Investigation of priority anthropogenic VOCs in the large industrial city of Ulsan, South Korea, focusing on their levels, risks, and secondary formation potential

Abstract

Volatile organic compounds (VOCs) are a concern due to their human health risks and secondary reactions, which vary according to the physicochemical properties and photochemical reactivity of individual VOCs. In this study, 59 VOCs were monitored using passive air samplers at 5 industrial and 16 urban sites in Ulsan, the largest industrial city in South Korea, over the course of a week (July 28-August 4, 2021). During the sampling period, toluene (4.6 mu g/m3), ethylbenzene (3.2 mu g/m3), and m,p,o-xylenes (8.5 mu g/m3) accounted for 56.9% of the total (E59) VOCs. Elevated concentrations of E59 VOCs were observed in the automobile and shipbuilding industrial complexes, as well as at urban sites near the industrial complexes, due to dominant southeasterly winds. Toluene/benzene ratios indicated that fuel evaporation and solvent use were dominant during this warm sampling period. Benzene and naphthalene exhibited the highest mean cancer and non-cancer risks, respectively; however, none of the risks exceeded the US EPA's tolerable and acceptable safety levels. Furthermore, secondary organic aerosol formation potentials (SOAFPs) of VOCs were estimated, with toluene contributing the most. Additionally, explainable artificial intelligence analysis suggested that styrene was closely related to PM2.5 formation. Finally, priority lists of the top 10 VOCs based on their concentrations, risks, and SOAFPs were created, and aromatic compounds were frequently found on the lists. Based on these findings, customized management strategies for VOC reduction are recommended in multi-industrial cities.