A simple headspace equilibration method for measuring dissolved methane

被引:109
作者
Magen, Cedric [1 ,2 ]
Lapham, Laura L. [2 ]
Pohlman, John W. [3 ]
Marshall, Kathleen [2 ]
Bosman, Samantha [1 ]
Casso, Michael [3 ]
Chanton, Jeffrey P. [1 ]
机构
[1] Florida State Univ, Tallahassee, FL 32306 USA
[2] Univ Maryland, Ctr Environm Sci, Chesapeake Biol Lab, Solomons, MD 20688 USA
[3] US Geol Survey, Woods Hole Coastal & Marine Sci Ctr, Woods Hole, MA 02543 USA
来源
LIMNOLOGY AND OCEANOGRAPHY-METHODS | 2014年 / 12卷
关键词
WATER COLUMN; OXIDATION; CONSUMPTION; SEDIMENTS; ATMOSPHERE; FLUXES; CARBON; RIVER; FATE;
D O I
10.4319/lom.2014.12.637
中图分类号
Q [生物科学];
学科分类号
07 ; 0710 ; 09 ;
摘要
Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yield, contamination issues during collection, transport and storage, and the effect of temperature changes and preservative. Previous extraction methods transfer methane from water to gas by either a "sparge and trap" or a "headspace equilibration" technique. The gas is then analyzed for methane by gas chromatography. Here, we revisit the headspace equilibration technique and describe a simple, inexpensive, and reliable method to measure methane in fresh and seawater, regardless of concentration. Within the range of concentrations typically found in surface seawaters (2-1000 nmol L-1), the yield of the method nears 100% of what is expected from solubility calculation following the addition of known amount of methane. In addition to being sensitive (detection limit of 0.1 ppmv, or 0.74 nmol L-1), this method requires less than 10 min per sample, and does not use highly toxic chemicals. It can be conducted with minimum materials and does not require the use of a gas chromatograph at the collection site. It can therefore be used in various remote working environments and conditions.
引用
收藏
页码:637 / 650
页数:14
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