[Distribution characteristics and sea-air fluxes of volatile halocarbons in the East China Sea in winter].

Volatile halocarbons (VHCs) are important greenhouse gases, which play significant roles in the global warming and the chemistry of the atmosphere. The concentrations of four kinds of volatile halocarbons including CHCl3, C2 HCl3, C2 Cl4 and CHBr3 in seawater were determined by Purge and Trap-Chromatography in the East China Sea during the period of 23 December 2009-5 January 2010, and the sources of the VHCs were studied. The result showed that the means (ranges) of the CHCl3, C2 HCl3, C2 Cl4 and CHBr3 concentrations in the surface waters were 23.04 (6.04-107.81), 18.81 (10.67-32.35), 3.72 (0.39-9.77) and 24.33 (13.44-33.01) pmol x L(-1), respectively. The concentrations of VHCs near shore were higher than those in the open sea. In the PN section the vertical distribution of VHCs had a common feature that the maxima appeared in the upper mixed layer. The distributions of the four kinds of VHCs were significantly influenced by the Yangtze River effluent, the Kuroshio water and biological activities. A marked positive correlation between the C2 HCl3 and C2Cl4 concentrations was observed in the surface waters, suggesting that they might have some common sources. Besides, a positive correlation was found between chlorophyll a (Chl-a) and CHBr3 concentrations in the surface seawater, indicating that phytoplankton biomass might play an important role in the distribution of CHBr3 in the study area. Our data indicated that the entire ECS shelf acted as a source for atmospheric CHCl3, C2 HCl3 and CHBr3 during the study period.