Development and application of a gas chromatography method for simultaneously measuring H₂ and CH₄ in hydrothermal plume samples

Abstract

A robust, simple and efficient gas chromatography (GC) method is presented for determining H 2 and CH 4 concentrations simultaneously in water samples. The GC system consists of one detector (pulsed discharge helium ionization detector-PDHID), two columns in two ovens, respectively, and two 2-position-6-port purge valves. In this method, H 2 and CH 4 in water samples were first extracted into the headspace of syringes, then injected into the GC system. Both H 2 and CH 4 were detected by a PDHID. The separation of CH 4 from O 2 and N 2 in seawater is achieved by switching the O 2 and N 2 out of the carrier gas flow at the appropriate time window. H 2 and CH 4 concentrations in water samples collected from hydrothermal plumes at the Southwest Indian Ridge were determined successfully using this method.

The Size Fractionation and Speciation of Iron in the Longqi Hydrothermal Plumes on the Southwest Indian Ridge

“…DFe constituted a significant portion of TFe, ranging from 39.8 to 65.0% (Table 2). These results agree with previous studies conducted at the same location (Wang et al, 2012) and other locations (Field & Sherrell, 2000;Kleint et al, 2016;Sands et al, 2012), which suggest that a considerable fraction of the vent-derived Fe was not oxidized and deposited near the venting sites and could persist in the dissolved phase. This is likely due to the presence of the organic ligands (as described in section 3.1) and CFe including colloidal Fe oxyhydroxides, sulfides, and organic Fe complexes in the dissolved phase.…”

“…The possible sources include diffuse flow adjacent to the high-temperature vents and/or in situ biological activities. Since the Longqi hydrothermal field was found in 2007 (Tao et al, 2012), various studies, including the physical, chemical, and biological characteristics of the hydrothermal fluids, plumes, and the diffuse flow, have been carried out (Ji et al, 2017;Li et al, 2014Li et al, , 2016Liao et al, 2016;Pan et al, 2016;Peng et al, 2011;Tao et al, 2012Tao et al, , 2014Wang et al, 2012Wang et al, , 2015. It was found that there were no significant differences in microbial compositions between the hydrothermal plume samples and the ambient seawater (Li et al, 2016).…”

Distribution and Succession of Microbial Communities Along the Dispersal Pathway of Hydrothermal Plumes on the Southwest Indian Ridge

“…Gas chromatography (GC) was used onboard to determine the concentrations of dissolved CH 4 in the water samples as described previously (Wang et al, 2015;. Generally, once the CTD rosette sampler came back to the deck, water samples for CH 4 measurement were first taken by transferring water from each depth into different 100 ml extraction bottles.…”

A diagnostic GDGT signature for the impact of hydrothermal activity on surface deposits at the Southwest Indian Ridge

“…5b), indicating an additional contribution. As hydrothermal plume samples collected from Dragon Vent Field have higher CH4 contents than background water, by at least one order of magnitude (Wang et al, 2015), it seems likely that archaea involved in methane production and consumption could have contributed to the iGDGT signature of Group 3, affecting both MIs and %GDGT-0. However, the elevated MIs can also be explained by environmental impacts on GDGT distributions, as discussed above.…”