Figure F46. Methane (CH4) concentration in sediments based on headspace (HS) and pressure core sampler (PCS) data at Site 1245. 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. Shaded area = 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.

Figure F46. Methane (CH₄) concentration in sediments based on headspace (HS) and pressure core sampler (PCS) data at Site 1245. 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. Shaded area = 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.