资源环境科技发展态势分析平台

The vertical structure of volatile organic compounds (VOCs) is important to understanding the formation mechanisms of O-3 and secondary organic aerosol (SOA). To explore the vertical evolution characteristics of VOCs, an observational field campaign using a tethered balloon was carried out in Yuanshi County, Shijiazhuang, from January 8 to 16, 2019. Meteorological variables of the planetary boundary layer (PBL) were measured, and 83 VOC samples were collected. The concentrations of 87 compounds and a total of 10 vertical profiles were obtained. The VOC concentration gradually decreased from the surface to 1000 m, decreasing by 34.8% from the surface to 400 m and 11.4% from 400 m to 1000 m. The proportion of alkanes increased from 60.2% to 79.0%; the proportions of alkenes, halohydrocarbons, and acetylene decreased from 11.8%, 12.3%, and 4.2% to 4.5%, 2.8%, and 1.8%, respectively; and the proportion of aromatics changed very little. The vertical evolution of VOCs had responses to different meteorological conditions in the PBL. The concentration decreased slower in a strong convection state than in a stable state. The VOC concentration at night was higher in the stable boundary layer (SBL) (235 +/- 135 ppbv) than in the residual layer (RL) (181 +/- 135 ppbv). The concentration and NO3 loss rate of alkenes decreased in the RL at night, implying that the nighttime SOA formation potential may be weaker in the RL.