Traditional studies on the occurrence, transport behavior and potential ecological risk of aromatic organic compounds (AOCs) often focus on the 16-priority controlled polycyclic aromatic hydrocarbons (PAHs) proposed by the United States Environmental Protection Agency (EPA) in the last century. However, more and more studies have shown that AOCs have stronger toxic effects compared with priority-controlled PAHs. In view of the complexity of AOCs molecular composition in environmental media, this study relies on comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOFMS) with stronger chromatographic separation capability to screen and initially establish a high-throughput database of AOCs molecular composition in offshore seawater in China. The composition characteristics, spatial distribution, potential aquatic ecological risks and their seasonal differences of AOCs in the Bohai Sea and the Yellow Sea were studied. By analyzing the GC×GC-TOFMS spectra of organic extracts from seawater, it was found that AOCs accounted for more than 50% of semi-volatile organic molecules in the surface water of the
Bohai Sea and the Yellow Sea. The 79 AOCs showed the highest concentration in autumn, followed by spring, and the lowest concentration in summer. The average total concentration was 2238±86 ng/L, 1266±486 ng/L and 1064±826 ng/L, respectively. In terms of spatial distribution, the concentrations of AOCs in the surface waters of Bohai Bay is significantly higher than that in the Yellow Sea. The spatial and temporal heterogeneity of AOCs is regulated by the intensity of land-based input and the drive of sea circulation. The potential aquatic ecological risk of AOCs was further evaluated based on hazard quotient (HQs) and Benzo[a]pyrene equivalent risk (BaPE) models respectively. The evaluation results showed that the aquatic ecological risk was significantly increased when 79 AOCs were included in the evaluation model compared to the parent PAHs. The molecular identification of AOCs and the high-throughput database established in this study are of reference significance for understanding the potential ecological impacts of AOCs emitted by human activities.

aromatic organic compounds,monitoring list,Bohai and Yellow Seas,surface seawater,spatial and temporal distribution,ecological risk