Characteristics of volatile organic compounds in the metropolitan city of Seoul, South Korea: Diurnal variation, source identification, secondary formation of organic aerosol, and health risk

Atmospheric volatile organic compounds (VOCs) in Seoul, the capital of South Korea, have attracted increased attention owing to their emission, secondary formation, and human health risk. In this study, we collected 24 hourly samples once a month at an urban site in Seoul for a year (a total of 288 samples) using a sequential tube sampler. Analysis results revealed that toluene (9.08 ± 8.99 μg/m3) exhibited the highest annual mean concentration, followed by ethyl acetate (5.55 ± 9.09 μg/m3), m,p-xylenes (2.79 ± 4.57 μg/m3), benzene (2.37 ± 1.55 μg/m3), ethylbenzene (1.81 ± 2.27 μg/m3), and o-xylene (0.91 ± 1.47 μg/m3), indicating that these compounds accounted for 77.8–85.6% of the seasonal mean concentrations of the total (Σ59) VOCs. The concentrations of the Σ59 VOCs were statistically higher in spring and winter than in summer and fall because of meteorological conditions, and the concentrations of individual VOCs were higher during the daytime than nighttime owing to higher human activities during the daytime. The conditional bivariate probability function and concentration weighted trajectory analysis results suggested that domestic effects (e.g., vehicular exhaust and solvents) exhibited a dominant effect on the presence of VOCs in Seoul, as well as long-range atmospheric transport of VOCs. Further, the most important secondary organic aerosol formation potential (SOAFP) compounds included benzene, toluene, ethylbenzene, and m,p,o-xylenes, and the total SOAFP of nine VOCs accounted for 5–29% of the seasonal mean PM2.5 concentrations. The cancer and non-cancer risks of the selected VOCs were below the tolerable (1 × 10−4) and acceptable (Hazard quotient: HQ < 1) levels, respectively. Overall, this study highlighted the feasibility of the sequential sampling of VOCs and hybrid receptor modeling to further understand the source–receptor relationship of VOCs. [Display omitted] •Twenty four hourly air samples were collected once a month in Seoul, Korea.•BTEX and ethyl acetate were the most abundant compounds in each season.•Concentrations of VOCs were higher during daytime in spring and winter.•Domestic effects (vehicle and solvent) were dominant, and LRAT was also confirmed.•From the perspective of SOAFP and risk, BTEX were the most important compounds.