Air-sea Interface Process Of Polycyclic Aromatic Hydrocarbons From The North Pacific To The Western Arctic

Polycyclic Aromatic Hydrocarbons(PAHs)in the air and seawaters were collected during the 4th and 6th Chinese National Arctic Research Expedition.Distribution and sources of PAHs from the North Pacific to the Western Arctic,vertical profile in the Arctic,as well as air-sea interface process were discussed.The main conclusions are as followed:PAHs in the surface seawaters from the North Pacific Ocean to the Arctic Ocean,as well as a water column in the Arctic Ocean,were collected by active sampling during the 4th Chinese National Arctic Research Expedition in summer 2010.The total concentrations of the seven dissolved PAHs(?7PAH)in surface water ranged from 1.0 to 5.1 ng/L,decreasing with increasing latitude,and isomer pair ratios indicated that PAHs primarily descended from the mixed sources of petrogenic and pyrolytic origin.The vertical profile of PAHs in the Arctic Ocean was generally characteristic of surface enrichment and depth depletion,which emphasized the role of vertical water stratification and particles settling processes.Air-sea exchange fluxes suggested that PAHs are mostly undergoing net deposition in the North Pacific and the Arctic.PAHs in the air and surface seawaters from the North Pacific Ocean to the Arctic Ocean were collected by passive sampling during the 6th Chinese National Arctic Research Expedition in summer 2014.The total concentrations of the eleven freely-dissolved PAHs(?11PAH)in surface water ranged from 1.83 to 16.19 ng/L,decreasing with increasing latitude.Terrestrial input and ocean current LRT had significant influence on the horizontal distribution of seawater PAHs.The total concentrations of the nine gaseous PAHs(?9PAH)in air ranged from 0.67 to 12.55 ng/L,decreasing with increasing latitude.Volatilization from seawater and air mass transfer contributed most to the horizontal distribution of atmospheric PAHs.Isomer pair ratios indicated that PAHs primarily descended from the combustion sources.Air-sea exchange fluxes suggested that PAHs are mostly undergoing net volatilization from the North Pacific to the Western Arctic,which meant that the North Pacific and the Arctic serves as secondary sources for PAHs in summer.The air-sea exchange fluxes studied above were all based on the two-film model,which partition between dissolved and particulate phase,dry/wet deposition and degradation processes were neglected.In addition,the two-film model assumes that there is a stable film on both sides of the interface and the material is exchanged in a molecular diffusion mode,which is difficult in marine environment.In order to simulate the air-sea interface process of PAHs more accurately and comprehensively,the a:ir-sea interaction fugacity model of PAHs in the Bering Sea was established,according to the PAHs data sampled in 2010.The results indicated that the volatilization,absorption,rainwater dissolution,wet and dry deposition fluxes of?7PAH are 0.681,4.335,0.199,0.177 and 0.007 nmol/m2/d.The total deposition flux is bigger than the volatilization flux,which meant that the ocean serves as a sink for PAHs,at least in summer.The deposition and volatilization of acenaphthylene and acenaphthene almost reached equilibrium,and any perturbation,such as a rise in temperature,might lead to disequilibrium and remobilize these compounds from their Arctic reservoirs.Air-sea interface process research is the most direct and effective way to solve the "source sink" controversy of pollutants.And both of our results implied that whether the semivolatile organic compounds(SVOCs)was volatilizing or not was undergoing the process of transformation in the rapid climate change,and the fate of SVOCs needs further study.The following work of this sutdy will focus on the expansion of the study area and the richness of the fugacity model.