Enhancement of PM_2.5 source appointment in a large industrial city of Korea by applying the elemental carbon tracer method for positive matrix factorization (PMF) model

The concentration of particulate matter with an aerodynamic diameter less than 2.5 μm (PM_2.5) measured in an industrial area is strongly influenced by the industrial characteristics of the region. Ulsan, an industrial city in Korea, has a large regional impact on PM_2.5 concentration because various industries, such as the petrochemical, automobile manufacturing, and shipbuilding, are located in this city. As such, the PM_2.5 pollution sources must be identified to enable its management. In this study, PM_2.5 source apportionment was conducted in Ulsan. In this process, the contribution to secondary organic formation was estimated considering the secondary organic carbon (SOC) calculated using the elemental carbon (EC) tracer method. Sources were classified into ten categories (i.e., coal-related, industry, sea salt, secondary sulfate, soil, oil combustion, secondary nitrate, traffic-related, SOC formation, and primary emission). Of these, secondary formation contributed approximately 71%. The high rate of secondary production seems to be influenced by the industry in the area. Contributions of secondary sulfate and secondary nitrate were related to the seasons, contributing to the most, in summer and winter, respectively. SOC formation was highest in spring, not summer, which seems to be due to the decrease in organic carbon (OC) concentration due to the washing effect of summer. The contribution of secondary formation in Ulsan was likely overestimated due to the influence of local sources. The positive matrix factorization (PMF) with SOC performed in this study can help to easily separate the PM_2.5 sources of secondary formation and primary emissions.