Comprehensive Characterization and Source Analysis of VOC Fluxes in a Chinese Megacity

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Urban Climatology

Background:

• Volatile organic compounds (VOCs) are crucial precursors to secondary air pollutants like ozone and PM2.5.
• Urban VOC emission patterns are complex due to diverse anthropogenic activities, challenging source identification.
• Understanding VOC origins is vital for mitigating urban air pollution and its health impacts.

Purpose of the Study:

• To investigate VOC sources and strengths in a Chinese megacity using eddy covariance flux measurements.
• To elucidate the role of chemical evolution in shaping urban VOC atmospheric composition.
• To compare source apportionment using VOC flux and concentration data.

Main Methods:

• Eddy covariance flux measurements of VOCs were performed in a Chinese megacity.
• Positive Matrix Factorization (PMF) was applied to both flux and concentration datasets for source apportionment.
• Compositional differences between VOC fluxes (emissions) and concentrations (processed air) were analyzed.

Main Results:

• Pronounced temporal and compositional differences were observed between VOC fluxes and concentrations.
• Flux-based source apportionment indicated toluene is primarily linked to volatile chemical products (VCPs), not traffic.
• Biogenic and anthropogenic contributions to monoterpene fluxes were quantified (53% vs. 47%), influenced by temperature.

Conclusions:

• Chemical evolution plays a critical role in the atmospheric composition of urban VOCs.
• Integrating VOC flux and concentration data enhances the understanding of urban emission sources and their atmospheric behavior.
• Flux measurements offer advantages for accurate VOC source apportionment in urban environments.