Ooki Atsushi, Yokouchi Yoko
National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-0053, Japan.
Environ Sci Technol. 2008 Aug 1;42(15):5706-11. doi: 10.1021/es800912j.
Methods for determining volatile organic compounds (VOCs) in water and air are required so that the VOCs' fluxes in water environments can be estimated. We developed a silicone membrane tube equilibrator for collecting gas-phase samples containing VOCs at equilibrium with natural water. The equilibrator consists of six silicone tubes housed in a polyvinyl chloride pipe. Equilibrated air samples collected from the equilibrator were analyzed with an automated preconcentration gas chromatography-mass spectrometry system for hourly measurements of VOC partial pressures. The partial pressures of all the target VOCs reached equilibrium within 1 h in the equilibrator. The system was used to determine VOC partial pressures in Lake Kasumigaura, a shallow eutrophic lake with a high concentration of suspended particulate matter (SPM). Compressed air was used daily to remove SPM deposited on the inner wall of the equilibrator and to maintain the equilibrium conditions for more than a week without the need to shut the system down. CH2Br2, CHCl3, CHBrCl2, CH2BrCl, C2H5I, C2Cl4, CH3I, and CH3Br in the lake were supersaturated with respect to the air, whereas CH3CI was undersaturated. CHCl3 had the highest flux (6.2 nmol m(-2) hr(-1)) during the observation period.
为了估算水环境中挥发性有机化合物（VOCs）的通量，需要测定水和空气中VOCs的方法。我们开发了一种硅树脂膜管平衡器，用于收集与天然水达到平衡的含VOCs的气相样品。该平衡器由六个置于聚氯乙烯管中的硅树脂管组成。从平衡器收集的平衡空气样品用自动预浓缩气相色谱 - 质谱系统进行分析，以每小时测量VOC的分压。在平衡器中，所有目标VOC的分压在1小时内达到平衡。该系统用于测定霞浦湖（一个悬浮颗粒物（SPM）浓度高的浅水富营养湖）中的VOC分压。每天使用压缩空气去除沉积在平衡器内壁上的SPM，并维持平衡条件一周以上而无需关闭系统。湖中CH2Br2、CHCl3、CHBrCl2、CH2BrCl、C2H5I、C2Cl4、CH3I和CH3Br相对于空气过饱和，而CH3CI不饱和。在观测期内，CHCl3的通量最高（6.2 nmol m(-2) hr(-1)）。
