Seasonal Variability of Polycyclic Aromatic Hydrocarbons (PAHs) in a Coastal Marine Area in the Northwestern Region of the Sea of Japan/East Sea (Possiet Bay)

Abstract

Contamination by persistent organic pollutants including polycyclic aromatic hydrocarbons (PAHs) constitutes a major concern in relation to aquatic ecosystems. To study the seasonal variability of the vertical distribution of PAHs in Possiet Bay (the Sea of Japan/East Sea), surface and near-bottom water samples were collected in February, May, July and November 2013. In the surface layer, the total concentration of 13 PAHs ranges from 11 to 29.6 ng/L over the year with a peak in February. Near-bottom PAHs concentrations varied from 13 to 29.5 ng/L with a peak in May. Seasonal changes in the suspended particulate matter with sorbed PAHs (PPAHs) distribution were detected. Surface-bottom depletion of PPAHs was observed in winter. For spring and summer, the higher near-bottom PPAHs content in comparison with surface PPAHs is attributed to resuspension of particles with PAHs from the sediment in storm events. In autumn, there were similar PPAHs concentrations in the surface and near-bottom layers as a result of the strong mixing typical for the study area at that time. The PAHs isomer ratio indicates both petrogenic and pyrogenic PAHs sources in winter and spring, whereas in summer and autumn, PAHs are derived only from combustion. The partitioning of PAHs is also influenced by seasonality. These findings are useful for understanding the dynamics of PAHs pollution in a coastal marine area of the Sea of Japan (East Sea).