Figure F30. Methane concentration in sediments at Site 1249 based on headspace (HS) and pressure core sampler (PCS) data. Estimated theoretical solubility of methane in pore water (extrapolated from values calculated for higher pressures) (Handa, 1990; Duan et al., 1992) is shown, and fields of dissolved methane (D), methane hydrate (H), and free methane (F) are depicted. Note that the headspace technique fails to determine accurate concentration values above ~2 mM because methane is relatively abundant in situ and it rapidly escapes from sediments upon core retrieval.

Figure F30. Methane concentration in sediments at Site 1249 based on headspace (HS) and pressure core sampler (PCS) data. Estimated theoretical solubility of methane in pore water (extrapolated from values calculated for higher pressures) (Handa, 1990; Duan et al., 1992) is shown, and fields of dissolved methane (D), methane hydrate (H), and free methane (F) are depicted. Note that the headspace technique fails to determine accurate concentration values above ~2 mM because methane is relatively abundant in situ and it rapidly escapes from sediments upon core retrieval.