Temporal and vertical variations of polycyclic aromatic hydrocarbon at low elevations in an industrial city of southern Taiwan

Considered that human activities mostly occur below building heights, the objective of this study was to investigate the temporal variations of fine particular matter (PM(2.5))-associated polycyclic aromatic hydrocarbons (PAHs) and benzo[a]pyrene-equivalent (BaP(eq)) concentrations at four different elevations (6.1, 12.4, 18.4, and 27.1 m) in Kaohsiung City, the largest industrial city of southern Taiwan. Temperature variation was critical for the PM(2.5)-associated PAH concentrations, which were dominated by benzo[g,h,i]perylene (0.27 ± 0.04 ng m(−3) and 24.43% of the total concentration) and other high molecular weight (HMW) species. The PM(2.5)-associated BaP(eq) was dominated by 5-ring PAH (36.09%). The PM(2.5)-associated PAH and BaP(eq) concentrations at all elevations were significantly increased in winter. In the night, the correlations between the PM(2.5)-associated PAH concentrations and atmospheric temperatures became negatively stronger, notably at lower elevations (r = − 0.73 ~ − 0.86), whereas the BaP(eq) during daytime and nighttime were not changed significantly in most months. The PAHs analysis with different PM sizes demonstrated the importance of smaller particles such as PM(2.5). The meteorological variation was more important than elevation to influence the low-elevation PM(2.5)-associated PAH and BaP(eq) concentrations in an urban area like Kaohsiung City, as the two concentrations were dominated by the PAHs with HMWs and those 5-ring species, respectively.