Carbon isotope composition of CH4 from rice paddies in Japan |
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Authors: | Minoru Uzaki Hiroshi Mizutani Eitaro Wada |
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Institution: | (1) Laboratory of Biogeochemistry and Sociogeochemistry, Mitsubishi Kasei Institute of Life Sciences, 11 Minamiooya, Machida, Tokyo, 194, Japan |
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Abstract: | Carbon isotope ratios (13C) for bubble CH4 in a submerged paddy soil were studied in Yokohama, Japan, throughout a growing period, and its variation was found. Bubble CH4 collected from other 33 paddy fields in Japan was also measured for its 13C and the results agreed with Yokohama. Furthermore, the variation occurred irrespective of the amount and the type of supplied organic substances to the fields (whole rice straw, rice stubble, or compost). The 13C value (average value of -55.9 ± 4.24) from these paddy fields was higher than those of the CH4 emitted from African and North American paddies. The higher value was little affected by their difference in the supplied organic substances. CH4 oxidation likely occurs for bubble CH4 in the shallow paddy fields. A rough estimate of the total CH4 production, using isotope mass balance, showed that 17 to 22% of organic carbon supplied to Japanese paddies transforms to CH4. |
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Keywords: | carbon isotope ratio methane rice field seasonal variation |
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