Seasonal variation, phase distribution, and source identification of atmospheric polycyclic aromatic hydrocarbons at a semi-rural site in Ulsan, South Korea.

Polycyclic aromatic hydrocarbons (PAHs) in gaseous and particulate phases (n = 188) were collected in Ulsan, South Korea, over a period of one year (June 2013‒May 2014) to understand the seasonal variation and phase distribution of PAHs as well as to identify the seasonal PAH emission sources. The target compounds were the 16 US-EPA priority PAHs, with the exception of naphthalene, acenaphthylene, and acenaphthene. Winter and spring had the highest and lowest PAH concentrations, respectively. The mean of the Σ PAHs in the gaseous phase (4.11 ng/m) was higher than that in the particulate phase (2.55 ng/m). Fractions of the gaseous or 3- and 4-ring PAHs (i.e., Flu, Phe, and Ant) were high in summer, and those of the particulate or 5- and 6-ring PAHs (i.e., BkF, BaP, Ind, DahA, and BghiP) increased in winter. Gas/particle partitioning models also demonstrated the increased contributions of the particulate PAHs in spring and winter. Source identification of PAHs was undertaken using diagnostic ratios, principal component analysis, and positive matrix factorization. The results indicated that pyrogenic sources (e.g., coal combustion) were dominant in winter. Other types of pyrogenic (e.g., industrial fuel combustion) and petrogenic sources were the main PAH sources in summer and autumn. The influence of both sources, especially in summer, might be due to seasonal winds transporting PAHs from the industrial areas. Two types of pyrogenic sources, diesel and coal combustion, were identified as the main PAH sources in spring. This study clearly demonstrates a source-receptor relation of PAHs at a semi-rural site in a heavily industrialized city.