Diurnal and seasonal variations of VOCs, and their contributions to cancer risks and secondary organic aerosol in the atmosphere of Seoul, South Korea

Abstract

Volatile organic compounds (VOCs) have various harmful effects on human health as well as the environment. Especially, benzene is classified as a carcinogenic compound, and toluene and xylenes are one of the compounds that have a larger potential to the formation of ozone (O3) and secondary organic aerosol (SOA) in the atmosphere. However, studies on the monitoring of atmospheric VOCs in Seoul have rarely been conducted. In this study, the sequential tube sampler (STS-25, Perkin Elmer) with adsorbent tubes (Carbotrap 300, Supleco) and a pump (MP-∑30KNⅡ, Sibata) was used to automatically collect 24 samples for a day every month from July 2018–June 2019 at an urban site in Seoul. The collected samples were analyzed using a thermal desorption-gas chromatograph/mass spectrometer (TD-GC/MS, Agilent), and the target compounds are 65 VOCs of US EPA TO-15. Among the target compounds, toluene, ethylbenzene, and m,p-xylenes were dominant, and the mean concentration of total VOCs was higher at rush hour (8:00 and 18:00 h) than the others. The level of seasonal concentrations was the highest in spring followed by those in summer, winter, and fall, however, there is not statistically different. Diagnostic ratios and conditional bivariate probability function (CBPF) were used to investigate the main sources of VOCs in Seoul, which seems to be more influenced by the local effects. In addition, the possibility of the long-range transport effect was identified with the monthly results of the HYSPLIT trajectory model. Then, the contributions of SOA formation and probabilistic distributions of carcinogenic and non-carcinogenic risks were estimated from fractional aerosol coefficient (FAC) and Monte-Carlo simulation, respectively. Finally, the periods having the highest SOA formation and risks to human health were identified.