High-Frequency Spectrophotometric Measurements of Total Dissolved Inorganic Carbon in Seawater
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- 作者：Zhaohui Aleck Wang ; Sophie N. Chu ; Katherine A. Hoering
- 刊名：Environmental Science & Technology (ES&T)
- 出版年：2013
- 出版时间：July 16, 2013
- 年：2013
- 卷：47
- 期：14
- 页码：7840-7847
- 全文大小：398K
- 年卷期：v.47,no.14(July 16, 2013)
- ISSN：1520-5851
文摘
A new spectrophotometric method was developed to achieve continuous measurements of total dissolved inorganic carbon (DIC) in seawater. It uses a countercurrent flow design and a highly CO2-permeable membrane (Teflon AF 2400) to achieve flow-through CO2 equilibration between an acidified sample and an indicator solution with a fast response time of 22 s. This method improves the spatiotemporal resolution by more than 1 order of magnitude compared to the existing spectrophotometric method. The flow-through equilibration allows for continuous (1 Hz) detection and real-time data smoothing. The method had a short-term precision of 卤2.0 渭mol kg鈥? for a given flow-through sample. It achieved a field precision of 卤3.6 渭mol kg鈥? and successfully captured high DIC variability down to minute scales. Measurements by the new method over the typical range of oceanic DIC showed good agreement with measurements made by an established method (mean differences 鈭?.6 to 0.3 渭mol kg鈥? with 1蟽 卤 6.0鈥?.7 渭mol kg鈥?). This level of precision and accuracy is comparable to that of the existing spectrophotometric method. The characteristics of the new method make it particularly suitable for high-frequency, submerged measurements required for mobile observing platforms in the ocean. It can also be adapted for high-frequency, spectrophotometric measurements of seawater CO2 fugacity.