Compound-Specific Radiocarbon Analysis of Organic Compounds from Mount Fuji Proximal Lake (Lake Kawaguchi) Sediment, Central Japan
Shinya Yamamoto, Yosuke Miyairi, Yūsuke Yokoyama, Hisami Suga, Nanako O. Ogawa, Naohiko Ohkouchi
Abstract
ABSTRACT Differential sources of sedimentary organic compounds in a volcanic region were revealed by determining radiocarbon content (Δ 14 C) of organic compounds in surface sediments from Lake Kawaguchi, at the northern foot of Mount Fuji, central Japan. The Δ 14 C values of C 16 fatty acid (−124‰) and chlorophyll a (Chl a ) (−133‰) were similar to the Δ 14 C of dissolved inorganic carbon (DIC) in surface water (−117‰), suggesting that a significant portion of these compounds originated from modern primary producers with a reservoir age of ~1000 years. On the other hand, a large offset between the Δ 14 C values of Chl a (−133‰) and those of 13 2 , 17 3 -cyclopheophorbide- a -enol (−169‰) and pheophytin a (−179‰) suggested contributions from older pigments. In addition, the Δ 14 C of long-chain (C 24 , C 26 , and C 28 ) fatty acids (−183 to −75‰) showed a large offset from that of a plant leaf remain (0‰) within sediments, demonstrating that the long-chain fatty acids were affected by substantial contributions from pre-aged terrestrial materials. Overall, the sedimentary organic compounds gave 14 C ages older than the plant leaf fragment within sediments; however, the similarity between Δ 14 C of the C 16 fatty acid and DIC implies potential for applying compound-specific radiocarbon analysis as a dating tool in volcanic lake environments.