Characterization of polycyclic aromatic hydrocarbons in concurrently monitored surface seawater and sediment along Dalian coast after oil spill.

Polycyclic aromatic hydrocarbons (PAHs) were measured in concurrently sampled surface seawater and sediment collected at 20 sites around Dalian, China 50 days after an oil spill accident. The concentrations of total PAHs ranged from 15 to 160 ng L(-1) in seawater, and from 64 to 2100 ng g(-1) dry weight in surface sediment. The spatial trends of PAHs in seawater, but not in sediment, showed a significant negative correlation with the distance from the oil spill site, indicating a strong source of PAHs from oil spill place to the surrounding seawater. The similar profiles for PAH composition in both crude oil and seawater could indicate that oil spill caused PAHs concentration in seawater, but not in sediment. Analysis of water-sediment exchange of PAHs showed that the direction of the net flux of PAHs was from sediment to seawater for most priority PAHs, and from water to sediment for a few HWM-PAHs.