Influence of industrial emissions on volatile organic compound levels and secondary formation of organic aerosol and ozone in a multi-industrial city during the warm season

Abstract

In this study, we explored the spatial and temporal distributions of volatile organic compounds (VOCs) and their role in the formation of ozone (O3) and secondary organic aerosol (SOA). Both passive and active air sampling techniques were employed at 17 and 3 sites, respectively, during the warm season (May-August 2020) in Ulsan, the largest industrial city in South Korea. The total (Sigma 52) VOC levels at industrial sites (214 mu g/m3), particularly in petrochemical, automobile, and shipbuilding industrial complexes, were higher than at rural (50.2 mu g/m3) and urban (65.0 mu g/m3) sites during the passive sampling period, with no significant diurnal variation during the active sampling period. On the other hand, isoprene, a representative biogenic VOC, was observed at higher concentrations at the rural sites, particularly during the daytime under favorable meteorological conditions. Furthermore, potential impacts from industrial emissions of isoprene were identified. Non-traffic sources (industrial activities) were dominant in the study area, while the rural and urban sites were more affected by traffic and aged sources. Aromatic compounds, especially toluene, ethylbenzene, and m,p,o-xylenes, were significant contributors to both ozone formation potential (OFP) and SOA formation potential (SOAFP). In addition to aromatics, higher OFPs of n-octane and 3-methylpentane were also observed at the industrial sites. This study highlights the critical role of industrial complexes in determining the levels and spatial distribution of VOCs and their secondary products.