Program

General Session 4: Marine environment, ecosystem & sustainability

Poster

Air-sea exchange and gas/particle partitioning of polycyclic aromatic hydrocarbons from the East China Sea to the Northwest Pacific: Assessment of influence of East Asian continental outflow
GS4-38-S
Zilan Wu* , Fudan University
Zhigang Guo, Fudan University
Presenter Email: 15110740013@fudan.edu.cn

The East Asian continental outflow was analyzed during a research cruise across a transect of the Northwest Pacific (NWP) in the spring of 2015 using 15 targeted parent polycyclic aromatic hydrocarbons (PAHs) as a tracer. We characterized the strong East Asian outflow by determining air-sea exchange and atmospheric partitioning of PAHs. The sum of 15 gas phase PAHs (3.62-13.62 ng m-3) were substantially higher than those in particle phase (0.17-0.55 ng m-3). The PAHs in atmosphere did not display a temperature-dependence and they were strongly correlated with the land-based long-range atmospheric transport as indicated by backward trajectories. The instantaneous total PAH air-sea exchange fluxes were estimated ranging from -89.20 to 72.41 ng m-2 d-1. Though most sites in the open ocean indicated a net volatilization, the gaseous PAHs in the overlying air were mainly supported by the upwind source regions rather than surface seawater. The net absorption occurred mostly in the offshore regions of East China Sea and PAHs were also found to deposit in some remote oceanic sites, suggesting the influence of continental outflow on the air-sea exchange. The long-range transported carbon-rich aerosols from upwind continent exerted a great effect on PAHs partitioning behavior over the NWP, as supported by the variations in log-log relationship between KP (gas/particle partition coefficients) and KOA (octanol/air partition coefficient) during the whole cruise. In addition, soot-included partitioning model yielded a better match particularly for medium molecular weight PAHs indicative of the importance of continentally-derived soot particles.