Transboundary movement of polycyclic aromatic hydrocarbons (PAHs) in the Kuroshio Sphere of the western Pacific Ocean

Atmospheric PAHs in the Kuroshio Sphere of southern Taiwan were measured and characterized using samples collected simultaneously at four sites from February to October in 2007. Higher PAH concentrations occurred in winter (range 2.41 ± 1.85 to 40.8 ± 6.97 ng m−3) and autumn (range 1.21 ± 0.32 to 65.1 ± 57.4 ng m−3) than in summer (range 0.87 ± 0.36 to 17.7 ± 2.88 ng m−3). Comparison of the total PAH concentrations from the four sampling sites showed that the total PAH concentrations from the Kaohsiung urban site (KHU) were 1.7–4.4 times higher than those from the Kaohsiung coastal site (KHC), 3.6–26 times those from a rural coastal site (Kenting, KT), and 16.9–53.8 times those from an offshore island site (Lanyu, LY). The PAH compositional pattern, diagnostic ratios and principal component analysis indicated that the major sources of PAHs in the study area can be classified into three categories. The first is vehicular sources from local traffic, the second is natural soils, and the third is industrial activities including coke ovens and incinerator emissions. The results from back trajectories also demonstrated that atmospheric PAHs were produced by local sources but were also influenced by transboundary movement of terrestrial pollutants. The characteristics and sources of atmospheric PAHs identified in this study provide useful information for estimating the effects and transportation of PAHs in the Kuroshio Sphere.

► The concentrations of PAHs in the winter and autumn were much higher than those in summer.
► Distinct sources of the study area in different seasons were identified.
► The major sources of PAHs in the study area can be characterized as traffic, natural soils, and industrial activities.
► Polluted air from southwestern Taiwan might contribute significantly to the Kuroshio main stream.
► An event of a transboundary movement of PAHs was illustrated by back trajectories, fingerprinting and PCA.