Figure F37. Methane (CH4) concentration in sediments at Site 1251 based on headspace (HS) and PCS data. Estimated theoretical solubility of methane in pore water (extrapolated from values calculated for higher pressures (depths) (Handa, 1990; Duan et al., 1992) is shown and fields of dissolved methane (D), methane hydrate (H), and free methane (F) are depicted. The gray area indicates the uncertainties in the position of the boundaries. 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. PCS = pressure core sampler.

Figure F37. Methane (CH₄) concentration in sediments at Site 1251 based on headspace (HS) and PCS data. Estimated theoretical solubility of methane in pore water (extrapolated from values calculated for higher pressures (depths) (Handa, 1990; Duan et al., 1992) is shown and fields of dissolved methane (D), methane hydrate (H), and free methane (F) are depicted. The gray area indicates the uncertainties in the position of the boundaries. 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. PCS = pressure core sampler.