Maximizing ozone control by spatial sensitivity-oriented mitigation strategy in the Pearl River Delta Region, China

Runyu Wang; Lili Wang; Jiaren Sun; Lei Zhang; Yuanyuan Li; Ke Li; Boya Liu; Jiaxin Zhang; Yuesi Wang

doi:10.1016/j.scitotenv.2023.166987

Maximizing ozone control by spatial sensitivity-oriented mitigation strategy in the Pearl River Delta Region, China

Sci Total Environ. 2023 Dec 20:905:166987. doi: 10.1016/j.scitotenv.2023.166987. Epub 2023 Sep 17.

Authors

Runyu Wang¹, Lili Wang², Jiaren Sun³, Lei Zhang¹, Yuanyuan Li⁴, Ke Li⁵, Boya Liu¹, Jiaxin Zhang¹, Yuesi Wang¹

Affiliations

¹ State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China; College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
² State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. Electronic address: wll@mail.iap.ac.cn.
³ Guangdong Province Engineering Laboratory for Air Pollution Control, Guangdong Provincial Key Laboratory of Water and Air Pollution Control, South China Institute of Environmental Sciences, MEE, Guangzhou 510655, China. Electronic address: sunjiaren@scies.org.
⁴ Xinjiang Weather Modification Office, Urumqi 830002, China; Xinjiang Weather Modification Engineering Technology Research Center, Urumqi 830002, China.
⁵ 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 and Technology, Nanjing 210044, China.

PMID: 37717781
DOI: 10.1016/j.scitotenv.2023.166987

Abstract

The Pearl River Delta (PRD) has long been plagued by severe O₃ pollution, particularly during the autumn. A regional O₃ pollution episode influenced by the Western Pacific Subtropical High in September 2021 was characterized by near-surface O₃ escalation due to strong photochemical reactions within the planetary boundary layer. This event was targeted to develop effective control strategies through investigation of precursor control type and scope based on the high-order decoupled direct method (HDDM) and integrated source apportionment method (ISAM) of CMAQ. Generally, the majority of areas (67.0 %) were under NO_x-limited regime, which should strengthen afternoon NO_x control inferred by positive convex O₃ responses. However, high emission and heavily polluted areas located in central PRD were under VOC-limited regime (11.6 %) or mixed regime (15.0 %). The remaining areas (6.4 %) were under NO_x-titration or insensitive conditions. Regarding source apportionment, Guangdong province contributed 32.3 %-58.4 % to MDA8 O₃ of PRD, especially higher proportion (>50 %) to central areas. Overall, local-focused NO_x/VOC emission reductions had limited effects on O₃ mitigation for receptor cities compared to regional-cooperative regulation. When region-wide VOC emission reduction was implemented, MDA8 O₃ in VOC-limited grids exhibited the largest declines (2.3 %-4.1 %, 3.9- 7.0 μg·m^-3). However, unified NO_x control contributed to increasing MDA8 O₃ in VOC-limited grids (most stations located for air quality evaluation) whereas decreased MDA8 O₃ by 2.1 %- 5.7 %, 3.0- 8.2 μg·m^-3 in large-scale NO_x-limited grids. The sensitivity-oriented regional control avoided O₃ rebound and achieved the greatest decline of 3.4 %- 5.0 %, 5.7- 8.4 μg·m^-3 in VOC-limited grids; additionally, time-refined dynamic aggressive NO_x control decreased peak O₃ by an extra 1.2- 6 μg·m^-3, both of which facilitate the regulation for the forecasting O₃ episodes. These findings suggest that in heavily polluted environments, the enhancement of O₃ regulation benefits requires meticulous, coordinated, and dynamic NO_x and VOC controls spanning the entire region based on high-resolution analysis of heterogeneous O₃-NO_x-VOC sensitivity. Furthermore, emission reduction gains should be more reasonably reflected through increasing in-situ observations covering multi-sensitivity regions.

Keywords: Geography-differentiated collaborative control; HDDM; ISAM; O(3)-precursors sensitivity; Pearl River Delta.