冬季中国东海海水中挥发性卤代烃的分布特征和海-气通量

Distribution Characteristics and Sea-Air Fluxes of Volatile Halocarbons in the East China Sea in Winter

挥发性卤代烃是大气中重要的痕量温室气体,对全球变暖和大气化学具有重要作用.运用吹扫-捕集气相色谱法于2009年12月23日～2010年1月5日对中国东海表层海水和PN断面不同深度海水中4种挥发性卤代烃(VHCs)进行了测定,并对其来源进行了分析.结果表明,表层海水中CHCl3、C2HCl3、C2Cl4和CHBr3浓度平均值及范围分别为23.04 pmol·L-1(6.04～107.81 pmol·L-1)、18.18 pmol·L-1(10.67～32.35 pmol·L-1)、3.72 pmol·L-1(0.39～9.77 pmol·L-1)和24.33 pmol·L-1(13.44～33.01 pmol·L-1).4种VHCs浓度水平分布总体呈现近岸高、外海低的趋势;PN断面4种VHCs的浓度最大值出现在上混合层(50 m以浅).4种VHCs浓度的分布总体上受到长江冲淡水和黑潮水及生物活动的共同影响.相关性分析结果表明,C2HCl3与C2Cl4浓度呈现显著正相关,推测二者存在相似的来源;CHBr3浓度与叶绿素a浓度呈现一定的正相关性,推测CHBr3分布受到浮游植物生物量的影响.海-气通量估算表明,冬季调查海域是大气中CHCl3、C2HCl3和CHBr3的源.

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 , C2HCl3 , C2Cl4 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, C2HCl3 , C2Cl4 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·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 Karoshio water and biological activities. A marked positive correlation between the C2HCl3 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 , C2HCl3 and CHBr3during the study period.