Seasonal variations in marine polycyclic aromatic hydrocarbons off Oki Island, Sea of Japan, during 2015–2019

Abstract

Concentrations of 13 phase-partitioned polycyclic aromatic hydrocarbons (PAHs) in seawater were monitored monthly off Oki Island, Japan, during 2015–2019 to elucidate seasonal variations, main source, and transport pathways of PAHs in the southwestern Sea of Japan. Total PAH (dissolved plus particulate) concentrations in surface seawater at 36°09.0′N, 133°17.3′E (site OK) were in the range 0.49–9.36 ng L−1 (mean 2.77, SD 2.05 ng L−1) with higher levels in summer–autumn, an order of magnitude lower than those in the East China Sea during 2005 and 2009–2011 and about one-third of those recorded in the Sea of Japan in 2008 and 2010. The main sources of dissolved and particulate PAHs were combustion products. Increasing dissolved PAH levels during July–October indicate that the area around southern Oki Island is impacted by PAH-rich summer continental-shelf water transported by the Tsushima Warm Current flowing from the East China Sea.