Key Takeaways & Executive Findings
- •• • Hainan's O3 pollution peaks in autumn and winter, while the Pearl River Delta (PRD) shows year-round O3 pollution, establishing PRD as the core control area for O3 in the three provinces. • • Haikou's O3 and PM2.5 concentrations exhibit strong correlations with Zhanjiang and Maoming throughout the year, with correlations intensifying in winter, indicating significant regional transport linkages. • • WPSCF analysis reveals that O3 pollution in Haikou is more dependent on stable cross-regional precursor transport and intense photochemical conditions, whereas PM2.5 transport pathways vary seasonally, with autumn driven by stable northeasterly winds and uniform pressure fields. • • Lag effect analysis confirms that pollution exceedance days are substantially influenced by upwind transport from the previous day, highlighting the dominant role of cross-regional physical transport in driving pollution episodes.
Abstract
Haikou, a representative tropical city in China, experiences air pollution influenced by both local emissions and regional transport. This study analyzed O3 and PM2.5 concentrations, emission sources, and meteorological fields from Haikou and Guangdong-Guangxi cities in 2024, employing correlation analysis and the Weighted Potential Source Contribution Function (WPSCF) to systematically investigate spatial-temporal patterns, regional linkages, and transport mechanisms. Results revealed distinct pollution characteristics: Hainan exhibited prominent O3 pollution in autumn and winter, while the Pearl River Delta (PRD) in Guangdong suffered significant O3 pollution year-round, positioning it as the core control area. Guangxi was characterized by severe PM2.5 pollution in winter with extensive high concentration areas. Haikou's O3 and PM2.5 concentrations showed strong correlations with those in Zhanjiang and Maoming throughout the year, particularly in winter. Regional transport analysis indicated that O3 pollution in Haikou depended on stable cross-regional precursor transport coupled with intense photochemical conditions, whereas PM2.5 exhibited diverse transport pathways across seasons. Lag effect analysis confirmed that pollution exceedance days were substantially influenced by upwind transport from the previous day, highlighting the dominant role of cross-regional physical transport. Autumn pollution was driven by stable surface northeasterly winds and upper-level uniform pressure fields. Potential source areas were highly consistent with the MEIC emission inventory, confirming distinct contributions of transport pathways for O3 and PM2.5. These findings provide a scientific basis for differentiated collaborative control of air pollution in tropical coastal cities.
1. Introduction
Regional air pollution transport poses a critical challenge for tropical coastal cities like Haikou, where local emissions alone cannot account for observed pollution episodes. Existing studies have documented the influence of regional transport on PM2.5 and O3 in various Chinese regions, but the specific pathways and mechanisms linking Haikou to the industrialized Guangdong-Guangxi provinces remain inadequately quantified. This gap hinders the development of effective joint prevention and control strategies tailored to tropical environments.
This study addresses this bottleneck by integrating 2024 observational data, emission inventories, and meteorological fields with correlation analysis and the Weighted Potential Source Contribution Function (WPSCF). By systematically analyzing the spatial-temporal patterns and transport correlations between Haikou and Guangdong-Guangxi cities, we identify key source regions and meteorological drivers. The findings provide actionable insights for differentiated regional air quality management, enabling targeted interventions in source areas and informed policy decisions for tropical coastal cities.
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SHENG Hui, MENG Xinxin, PI Dongqin, FU Yang, MAI Xiuqi, ZENG Yurong, XU Wenshuai (2026). Investigating the Transport Correlation of Ozone and PM2.5 between Haikou and Guangdong-Guangxi Cities. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2026051001
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Frequently Asked Questions
What are the dominant transport pathways for O3 and PM2.5 affecting Haikou, and how do they vary seasonally?
O3 pollution in Haikou is primarily driven by stable cross-regional precursor transport from Guangdong coastal cities, especially during autumn and winter, coupled with intense photochemical conditions. PM2.5 exhibits more diverse pathways, with winter transport from Guangxi and Guangdong, while autumn transport is influenced by stable northeasterly winds and uniform pressure fields, as indicated by WPSCF analysis.
How strong are the correlations between Haikou's pollutant concentrations and those of specific Guangdong-Guangxi cities?
Haikou shows strong year-round correlations with Zhanjiang and Maoming for both O3 and PM2.5, with correlations intensifying in winter. For O3, strong correlations also exist with other Guangdong coastal cities, indicating consistent regional transport patterns.
What meteorological conditions drive autumn pollution episodes in Haikou?
Autumn pollution episodes are driven by stable surface northeasterly winds and upper-level uniform pressure fields, which facilitate the transport of pollutants from upwind regions. These conditions align with the identified potential source areas and MEIC emission inventory, confirming the role of regional transport.
How does the lag effect analysis support the role of regional transport in pollution exceedance days?
Lag effect analysis shows that pollution exceedance days in Haikou are substantially influenced by upwind transport from the previous day, with a one-day lag. This temporal relationship underscores the dominant role of cross-regional physical transport over local photochemical production.
What are the implications of these findings for regional air pollution control strategies?
The distinct transport pathways for O3 and PM2.5 necessitate differentiated control measures. For O3, reducing precursor emissions in Guangdong coastal cities, particularly during autumn and winter, is critical. For PM2.5, controls should target winter emissions in Guangxi and Guangdong, while also considering seasonal meteorological conditions. Collaborative efforts across provinces are essential for effective mitigation.
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