Enhanced validation and application of satellite-derived formaldehyde data for assessing photochemical pollution in the Chinese Greater Bay Area

Yiming Zhao; Jiangyong Li; Hao Wang; Daocheng Gong; Qinqin Li; Dakang Wang; Jinnian Wang; Boguang Wang

doi:10.1016/j.envpol.2024.125553

Enhanced validation and application of satellite-derived formaldehyde data for assessing photochemical pollution in the Chinese Greater Bay Area

Environ Pollut. 2024 Dec 17:366:125553. doi: 10.1016/j.envpol.2024.125553. Online ahead of print.

Authors

Yiming Zhao¹, Jiangyong Li¹, Hao Wang², Daocheng Gong³, Qinqin Li³, Dakang Wang⁴, Jinnian Wang⁴, Boguang Wang⁵

Affiliations

¹ College of Environment and Climate, Institute for Environmental and Climate Research, Jinan University, Guangzhou, 511443, China.
² College of Environment and Climate, Institute for Environmental and Climate Research, Jinan University, Guangzhou, 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, Guangzhou, 511443, China; Australia-China Centre for Air Quality Science and Management (Guangdong), Guangzhou, 511443, China. Electronic address: wanghao@jnu.edu.cn.
³ College of Environment and Climate, Institute for Environmental and Climate Research, Jinan University, Guangzhou, 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, Guangzhou, 511443, China.
⁴ Institute of Aerospace Remote Sensing Innovations (ARSI) Guangzhou University, Guangzhou, 510006, China; School of Geography and Remote Sensing, Guangzhou University, Guangzhou, 510006, China.
⁵ College of Environment and Climate, Institute for Environmental and Climate Research, Jinan University, Guangzhou, 511443, China; Guangdong Provincial Observation and Research Station for Atmospheric Environment and Carbon Neutrality in Nanling Forests, Guangzhou, 511443, China; Australia-China Centre for Air Quality Science and Management (Guangdong), Guangzhou, 511443, China.

PMID: 39701363
DOI: 10.1016/j.envpol.2024.125553

Abstract

Formaldehyde (HCHO) is a key player in photochemical processes and serves as a crucial precursor in the formation of hydroxyl radicals and ozone (O₃). While satellite observations can offer extensive spatiotemporal distributions of HCHO at both global and regional scales, the reliability of these satellite-derived HCHO measurements remains uncertain. In this study, we generated a five-year (June 2018-May 2023) Level 3 HCHO dataset, by applying spatial averaging technique to the TROPOspheric Monitoring Instrument (TROPOMI) Level 2 data. We validated this dataset against ground-based HCHO and O₃ measurements collected from 12 sites across the Greater Bay Area (GBA) in China, a region known for severe photochemical pollution. Our results indicated that the Level 3 HCHO dataset significantly outperforms the Level 2 HCHO data in representing the spatial distribution (r > 0.5) and temporal variation of surface HCHO. Moreover, Level 3 HCHO exhibited a stronger correlation (r > 0.65) with surface O₃ compared to surface HCHO, particularly during periods of intense photochemical pollution. With reduced interference from primary HCHO emissions at the surface, Level 3 HCHO offers a more accurate representation of photochemical pollution. Additionally, the combination of Level 3 HCHO, ground-based measurements, and model simulations highlighted the central GBA as a persistent hotspot for photochemical pollution. Further analysis identified anthropogenic volatile organic compounds, especially those emitted from solvent use, as key contributors to the formation of photochemical pollution in the region. This study provides a more reliable satellite-derived HCHO dataset for the GBA and offers critical insights into the spatiotemporal variability and mitigation of surface O₃ in this heavily polluted area.

Keywords: HCHO; Photochemical pollution; Spatiotemporal distribution; TROPOMI; WRF-CMAQ.