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 0.49-9.36â¯ngâ¯L-1 (mean 2.77, SD 2.05â¯ngâ¯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.
Subject(s)
Polycyclic Aromatic Hydrocarbons , Water Pollutants, Chemical , China , Coal , Environmental Monitoring , Japan , Polycyclic Aromatic Hydrocarbons/analysis , Seasons , Water Pollutants, Chemical/analysisABSTRACT
The spatial variations of low-level 134Cs concentrations (activities) in seawater off the Japanese Archipelago, particularly in the eastern East China Sea (ECS), in 2018 and 2019 were examined. The 134Cs concentrations, decay-corrected to the date of the Fukushima Dai-ichi Nuclear Power Plant accident, in seawaters were 0.5-2.0 mBq/L. High 134Cs concentrations (1.1-2.0 mBq/L) of the Kuroshio Current subsurface water (densities of 25-26σθ) in the eastern ECS could indicated the contribution of the subtropical mode water from the Pacific Ocean side, and total column inventories were 330-426 Bq/m2. In contrast, as indicated by the same 134Cs concentration level at the surface of the eastern ECS and Sea of Japan, larger portions of the subsurface waters remained in the ECS and Yellow Sea side in response to the existence of the shallow Tsushima Strait.
