Aircraft-based observation of volatile organic compounds (VOCs) over the North China Plain

Abstract. The vertical distribution of reactive trace gases can greatly help understand the complex atmospheric evolution under the joint impacts of surface emission, chemical removal, and regional transport. Focusing on the core area of the North China Plain, aircraft-based observations were conducted in September 2017 and July 2019 to reveal the vertical distributions of volatile organic compounds (VOCs) measured by high-time resolution mass spectrometry. Generally decreasing trends of VOC concentrations with altitudes were captured, indicating strong surface source emissions and chemical removal within the planetary boundary layer (PBL). Ethanol exhibited the highest concentration within the PBL with an average of 46.7 ppbv and the largest ratio (16.5) between the average below and above the PBL heights. The vertical-averaged VOCs above Baoding were greater than those in Beijing by factors ranging from 1.2 to 3.5, suggesting richer precursors for secondary pollutant formation in Baoding. Increases of several VOC species, including styrene and acetonitrile, at high altitudes (>2500 m) were captured in Beijing. Correlation analysis further revealed the significant influences of industrial and biomass burning emissions. Our results highlight the critical role of both local emissions and regional transport in shaping the VOC vertical distributions, which may affect atmospheric organic chemistry across various atmospheric layers in the region.