[M-IS05] Cenozoic Evolution of the Asian Monsoon and the Indo-Pacific Paleoclimates

[MIS05-P02] Human activities during last 700 years as recorded in the concentrations of polycyclic aromatic hydrocarbons and pentacyclic triterpene methyl ethers in sediment cores from Lake Suigetsu

*Masaya Inagaki¹, Hideto Nakamura², Masanobu Yamamoto¹, Takeshi Nakagawa³ (1.Graduate School of Environmental Science, Hokkaido University, 2.Faculty of Science, Osaka City University, 3.Research Center for Palaeoclimatorogy, Ritsumeikan University)

Polycyclic aromatic hydrocarbons (PAHs) are formed by burning of biomass or fossil fuel. Pentacyclic triterpene methyl ethers (PTMEs) are biomarkers that typically derive from graminoid plants. The presence of these compounds indicates human activities, for example, industrial burning, agriculture, and so on. In this study, we analyzed PAHs and PTMEs in sediment cores (SG06 and SG17 LIMNOS cores) from Lake Suigetsu in Fukui Prefecture. The concentration of PAHs peaks around 1945 C.E., indicating intense biomass burning near the study site. We suppose that this reflects the structural fires caused by air-attacks in the neighboring cities such as Tsuruga and Maizuru. The ratio of specific PAHs changed during the studied period, suggesting changes in the usage of biomass and fossil fuels. The relative amount of PTMEs, i.e., Sawamilletin and Miliacin, changed in 1320 C.E. and 1530 C.E. This suggests a change in graminoid vegetation around the study site, which might be related to historical shifts in cropping system.