Polycyclic aromatic hydrocarbons in surface seawater at the southern Okhotsk Sea, 2017-2022.

At the southern Okhotsk Sea over 352,000 tons of scallop, crab, salmon, and other major fish species are caught annually. However, polycyclic aromatic hydrocarbons (PAHs), with carcinogenic and/or mutagenic potential, are known to have high concentrations in the northern area off Sakhalin Island, where oil and natural gas are extracted and from where the nearshore East Sakhalin Current (ESC) begins running until the southern Okhotsk Sea during autumn-winter. From summer 2017 to winter 2022 the impact of ocean currents on PAHs migration around the southern Okhotsk Sea was studied. Two main areas (coastal and offshore) were identified in the southern Okhotsk Sea based on salinity, temperature, and radiotracers. The maximum Σ13PAHdiss was 5.1 ng L-1, recorded in the Japan Sea. Σ13PAHpart was the highest in winter, reaching over 10.0 ng L-1 in seawater and 65.1 ng L-1 in sea ice. The main sources of dissolved PAHs were pyrogenic, diesel, or gasoline engine emissions, as estimated from the isomeric ratios and PCA analysis. The main sources of particulate PAHs differed among the Japan Sea, the coastal area, and the offshore area, as well as among seasons. The highest percentage of PAHs was found in the dissolved phase. Nevertheless, in areas of the southern Okhotsk Sea with high primary productivity, marine particles might play an important role in the co-scavenging of organic pollutants.