Continuous High-Frequency Dissolved O2/Ar Measurements by Equilibrator Inlet Mass Spectrometry

被引：101

作者：

Cassar, Nicolas ^{[1
]}

Barnett, Bruce A. ^{[1
]}

Bender, Michael L. ^{[1
]}

Kaiser, Jan ^{[2
]}

Hamme, Roberta C. ^{[3
]}

Tilbrook, Bronte ^{[4
,5
]}

机构：

[1] Princeton Univ, Dept Geosci, Princeton, NJ 08544 USA

[2] Univ E Anglia, Sch Environm Sci, Norwich NR4 7TJ, Norfolk, England

[3] Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC V8W 3P6, Canada

[4] CSIRO, Wealth Oceans Res Program, Hobart, Tas 7001, Australia

[5] CSIRO, Antarctic Climate & Ecosyst Cooperat Res Ctr, Hobart, Tas 7001, Australia

来源：

ANALYTICAL CHEMISTRY | 2009年 / 81卷 / 05期

关键词：

TRIPLE ISOTOPE COMPOSITION; SOUTHERN-OCEAN; GAS-EXCHANGE; DIFFUSION COEFFICIENTS; MEMBRANE CONTACTORS; METABOLIC BALANCE; WIND-SPEED; OXYGEN; WATER; SEA;

D O I：

10.1021/ac802300u

中图分类号：

O65 [分析化学];

学科分类号：

070302 ; 081704 ;

摘要：

The oxygen (O-2) concentration in the surface ocean is influenced by biological and physical processes. With concurrent measurements of argon (Ar), which has similar solubility properties as oxygen, we can remove the physical contribution to O-2 supersdturation and determine the biological oxygen supersaturation. Biological O-2 supersaturation in the surface ocean reflects the net metabolic balance between photosynthesis and respiration, i.e., the net community productivity (NCP). We present a new method for continuous shipboard measurements of O-2/Ar by equilibrator inlet mass spectrometry (EIMS). From these measurements and an appropriate gas exchange parametrization, NCP can be estimated at high spatial and temporal resolution. In the EIMS configuration, seawater from the ship's continuous intake flows through a cartridge enclosing a gas-permeable microporous membrane contactor. Gases in the headspace of the cartridge equilibrate with dissolved gases in the flowing seawater. A fused-silica capillary continuously samples headspace gases, and the O-2/Ar ratio is measured by mass spectrometry. The ion current measurements on the mass spectrometer reflect the partial pressures of dissolved gases in the water flowing through the equilibrator. Calibration of the O-2/Ar ion current ratio (32/40) is performed automatically every 2 h by sampling ambient air through a second capillary. A conceptual model demonstrates that the ratio of gases reaching the mass spectrometer is dependent on several parameters, such as the differences in molecular diffusivities and solubilities of the gases. Laboratory experiments and field observations performed by EIMS are discussed. We also present preliminary evidence that other gas measurements, such as N-2/Ar and PCO2 measurements, may potentially be performed with EIMS. Finally, we compare the characteristics of the EIMS with the previously described membrane inlet mass spectrometry (MIMS) approach.

引用

页码：1855 / 1864

页数：10