Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume 56, Issue 12, Pages 7608-7617Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.1c08346
Keywords
Orbitrap; mass spectrometry; positive matrix factorization (PMF); urban air pollution
Categories
Funding
- Research and Innovation Staff Exchange EU [69089]
- French National program LEFE (Les Enveloppes Fluides et l'Environnement)
- European Research Council [852161]
- European Research Council (ERC) [852161] Funding Source: European Research Council (ERC)
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This study conducted a comprehensive campaign in Shanghai and used a chemical ionization-Orbitrap mass spectrometer to identify the major gas-phase oxidation processes leading to the formation of oxygenated organic molecules (OOM). The study highlights the importance of a stricter multi-pollutant coordinated strategy in primary and secondary pollution mitigation.
Secondary organic aerosol, formed through atmospheric oxidation processes, plays an important role in affecting climate and human health. In this study, we conducted a comprehensive campaign in the megacity of Shanghai during the 2019 International Import Expo (EXPO), with the first deployment of a chemical ionization-Orbitrap mass spectrometer for ambient measurements. With the ultrahigh mass resolving power of the Orbitrap mass analyzer (up to 140,000 Th/Th) and capability in dealing with massive spectral data sets by positive matrix factorization, we were able to identify the major gas-phase oxidation processes leading to the formation of oxygenated organic molecules (OOM) in Shanghai. Nine main factors from three independent sub-range analysis were identified. More than 90% of OOM are of anthropogenic origin and >60% are nitrogen-containing molecules, mainly dominated by the RO2 + NO and/or NO3 chemistry. The emission control during the EXPO showed that even though the restriction was effectual in significantly lowering the primary pollutants (20-70% decrease), the secondary oxidation products responded less effectively (14% decrease), or even increased (50 to >200%) due to the enhancement of ozone and the lowered condensation sink, indicating the importance of a stricter multi-pollutant coordinated strategy in primary and secondary pollution mitigation.
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