氟氯烃（chlorofluorocarbons, CFCs）和六氟化硫（sulfur hexafluoride，SF₆）都是人工合成的卤代化合物，其在海洋科学考察中是非常重要的基础观测参数，在示踪海/气交换、水团交换等一系列重要海洋学过程研究中均有特殊的应用价值；同时，也可以用于估算表观耗氧速率（apparent oxygen utilization rate, AOUR）以及人为碳（anthropogenic CO₂, C_ant）等一些重要的物理及生物地球化学过程参量。较之CFCs，SF₆在海水中的浓度更低，测量难度更大，而CFCs和SF₆的联合使用对海洋学过程研究具有重大意义。本研究建立了一套吹扫捕集系统以分析海水中CFC-12和SF₆，对吹扫捕集系统测定条件进行了优化。本方法测定简单、灵敏，CFC-12、SF₆的检出限分别为0.02 pmol kg^-1、0.03 fmol kg^-1。本方法成功应用于2014年中国第六次北极科学考察航次、2015年基金委南海西部航次、2016年基金委南海中部航次、2016年基金委西太平洋航次以及2016年中国第七北极科学考察航次采集的海水样品的测定。相关文章《吹扫捕集-气相色谱法同时测定海水中的氟氯烃和六氟化硫》于2016年7月发表于《分析化学》期刊，并同步发表于英文版《Chinese Journal of Analytical Chemistry》期刊。

Fig. 1 Diagram of purge and trap system for CFC-12 and SF₆ measurement

Abstract:

Chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF₆) are kinds of anthropogenic halogenated compounds. They are very important for the ocean processes including air-sea exchange, water mass exchange etc. Meanwhile, they can be used to calculate some key physical and biogeochemical parameters such as AOUR (apparent oxygen utilization rate) and Cant (anthropogenic CO2). In comparison with CFCs, it is quite difficult to measure SF6 in the seawater due to its low solubility. However, it is useful to study the oceanic processes based on both the CFCs and SF₆. In this study, a purge and trap gas chromatographic system was developed to measure the CFC-12 and SF₆ simultaneously in seawater. The optimum conditions were as follows:trap temperature of -70℃, purge time of 8 min, purge gas pressure of 310 kPa, desorption time of 30 s, and desorption temperature of 90℃. The detection limit of CFC-12 and SF6 were 0.02 pmol/kg and 0.03 fmol/kg, respectively. The analytical precisions of CFC-12 and SF6 were ±1.2% and ±0.5%, respectively. The correlation coefficients (R2) of all the calibration curves were greater than 0.9995. This method was successfully used in the analysis of the samples collected from 6th Chinese Arctic Research Expedition.