / analysis
Air Pollution*
China
Environmental Monitoring
Particulate Matter / analysis
Seasons
Sulfates / analysis

Substances

Air Pollutants
Particulate Matter
Aerosols
Sulfates