IODP Expedition 329 Dissolved hydrogen gas (H2)

Dissolved hydrogen measured using a reduced gas analyzer (RGA, Trace Analytical Inc). Subcores were taken with 10 cm^3 cut-off syringes either on the catwalk or in a core refrigerator. The 10 cm^3 subcores were immediately extruded into 40 mL capacity screw-cap vials and filled with water. Samples for H2 analysis were taken next to whole-round cores used for interstitial water analysis. A headspace was created in the vial by introducing 500 μL of N2 gas. The samples were stored upside down for 10–20 h to allow the H2 to partition into the headspace. Just prior sampling, the vials were centrifuged (2 min at 200× g) to move the sediment away from the septa. Afterward, 500 μL of the headspace was extracted and injected on the RGA.