An intensive sampling program was conducted at two coastal sites of megacity Shanghai - the emerging town Lingang New Area (LGNA), and the chemical-industry zone Jinshan Area (JSA) from July, 2016 - June, 2017, to study the environmental behavior and fate of atmospheric polycyclic aromatic hydrocarbons (PAHs). The median concentrations of total atmospheric PAHs were 18 ng m -3 and 12 ng m -3 in JSA and LGNA, which were lower than those recently detected in northern coastal China, and previously detected in urban/suburban Shanghai, probably due to adjustment of energy consumption pattern. Almost 95% atmospheric PAHs were detected in gas phase, which was dominated by lighter 2-3 ring compounds, especially naphthalene and two methylnaphthalenes, in contrast to the particle phase PAHs, dominated by heavier 4-5 ring compounds. PAHs in gas and particle phase exhibited significant positive and negative correlations with temperature, indicating the importance of ongoing local volatilization, especially for petroleum related, coal and biomass combustion sources, although some were affected by marine air masses. The fraction of individual particle-bound PAHs, ranging from 0.24% to 54%, significantly related to their intrinsic physical-chemical properties, including octanol-air partition coefficient (K OA ) and subcooled liquid vapor pressure (P L ), while the fraction of particle-bound PAHs also changed dramatically with seasons, with higher contributions in winter than summer. Atmospheric PAHs would deposit to the coastal waters, with gaseous absorption fluxes almost an order of magnitude higher than those of particle-bound deposition
