夏季长江口及其邻近海域海水及大气中挥发性卤代烃的分布与海-气通量研究

Volatile halocarbons (VHCs) are important atmosphere trace gases, which play significant roles in the global warming and atmospheric chemistry. The concentrations of six VHCs including CFC-11, CFC-12, CH₂Cl₂, CCl₄, C₂Cl₄ and CHBr₃ in the seawater of the Yangtze River Estuary and adjacent area were determined by purge and trap-chromatography during the period of 4-16 July 2016. Furthermore, CCl₄, CFC-11, CFC-12 and C₂Cl₄ concentrations in the marine atmosphere were determined. The results showed that the concentrations of six VHCs in the coastal waters were higher than those in the open sea, due to the impact of terrestrial input, water mass and biological production. Influenced by geographical position and hydrological conditions, the concentrations of six VHCs were different in the vertical distributions, although they had a common feature with the maxima appearing in the 0~20 meters of sea water. Significant positive correlations were observed among the CCl₄, C₂Cl₄ and CFC-11 concentrations, suggesting that they might have some common sources. Besides, a positive correlation was found between the CHBr₃ and chlorophyll a (Chl-a) concentrations in the surface seawater, indicating that phytoplankton biomass might play an important role in controlling the distribution of CHBr₃ in the study area. No correlation was observed between the CHBr₃ and pH. The atmospheric concentrations of CCl₄, CFC-12 and C₂Cl₄ in the study area were higher than the global averages except CFC-11. According to the analytical results of backward trajectories, the atmospheric diffusion and transport of the nearshore terrigenous pollutants were the main source of CCl₄, CFC-11 and CFC-12. The sea-to-air flux data indicated that the Yangtze River and adjacent area acted as a source for atmospheric CCl₄, C₂Cl₄, CHBr₃ and CH₂Cl₂ during the study period.