2014 年 48 巻 2 号 p. 53-66
In this paper, we introduce a novel measurement technique, equilibrator inlet-proton transfer reaction-mass spectrometry (EI-PTR-MS), developed for continuous and in-situ determining volatile organic compounds (VOCs) dissolved in surface seawater. EI-PTR-MS consists of a PTR-MS to detect VOCs in gas phase and a bubbling-type equilibrator to extract VOCs from liquid phase to gas phase continuously. We confirmed that the EI-PTR-MS has high sensitivity and quick response time enough to monitor multiple VOCs dissolved in surface seawater. For dimethyl sulfide (DMS) and isoprene, comparisons of EI-PTR-MS measurements with those obtained with a conventional gas chromatography system showed generally good agreements. The high-resolution measurements by EI-PTR-MS enable us to detect the continuous variations in concentrations of VOCs during oceanic observations. Especially, there were large variations in the concentrations of DMS and the several regionally elevated peaks, “DMS hot spots” during a cruise in the western subarctic Pacific. We found that DMS and isoprene concentrations are highly correlated with the net community production, a parameter that integrates biological activity in the western subarctic Pacific and the Southern Ocean, respectively. We proposed that EI-PTR-MS could be one of the useful tools to improve both understandings of VOC production/consumption processes in ocean surface, which are important factors to predict future climate change.
