Compound-specific radiocarbon analysis of sedimentary fatty acids: Potential as a dating tool for lake sediments of Mt. Fuji volcanic region, Japan.

• Radiocarbon ages of individual fatty acids were measured in lake surface sediment. • Pre-aged materials significantly affect the age of sedimentary fatty acids. • C 16 acid provides reliable chronology only when it originates from aquatic sources. Compound-specific radiocarbon analysis (CSRA) is a promising tool for dating sediment sequences where traditional dating methods are impractical. However, the applicability of CSRA of short-chain fatty acids as a dating tool remains poorly understood, especially in lacustrine settings. Accordingly, we determined the radiocarbon content (Δ14C) of individual fatty acids in sediments of Lake Yamanaka (central Japan), as well as their stable carbon and hydrogen isotope ratios, to evaluate the potential of CSRA as a dating tool in volcanic lake environments. We found that the Δ14C values of plant-derived (C 24 , C 26 , and C 28) n -fatty acids (–99‰ to –149‰) were considerably lower than the Δ14C of charred plants (139‰) within the sediments and those of living aquatic plants (–52‰ to –58‰) in Lake Yamanaka, suggesting that contributions from pre-aged terrestrial and aquatic plant materials likely affect these acids. Similarly, the Δ14C of C 16 n -fatty acid (–95‰) in surface sediments was much lower than the Δ14C of modern aquatic plants (–52‰ to –58‰), as well as the Δ14C of dissolved organic carbon (DIC) in surface water (–48‰). Together with the stable isotope results, we conclude that in addition to autochthonous aquatic sources, contributions from pre-aged terrestrial carbon sources significantly affect the Δ14C of C 16 n -fatty acids. Comparing fatty acid Δ14C and concentration data across lakes within the Mt. Fuji region suggests that CSRA of the C 16 acid provides valid chronological information only when the C 16 originates exclusively from autochthonous aquatic sources, with minor allochthonous terrestrial input. [ABSTRACT FROM AUTHOR]