| 1) Tritiated sodium borohydride (NaBH4) was used to generate tritiated hydrogen gas (HT). Sodium borohydride [3H-] (NET-023A; Perkin Elmer) was dissolved into 0.1-N NaOH. NaBH4 is stable in alkaline conditions and decomposes upon acidification. 1.8 nmol of NaBH4 was transferred to 20-mL headspace vials and sealed (crimp cap). The solution was acidified by injecting H2SO4 through the septum. |
| 2) Syringe subsamples of sediment cores were placed into 2.0-mL headspace vials. After sealing, the vials were flushed with He gas and transferred to the radioisotope van. |
| 3) Tritiated H2 gas (x 400 µL) was injected into the vials through the septum. |
| 4) The vials were incubated at near in situ temperature in the radioisotope van. |
| 5) The incubations were terminated by injecting HgCl2 and returned for shore-based processing. |