Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS06] Biogeochemistry

Sun. May 22, 2016 1:45 PM - 3:15 PM A03 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Muneoki Yoh(Tokyo University of Agriculture and Technology), Hideaki Shibata(Field Science Center fot Northern Biosphere, Hokkaido University), Naohiko Ohkouchi(Japan Agency for Marine-Earth Science and Technology), Youhei Yamashita(Faculty of Environmental Earth Science, Hokkaido University), Chair:Yoshiyuki Inagaki(Forestry and Forest Products Research Institute), Kazumichi Fujii(Forestry and Forest Products Research Institute), Rota Wagai(National Institute for Agro-Environmental Sciences, Carbon & Nutrient Cycling Division), Kazuya Nishina(National Institute for Enviromental Studies)

2:45 PM - 3:00 PM

[MIS06-17] What physicochemical properties better explain the long-term biodegradability of burning-derived char?

*Masako Kajiura1, Rota Wagai1 (1.National Institute for Agro-Environmental Sciences)

Keywords:char, carbon sequestration, burning

Fires and field burnings produce char, which represents an important carbon (C) sink due to its high stability against biodegradation. Yet its potential for long-term C sequestration remains elusive as char has large variation in terms of physical and chemical properties depending on source material type and burning conditions. We thus need biodegradability indices that are applicable for the range of chars. The O/C molar ratio has often been used in the literature. On the other hand, H/C molar ratio better correlates with char’s chemical composition which is likely to control biological stability against microbial degradation. We thus tested if H/C ratio serves as a better index of the biodegradability than O/C ratio by comparing the chars prepared under different conditions (200–600 ºC, with/without heating temperature duration, low and ambient O2 levels) from rice straw and husk. We assessed their physicochemical characteristics and chemical composition using solid-state CP/MAS 13C-NMR. Based on 295-day laboratory incubation, we obtained biodegradability at three time scales: short (<100 d), intermediate (295 d), and long (>500 d) using inter- and extrapolation of decay curves. The short-term biodegradability was better explained by O/C ratio whereas the long-term biodegradability was better explained by H/C ratio. The H/C strongly correlated with aromatic and O-alkyl C, while O/C correlated with carboxylic C as well, suggesting that O/C reflected the amount of labile organic matters such as organic acids. Our findings suggest that long-term C fate of burning products is better estimated by H/C ratio rather than O/C ratio at least for the rice residues.