G05_P07
Isotopic signatures of fine organic aerosol in the deciduous forest and photosynthetic isotopic discrimination: Insights from compound-specific radiocarbon analysis
Uchida M1, Kumata H, Kondo M3,4, Chikaraishi Y5, Murayama S6, Mantoku K1, Kobayashi T1, Kawamura K5, Saigusa N1, Koizumi H3,8, Shibata Y9
1Earth System Division, National Institute For Environmental Studies, Tsukuba, Japan, 2Faculty of Life Science, Tokyo University of Pharmacy and Life Science, , Japan, 3River Basin Research Center, Gifu University, , Japan, 4Now at Health and Environmental Risk Division, National Institute For Environmental Studies, Tsukuba, Japan, 5 Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan, 6National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan, 7River Basin Research Center, Gifu University, , Japan, 8Now at Waseda University, , Japan, 9Tokyo University of Science, , Japan
Organic aerosols including secondary organic aerosols have serious impacts on the Earth’s climate system directly by scattering and absorbing solar radiation and indirectly by acting as cloud condensation nuclei. Forests release large amounts of volatile organic compounds into the atmosphere. However, the sources and fate of organic compounds of biogenic origin in a forest ecosystem are not yet well understood. This knowledge is also of importance to well understanding accurate carbon isotopic discrimination (Δ) by photosynthesis at the ecosystem scale for modeling terrestrial uptake of carbon dioxide. To understand the origin and fate of biogenic organic compounds in forest aerosol, we measured stable carbon isotopic ratios (δ¹³C) and radiocarbon (¹⁴C) contents of n-fatty acids, n-alkanes, and total organic carbon in forest aerosols, soil, and plant material as well as atmospheric CO₂. Fine aerosol samples (PM₁₀) were collected at few-week intervals from August 2003 to November 2004 during the growing season at Takayama Experimental site (36˚80’N, 137˚26’E, 1420m a.s.l.) in a cool-temperate deciduous forest in Japan. Based on the results obtained, we discuss the sources and turnover time, and temporal variations of forest organic molecules as well as estimated plant wax-based photosynthetic isotopic discrimination(Δ) .