“…Using 14 C content in fatty acids, we could better discuss the biogeochemical cycle and fates of the terrestrial organic matter in the soil system. Although stable carbon isotopic composition (e.g., Hayes et al, 1990;Huang et al, 1996;Naraoka et al, 1999;Lichtfouse, 2000) and radiocarbon analyses (Pearson et al, 2001;Uchida et al, 2000Uchida et al, , 2001Smittenberg et al, 2006) of lipid class compounds have been reported in sediments, radiocarbon analysis of individual organic molecules has rarely been conducted in soil samples. Lichtfouse et al (1997a, b) determined molecular distribution, 13 C and 14 C of hydrocarbon fractions from modern soil samples, and provided some evidence on their fossil fuel origin.…”